/*
 * f_mass_storage.c -- Mass Storage USB Composite Function
 *
 * Copyright (C) 2003-2008 Alan Stern
 * Copyright (C) 2009 Samsung Electronics
 *                    Author: Michal Nazarewicz <mina86@mina86.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The names of the above-listed copyright holders may not be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * ALTERNATIVELY, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") as published by the Free Software
 * Foundation, either version 2 of that License or (at your option) any
 * later version.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * The Mass Storage Function acts as a USB Mass Storage device,
 * appearing to the host as a disk drive or as a CD-ROM drive.  In
 * addition to providing an example of a genuinely useful composite
 * function for a USB device, it also illustrates a technique of
 * double-buffering for increased throughput.
 *
 * For more information about MSF and in particular its module
 * parameters and sysfs interface read the
 * <Documentation/usb/mass-storage.txt> file.
 */

/*
 * MSF is configured by specifying a fsg_config structure.  It has the
 * following fields:
 *
 *      nluns           Number of LUNs function have (anywhere from 1
 *                              to FSG_MAX_LUNS).
 *      luns            An array of LUN configuration values.  This
 *                              should be filled for each LUN that
 *                              function will include (ie. for "nluns"
 *                              LUNs).  Each element of the array has
 *                              the following fields:
 *      ->filename      The path to the backing file for the LUN.
 *                              Required if LUN is not marked as
 *                              removable.
 *      ->ro            Flag specifying access to the LUN shall be
 *                              read-only.  This is implied if CD-ROM
 *                              emulation is enabled as well as when
 *                              it was impossible to open "filename"
 *                              in R/W mode.
 *      ->removable     Flag specifying that LUN shall be indicated as
 *                              being removable.
 *      ->cdrom         Flag specifying that LUN shall be reported as
 *                              being a CD-ROM.
 *      ->nofua         Flag specifying that FUA flag in SCSI WRITE(10,12)
 *                              commands for this LUN shall be ignored.
 *
 *      vendor_name
 *      product_name
 *      release         Information used as a reply to INQUIRY
 *                              request.  To use default set to NULL,
 *                              NULL, 0xffff respectively.  The first
 *                              field should be 8 and the second 16
 *                              characters or less.
 *
 *      can_stall       Set to permit function to halt bulk endpoints.
 *                              Disabled on some USB devices known not
 *                              to work correctly.  You should set it
 *                              to true.
 *
 * If "removable" is not set for a LUN then a backing file must be
 * specified.  If it is set, then NULL filename means the LUN's medium
 * is not loaded (an empty string as "filename" in the fsg_config
 * structure causes error).  The CD-ROM emulation includes a single
 * data track and no audio tracks; hence there need be only one
 * backing file per LUN.
 *
 * This function is heavily based on "File-backed Storage Gadget" by
 * Alan Stern which in turn is heavily based on "Gadget Zero" by David
 * Brownell.  The driver's SCSI command interface was based on the
 * "Information technology - Small Computer System Interface - 2"
 * document from X3T9.2 Project 375D, Revision 10L, 7-SEP-93,
 * available at <http://www.t10.org/ftp/t10/drafts/s2/s2-r10l.pdf>.
 * The single exception is opcode 0x23 (READ FORMAT CAPACITIES), which
 * was based on the "Universal Serial Bus Mass Storage Class UFI
 * Command Specification" document, Revision 1.0, December 14, 1998,
 * available at
 * <http://www.usb.org/developers/devclass_docs/usbmass-ufi10.pdf>.
 */

/*
 *                              Driver Design
 *
 * The MSF is fairly straightforward.  There is a main kernel
 * thread that handles most of the work.  Interrupt routines field
 * callbacks from the controller driver: bulk- and interrupt-request
 * completion notifications, endpoint-0 events, and disconnect events.
 * Completion events are passed to the main thread by wakeup calls.  Many
 * ep0 requests are handled at interrupt time, but SetInterface,
 * SetConfiguration, and device reset requests are forwarded to the
 * thread in the form of "exceptions" using SIGUSR1 signals (since they
 * should interrupt any ongoing file I/O operations).
 *
 * The thread's main routine implements the standard command/data/status
 * parts of a SCSI interaction.  It and its subroutines are full of tests
 * for pending signals/exceptions -- all this polling is necessary since
 * the kernel has no setjmp/longjmp equivalents.  (Maybe this is an
 * indication that the driver really wants to be running in userspace.)
 * An important point is that so long as the thread is alive it keeps an
 * open reference to the backing file.  This will prevent unmounting
 * the backing file's underlying filesystem and could cause problems
 * during system shutdown, for example.  To prevent such problems, the
 * thread catches INT, TERM, and KILL signals and converts them into
 * an EXIT exception.
 *
 * In normal operation the main thread is started during the gadget's
 * fsg_bind() callback and stopped during fsg_unbind().  But it can
 * also exit when it receives a signal, and there's no point leaving
 * the gadget running when the thread is dead.  As of this moment, MSF
 * provides no way to deregister the gadget when thread dies -- maybe
 * a callback functions is needed.
 *
 * To provide maximum throughput, the driver uses a circular pipeline of
 * buffer heads (struct fsg_buffhd).  In principle the pipeline can be
 * arbitrarily long; in practice the benefits don't justify having more
 * than 2 stages (i.e., double buffering).  But it helps to think of the
 * pipeline as being a long one.  Each buffer head contains a bulk-in and
 * a bulk-out request pointer (since the buffer can be used for both
 * output and input -- directions always are given from the host's
 * point of view) as well as a pointer to the buffer and various state
 * variables.
 *
 * Use of the pipeline follows a simple protocol.  There is a variable
 * (fsg->next_buffhd_to_fill) that points to the next buffer head to use.
 * At any time that buffer head may still be in use from an earlier
 * request, so each buffer head has a state variable indicating whether
 * it is EMPTY, FULL, or BUSY.  Typical use involves waiting for the
 * buffer head to be EMPTY, filling the buffer either by file I/O or by
 * USB I/O (during which the buffer head is BUSY), and marking the buffer
 * head FULL when the I/O is complete.  Then the buffer will be emptied
 * (again possibly by USB I/O, during which it is marked BUSY) and
 * finally marked EMPTY again (possibly by a completion routine).
 *
 * A module parameter tells the driver to avoid stalling the bulk
 * endpoints wherever the transport specification allows.  This is
 * necessary for some UDCs like the SuperH, which cannot reliably clear a
 * halt on a bulk endpoint.  However, under certain circumstances the
 * Bulk-only specification requires a stall.  In such cases the driver
 * will halt the endpoint and set a flag indicating that it should clear
 * the halt in software during the next device reset.  Hopefully this
 * will permit everything to work correctly.  Furthermore, although the
 * specification allows the bulk-out endpoint to halt when the host sends
 * too much data, implementing this would cause an unavoidable race.
 * The driver will always use the "no-stall" approach for OUT transfers.
 *
 * One subtle point concerns sending status-stage responses for ep0
 * requests.  Some of these requests, such as device reset, can involve
 * interrupting an ongoing file I/O operation, which might take an
 * arbitrarily long time.  During that delay the host might give up on
 * the original ep0 request and issue a new one.  When that happens the
 * driver should not notify the host about completion of the original
 * request, as the host will no longer be waiting for it.  So the driver
 * assigns to each ep0 request a unique tag, and it keeps track of the
 * tag value of the request associated with a long-running exception
 * (device-reset, interface-change, or configuration-change).  When the
 * exception handler is finished, the status-stage response is submitted
 * only if the current ep0 request tag is equal to the exception request
 * tag.  Thus only the most recently received ep0 request will get a
 * status-stage response.
 *
 * Warning: This driver source file is too long.  It ought to be split up
 * into a header file plus about 3 separate .c files, to handle the details
 * of the Gadget, USB Mass Storage, and SCSI protocols.
 */


/* #define VERBOSE_DEBUG */
/* #define DUMP_MSGS */

#include <linux/blkdev.h>
#include <linux/completion.h>
#include <linux/dcache.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/kref.h>
#include <linux/kthread.h>
#include <linux/sched/signal.h>
#include <linux/limits.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/freezer.h>
#include <linux/module.h>
#include <linux/uaccess.h>

#include <linux/usb/ch9.h>
#include <linux/usb/gadget.h>
#include <linux/usb/composite.h>

#include "configfs.h"


/*------------------------------------------------------------------------*/

#define FSG_DRIVER_DESC         "Mass Storage Function"
#define FSG_DRIVER_VERSION      "2009/09/11"

static const char fsg_string_interface[] = "Mass Storage";

#include "storage_common.h"
#include "f_mass_storage.h"

/* Static strings, in UTF-8 (for simplicity we use only ASCII characters) */
static struct usb_string                fsg_strings[] = {
        {FSG_STRING_INTERFACE,          fsg_string_interface},
        {}
};

static struct usb_gadget_strings        fsg_stringtab = {
        .language       = 0x0409,               /* en-us */
        .strings        = fsg_strings,
};

static struct usb_gadget_strings *fsg_strings_array[] = {
        &fsg_stringtab,
        NULL,
};

/*-------------------------------------------------------------------------*/

struct fsg_dev;
struct fsg_common;

/* Data shared by all the FSG instances. */
struct fsg_common {
        struct usb_gadget       *gadget;
        struct usb_composite_dev *cdev;
        struct fsg_dev          *fsg, *new_fsg;
        wait_queue_head_t       io_wait;
        wait_queue_head_t       fsg_wait;

        /* filesem protects: backing files in use */
        struct rw_semaphore     filesem;

        /* lock protects: state and thread_task */
        spinlock_t              lock;

        struct usb_ep           *ep0;           /* Copy of gadget->ep0 */
        struct usb_request      *ep0req;        /* Copy of cdev->req */
        unsigned int            ep0_req_tag;

        struct fsg_buffhd       *next_buffhd_to_fill;
        struct fsg_buffhd       *next_buffhd_to_drain;
        struct fsg_buffhd       *buffhds;
        unsigned int            fsg_num_buffers;

        int                     cmnd_size;
        u8                      cmnd[MAX_COMMAND_SIZE];

        unsigned int            lun;
        struct fsg_lun          *luns[FSG_MAX_LUNS];
        struct fsg_lun          *curlun;

        unsigned int            bulk_out_maxpacket;
        enum fsg_state          state;          /* For exception handling */
        unsigned int            exception_req_tag;

        enum data_direction     data_dir;
        u32                     data_size;
        u32                     data_size_from_cmnd;
        u32                     tag;
        u32                     residue;
        u32                     usb_amount_left;

        unsigned int            can_stall:1;
        unsigned int            free_storage_on_release:1;
        unsigned int            phase_error:1;
        unsigned int            short_packet_received:1;
        unsigned int            bad_lun_okay:1;
        unsigned int            running:1;
        unsigned int            sysfs:1;

        struct completion       thread_notifier;
        struct task_struct      *thread_task;

        /* Callback functions. */
        const struct fsg_operations     *ops;
        /* Gadget's private data. */
        void                    *private_data;

        char inquiry_string[INQUIRY_STRING_LEN];

        struct kref             ref;
};

struct fsg_dev {
        struct usb_function     function;
        struct usb_gadget       *gadget;        /* Copy of cdev->gadget */
        struct fsg_common       *common;

        u16                     interface_number;

        unsigned int            bulk_in_enabled:1;
        unsigned int            bulk_out_enabled:1;

        unsigned long           atomic_bitflags;
#define IGNORE_BULK_OUT         0

        struct usb_ep           *bulk_in;
        struct usb_ep           *bulk_out;
};

static inline int __fsg_is_set(struct fsg_common *common,
                               const char *func, unsigned line)
{
        if (common->fsg)
                return 1;
        ERROR(common, "common->fsg is NULL in %s at %u\n", func, line);
        WARN_ON(1);
        return 0;
}

#define fsg_is_set(common) likely(__fsg_is_set(common, __func__, __LINE__))

static inline struct fsg_dev *fsg_from_func(struct usb_function *f)
{
        return container_of(f, struct fsg_dev, function);
}

typedef void (*fsg_routine_t)(struct fsg_dev *);

static int exception_in_progress(struct fsg_common *common)
{
        return common->state > FSG_STATE_NORMAL;
}

/* Make bulk-out requests be divisible by the maxpacket size */
static void set_bulk_out_req_length(struct fsg_common *common,
                                    struct fsg_buffhd *bh, unsigned int length)
{
        unsigned int    rem;

        bh->bulk_out_intended_length = length;
        rem = length % common->bulk_out_maxpacket;
        if (rem > 0)
                length += common->bulk_out_maxpacket - rem;
        bh->outreq->length = length;
}


/*-------------------------------------------------------------------------*/

static int fsg_set_halt(struct fsg_dev *fsg, struct usb_ep *ep)
{
        const char      *name;

        if (ep == fsg->bulk_in)
                name = "bulk-in";
        else if (ep == fsg->bulk_out)
                name = "bulk-out";
        else
                name = ep->name;
        DBG(fsg, "%s set halt\n", name);
        return usb_ep_set_halt(ep);
}


/*-------------------------------------------------------------------------*/

/* These routines may be called in process context or in_irq */

static void raise_exception(struct fsg_common *common, enum fsg_state new_state)
{
        unsigned long           flags;

        /*
         * Do nothing if a higher-priority exception is already in progress.
         * If a lower-or-equal priority exception is in progress, preempt it
         * and notify the main thread by sending it a signal.
         */
        spin_lock_irqsave(&common->lock, flags);
        if (common->state <= new_state) {
                common->exception_req_tag = common->ep0_req_tag;
                common->state = new_state;
                if (common->thread_task)
                        send_sig_info(SIGUSR1, SEND_SIG_FORCED,
                                      common->thread_task);
        }
        spin_unlock_irqrestore(&common->lock, flags);
}


/*-------------------------------------------------------------------------*/

static int ep0_queue(struct fsg_common *common)
{
        int     rc;

        rc = usb_ep_queue(common->ep0, common->ep0req, GFP_ATOMIC);
        common->ep0->driver_data = common;
        if (rc != 0 && rc != -ESHUTDOWN) {
                /* We can't do much more than wait for a reset */
                WARNING(common, "error in submission: %s --> %d\n",
                        common->ep0->name, rc);
        }
        return rc;
}


/*-------------------------------------------------------------------------*/

/* Completion handlers. These always run in_irq. */

static void bulk_in_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct fsg_common       *common = ep->driver_data;
        struct fsg_buffhd       *bh = req->context;

        if (req->status || req->actual != req->length)
                DBG(common, "%s --> %d, %u/%u\n", __func__,
                    req->status, req->actual, req->length);
        if (req->status == -ECONNRESET)         /* Request was cancelled */
                usb_ep_fifo_flush(ep);

        /* Synchronize with the smp_load_acquire() in sleep_thread() */
        smp_store_release(&bh->state, BUF_STATE_EMPTY);
        wake_up(&common->io_wait);
}

static void bulk_out_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct fsg_common       *common = ep->driver_data;
        struct fsg_buffhd       *bh = req->context;

        dump_msg(common, "bulk-out", req->buf, req->actual);
        if (req->status || req->actual != bh->bulk_out_intended_length)
                DBG(common, "%s --> %d, %u/%u\n", __func__,
                    req->status, req->actual, bh->bulk_out_intended_length);
        if (req->status == -ECONNRESET)         /* Request was cancelled */
                usb_ep_fifo_flush(ep);

        /* Synchronize with the smp_load_acquire() in sleep_thread() */
        smp_store_release(&bh->state, BUF_STATE_FULL);
        wake_up(&common->io_wait);
}

static int _fsg_common_get_max_lun(struct fsg_common *common)
{
        int i = ARRAY_SIZE(common->luns) - 1;

        while (i >= 0 && !common->luns[i])
                --i;

        return i;
}

static int fsg_setup(struct usb_function *f,
                     const struct usb_ctrlrequest *ctrl)
{
        struct fsg_dev          *fsg = fsg_from_func(f);
        struct usb_request      *req = fsg->common->ep0req;
        u16                     w_index = le16_to_cpu(ctrl->wIndex);
        u16                     w_value = le16_to_cpu(ctrl->wValue);
        u16                     w_length = le16_to_cpu(ctrl->wLength);

        if (!fsg_is_set(fsg->common))
                return -EOPNOTSUPP;

        ++fsg->common->ep0_req_tag;     /* Record arrival of a new request */
        req->context = NULL;
        req->length = 0;
        dump_msg(fsg, "ep0-setup", (u8 *) ctrl, sizeof(*ctrl));

        switch (ctrl->bRequest) {

        case US_BULK_RESET_REQUEST:
                if (ctrl->bRequestType !=
                    (USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                        break;
                if (w_index != fsg->interface_number || w_value != 0 ||
                                w_length != 0)
                        return -EDOM;

                /*
                 * Raise an exception to stop the current operation
                 * and reinitialize our state.
                 */
                DBG(fsg, "bulk reset request\n");
                raise_exception(fsg->common, FSG_STATE_PROTOCOL_RESET);
                return USB_GADGET_DELAYED_STATUS;

        case US_BULK_GET_MAX_LUN:
                if (ctrl->bRequestType !=
                    (USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                        break;
                if (w_index != fsg->interface_number || w_value != 0 ||
                                w_length != 1)
                        return -EDOM;
                VDBG(fsg, "get max LUN\n");
                *(u8 *)req->buf = _fsg_common_get_max_lun(fsg->common);

                /* Respond with data/status */
                req->length = min((u16)1, w_length);
                return ep0_queue(fsg->common);
        }

        VDBG(fsg,
             "unknown class-specific control req %02x.%02x v%04x i%04x l%u\n",
             ctrl->bRequestType, ctrl->bRequest,
             le16_to_cpu(ctrl->wValue), w_index, w_length);
        return -EOPNOTSUPP;
}


/*-------------------------------------------------------------------------*/

/* All the following routines run in process context */

/* Use this for bulk or interrupt transfers, not ep0 */
static int start_transfer(struct fsg_dev *fsg, struct usb_ep *ep,
                           struct usb_request *req)
{
        int     rc;

        if (ep == fsg->bulk_in)
                dump_msg(fsg, "bulk-in", req->buf, req->length);

        rc = usb_ep_queue(ep, req, GFP_KERNEL);
        if (rc) {

                /* We can't do much more than wait for a reset */
                req->status = rc;

                /*
                 * Note: currently the net2280 driver fails zero-length
                 * submissions if DMA is enabled.
                 */
                if (rc != -ESHUTDOWN &&
                                !(rc == -EOPNOTSUPP && req->length == 0))
                        WARNING(fsg, "error in submission: %s --> %d\n",
                                        ep->name, rc);
        }
        return rc;
}

static bool start_in_transfer(struct fsg_common *common, struct fsg_buffhd *bh)
{
        if (!fsg_is_set(common))
                return false;
        bh->state = BUF_STATE_SENDING;
        if (start_transfer(common->fsg, common->fsg->bulk_in, bh->inreq))
                bh->state = BUF_STATE_EMPTY;
        return true;
}

static bool start_out_transfer(struct fsg_common *common, struct fsg_buffhd *bh)
{
        if (!fsg_is_set(common))
                return false;
        bh->state = BUF_STATE_RECEIVING;
        if (start_transfer(common->fsg, common->fsg->bulk_out, bh->outreq))
                bh->state = BUF_STATE_FULL;
        return true;
}

static int sleep_thread(struct fsg_common *common, bool can_freeze,
                struct fsg_buffhd *bh)
{
        int     rc;

        /* Wait until a signal arrives or bh is no longer busy */
        if (can_freeze)
                /*
                 * synchronize with the smp_store_release(&bh->state) in
                 * bulk_in_complete() or bulk_out_complete()
                 */
                rc = wait_event_freezable(common->io_wait,
                                bh && smp_load_acquire(&bh->state) >=
                                        BUF_STATE_EMPTY);
        else
                rc = wait_event_interruptible(common->io_wait,
                                bh && smp_load_acquire(&bh->state) >=
                                        BUF_STATE_EMPTY);
        return rc ? -EINTR : 0;
}


/*-------------------------------------------------------------------------*/

static int do_read(struct fsg_common *common)
{
        struct fsg_lun          *curlun = common->curlun;
        u32                     lba;
        struct fsg_buffhd       *bh;
        int                     rc;
        u32                     amount_left;
        loff_t                  file_offset, file_offset_tmp;
        unsigned int            amount;
        ssize_t                 nread;

        /*
         * Get the starting Logical Block Address and check that it's
         * not too big.
         */
        if (common->cmnd[0] == READ_6)
                lba = get_unaligned_be24(&common->cmnd[1]);
        else {
                lba = get_unaligned_be32(&common->cmnd[2]);

                /*
                 * We allow DPO (Disable Page Out = don't save data in the
                 * cache) and FUA (Force Unit Access = don't read from the
                 * cache), but we don't implement them.
                 */
                if ((common->cmnd[1] & ~0x18) != 0) {
                        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
        }
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }
        file_offset = ((loff_t) lba) << curlun->blkbits;

        /* Carry out the file reads */
        amount_left = common->data_size_from_cmnd;
        if (unlikely(amount_left == 0))
                return -EIO;            /* No default reply */

        for (;;) {
                /*
                 * Figure out how much we need to read:
                 * Try to read the remaining amount.
                 * But don't read more than the buffer size.
                 * And don't try to read past the end of the file.
                 */
                amount = min(amount_left, FSG_BUFLEN);
                amount = min((loff_t)amount,
                             curlun->file_length - file_offset);

                /* Wait for the next buffer to become available */
                bh = common->next_buffhd_to_fill;
                rc = sleep_thread(common, false, bh);
                if (rc)
                        return rc;

                /*
                 * If we were asked to read past the end of file,
                 * end with an empty buffer.
                 */
                if (amount == 0) {
                        curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                        curlun->sense_data_info =
                                        file_offset >> curlun->blkbits;
                        curlun->info_valid = 1;
                        bh->inreq->length = 0;
                        bh->state = BUF_STATE_FULL;
                        break;
                }

                /* Perform the read */
                file_offset_tmp = file_offset;
                nread = vfs_read(curlun->filp,
                                 (char __user *)bh->buf,
                                 amount, &file_offset_tmp);
                VLDBG(curlun, "file read %u @ %llu -> %d\n", amount,
                      (unsigned long long)file_offset, (int)nread);
                if (signal_pending(current))
                        return -EINTR;

                if (nread < 0) {
                        LDBG(curlun, "error in file read: %d\n", (int)nread);
                        nread = 0;
                } else if (nread < amount) {
                        LDBG(curlun, "partial file read: %d/%u\n",
                             (int)nread, amount);
                        nread = round_down(nread, curlun->blksize);
                }
                file_offset  += nread;
                amount_left  -= nread;
                common->residue -= nread;

                /*
                 * Except at the end of the transfer, nread will be
                 * equal to the buffer size, which is divisible by the
                 * bulk-in maxpacket size.
                 */
                bh->inreq->length = nread;
                bh->state = BUF_STATE_FULL;

                /* If an error occurred, report it and its position */
                if (nread < amount) {
                        curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
                        curlun->sense_data_info =
                                        file_offset >> curlun->blkbits;
                        curlun->info_valid = 1;
                        break;
                }

                if (amount_left == 0)
                        break;          /* No more left to read */

                /* Send this buffer and go read some more */
                bh->inreq->zero = 0;
                if (!start_in_transfer(common, bh))
                        /* Don't know what to do if common->fsg is NULL */
                        return -EIO;
                common->next_buffhd_to_fill = bh->next;
        }

        return -EIO;            /* No default reply */
}


/*-------------------------------------------------------------------------*/

static int do_write(struct fsg_common *common)
{
        struct fsg_lun          *curlun = common->curlun;
        u32                     lba;
        struct fsg_buffhd       *bh;
        int                     get_some_more;
        u32                     amount_left_to_req, amount_left_to_write;
        loff_t                  usb_offset, file_offset, file_offset_tmp;
        unsigned int            amount;
        ssize_t                 nwritten;
        int                     rc;

        if (curlun->ro) {
                curlun->sense_data = SS_WRITE_PROTECTED;
                return -EINVAL;
        }
        spin_lock(&curlun->filp->f_lock);
        curlun->filp->f_flags &= ~O_SYNC;       /* Default is not to wait */
        spin_unlock(&curlun->filp->f_lock);

        /*
         * Get the starting Logical Block Address and check that it's
         * not too big
         */
        if (common->cmnd[0] == WRITE_6)
                lba = get_unaligned_be24(&common->cmnd[1]);
        else {
                lba = get_unaligned_be32(&common->cmnd[2]);

                /*
                 * We allow DPO (Disable Page Out = don't save data in the
                 * cache) and FUA (Force Unit Access = write directly to the
                 * medium).  We don't implement DPO; we implement FUA by
                 * performing synchronous output.
                 */
                if (common->cmnd[1] & ~0x18) {
                        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
                if (!curlun->nofua && (common->cmnd[1] & 0x08)) { /* FUA */
                        spin_lock(&curlun->filp->f_lock);
                        curlun->filp->f_flags |= O_SYNC;
                        spin_unlock(&curlun->filp->f_lock);
                }
        }
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }

        /* Carry out the file writes */
        get_some_more = 1;
        file_offset = usb_offset = ((loff_t) lba) << curlun->blkbits;
        amount_left_to_req = common->data_size_from_cmnd;
        amount_left_to_write = common->data_size_from_cmnd;

        while (amount_left_to_write > 0) {

                /* Queue a request for more data from the host */
                bh = common->next_buffhd_to_fill;
                if (bh->state == BUF_STATE_EMPTY && get_some_more) {

                        /*
                         * Figure out how much we want to get:
                         * Try to get the remaining amount,
                         * but not more than the buffer size.
                         */
                        amount = min(amount_left_to_req, FSG_BUFLEN);

                        /* Beyond the end of the backing file? */
                        if (usb_offset >= curlun->file_length) {
                                get_some_more = 0;
                                curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                                curlun->sense_data_info =
                                        usb_offset >> curlun->blkbits;
                                curlun->info_valid = 1;
                                continue;
                        }

                        /* Get the next buffer */
                        usb_offset += amount;
                        common->usb_amount_left -= amount;
                        amount_left_to_req -= amount;
                        if (amount_left_to_req == 0)
                                get_some_more = 0;

                        /*
                         * Except at the end of the transfer, amount will be
                         * equal to the buffer size, which is divisible by
                         * the bulk-out maxpacket size.
                         */
                        set_bulk_out_req_length(common, bh, amount);
                        if (!start_out_transfer(common, bh))
                                /* Dunno what to do if common->fsg is NULL */
                                return -EIO;
                        common->next_buffhd_to_fill = bh->next;
                        continue;
                }

                /* Write the received data to the backing file */
                bh = common->next_buffhd_to_drain;
                if (bh->state == BUF_STATE_EMPTY && !get_some_more)
                        break;                  /* We stopped early */

                /* Wait for the data to be received */
                rc = sleep_thread(common, false, bh);
                if (rc)
                        return rc;

                common->next_buffhd_to_drain = bh->next;
                bh->state = BUF_STATE_EMPTY;

                /* Did something go wrong with the transfer? */
                if (bh->outreq->status != 0) {
                        curlun->sense_data = SS_COMMUNICATION_FAILURE;
                        curlun->sense_data_info =
                                        file_offset >> curlun->blkbits;
                        curlun->info_valid = 1;
                        break;
                }

                amount = bh->outreq->actual;
                if (curlun->file_length - file_offset < amount) {
                        LERROR(curlun, "write %u @ %llu beyond end %llu\n",
                                       amount, (unsigned long long)file_offset,
                                       (unsigned long long)curlun->file_length);
                        amount = curlun->file_length - file_offset;
                }

                /*
                 * Don't accept excess data.  The spec doesn't say
                 * what to do in this case.  We'll ignore the error.
                 */
                amount = min(amount, bh->bulk_out_intended_length);

                /* Don't write a partial block */
                amount = round_down(amount, curlun->blksize);
                if (amount == 0)
                        goto empty_write;

                /* Perform the write */
                file_offset_tmp = file_offset;
                nwritten = vfs_write(curlun->filp, (char __user *)bh->buf,
                                amount, &file_offset_tmp);
                VLDBG(curlun, "file write %u @ %llu -> %d\n", amount,
                                (unsigned long long)file_offset, (int)nwritten);
                if (signal_pending(current))
                        return -EINTR;          /* Interrupted! */

                if (nwritten < 0) {
                        LDBG(curlun, "error in file write: %d\n",
                                        (int) nwritten);
                        nwritten = 0;
                } else if (nwritten < amount) {
                        LDBG(curlun, "partial file write: %d/%u\n",
                                        (int) nwritten, amount);
                        nwritten = round_down(nwritten, curlun->blksize);
                }
                file_offset += nwritten;
                amount_left_to_write -= nwritten;
                common->residue -= nwritten;

                /* If an error occurred, report it and its position */
                if (nwritten < amount) {
                        curlun->sense_data = SS_WRITE_ERROR;
                        curlun->sense_data_info =
                                        file_offset >> curlun->blkbits;
                        curlun->info_valid = 1;
                        break;
                }

 empty_write:
                /* Did the host decide to stop early? */
                if (bh->outreq->actual < bh->bulk_out_intended_length) {
                        common->short_packet_received = 1;
                        break;
                }
        }

        return -EIO;            /* No default reply */
}


/*-------------------------------------------------------------------------*/

static int do_synchronize_cache(struct fsg_common *common)
{
        struct fsg_lun  *curlun = common->curlun;
        int             rc;

        /* We ignore the requested LBA and write out all file's
         * dirty data buffers. */
        rc = fsg_lun_fsync_sub(curlun);
        if (rc)
                curlun->sense_data = SS_WRITE_ERROR;
        return 0;
}


/*-------------------------------------------------------------------------*/

static void invalidate_sub(struct fsg_lun *curlun)
{
        struct file     *filp = curlun->filp;
        struct inode    *inode = file_inode(filp);
        unsigned long   rc;

        rc = invalidate_mapping_pages(inode->i_mapping, 0, -1);
        VLDBG(curlun, "invalidate_mapping_pages -> %ld\n", rc);
}

static int do_verify(struct fsg_common *common)
{
        struct fsg_lun          *curlun = common->curlun;
        u32                     lba;
        u32                     verification_length;
        struct fsg_buffhd       *bh = common->next_buffhd_to_fill;
        loff_t                  file_offset, file_offset_tmp;
        u32                     amount_left;
        unsigned int            amount;
        ssize_t                 nread;

        /*
         * Get the starting Logical Block Address and check that it's
         * not too big.
         */
        lba = get_unaligned_be32(&common->cmnd[2]);
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }

        /*
         * We allow DPO (Disable Page Out = don't save data in the
         * cache) but we don't implement it.
         */
        if (common->cmnd[1] & ~0x10) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        verification_length = get_unaligned_be16(&common->cmnd[7]);
        if (unlikely(verification_length == 0))
                return -EIO;            /* No default reply */

        /* Prepare to carry out the file verify */
        amount_left = verification_length << curlun->blkbits;
        file_offset = ((loff_t) lba) << curlun->blkbits;

        /* Write out all the dirty buffers before invalidating them */
        fsg_lun_fsync_sub(curlun);
        if (signal_pending(current))
                return -EINTR;

        invalidate_sub(curlun);
        if (signal_pending(current))
                return -EINTR;

        /* Just try to read the requested blocks */
        while (amount_left > 0) {
                /*
                 * Figure out how much we need to read:
                 * Try to read the remaining amount, but not more than
                 * the buffer size.
                 * And don't try to read past the end of the file.
                 */
                amount = min(amount_left, FSG_BUFLEN);
                amount = min((loff_t)amount,
                             curlun->file_length - file_offset);
                if (amount == 0) {
                        curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                        curlun->sense_data_info =
                                file_offset >> curlun->blkbits;
                        curlun->info_valid = 1;
                        break;
                }

                /* Perform the read */
                file_offset_tmp = file_offset;
                nread = vfs_read(curlun->filp,
                                (char __user *) bh->buf,
                                amount, &file_offset_tmp);
                VLDBG(curlun, "file read %u @ %llu -> %d\n", amount,
                                (unsigned long long) file_offset,
                                (int) nread);
                if (signal_pending(current))
                        return -EINTR;

                if (nread < 0) {
                        LDBG(curlun, "error in file verify: %d\n", (int)nread);
                        nread = 0;
                } else if (nread < amount) {
                        LDBG(curlun, "partial file verify: %d/%u\n",
                             (int)nread, amount);
                        nread = round_down(nread, curlun->blksize);
                }
                if (nread == 0) {
                        curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
                        curlun->sense_data_info =
                                file_offset >> curlun->blkbits;
                        curlun->info_valid = 1;
                        break;
                }
                file_offset += nread;
                amount_left -= nread;
        }
        return 0;
}


/*-------------------------------------------------------------------------*/

static int do_inquiry(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun *curlun = common->curlun;
        u8      *buf = (u8 *) bh->buf;

        if (!curlun) {          /* Unsupported LUNs are okay */
                common->bad_lun_okay = 1;
                memset(buf, 0, 36);
                buf[0] = TYPE_NO_LUN;   /* Unsupported, no device-type */
                buf[4] = 31;            /* Additional length */
                return 36;
        }

        buf[0] = curlun->cdrom ? TYPE_ROM : TYPE_DISK;
        buf[1] = curlun->removable ? 0x80 : 0;
        buf[2] = 2;             /* ANSI SCSI level 2 */
        buf[3] = 2;             /* SCSI-2 INQUIRY data format */
        buf[4] = 31;            /* Additional length */
        buf[5] = 0;             /* No special options */
        buf[6] = 0;
        buf[7] = 0;
        if (curlun->inquiry_string[0])
                memcpy(buf + 8, curlun->inquiry_string,
                       sizeof(curlun->inquiry_string));
        else
                memcpy(buf + 8, common->inquiry_string,
                       sizeof(common->inquiry_string));
        return 36;
}

static int do_request_sense(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = common->curlun;
        u8              *buf = (u8 *) bh->buf;
        u32             sd, sdinfo;
        int             valid;

        /*
         * From the SCSI-2 spec., section 7.9 (Unit attention condition):
         *
         * If a REQUEST SENSE command is received from an initiator
         * with a pending unit attention condition (before the target
         * generates the contingent allegiance condition), then the
         * target shall either:
         *   a) report any pending sense data and preserve the unit
         *      attention condition on the logical unit, or,
         *   b) report the unit attention condition, may discard any
         *      pending sense data, and clear the unit attention
         *      condition on the logical unit for that initiator.
         *
         * FSG normally uses option a); enable this code to use option b).
         */
#if 0
        if (curlun && curlun->unit_attention_data != SS_NO_SENSE) {
                curlun->sense_data = curlun->unit_attention_data;
                curlun->unit_attention_data = SS_NO_SENSE;
        }
#endif

        if (!curlun) {          /* Unsupported LUNs are okay */
                common->bad_lun_okay = 1;
                sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;
                sdinfo = 0;
                valid = 0;
        } else {
                sd = curlun->sense_data;
                sdinfo = curlun->sense_data_info;
                valid = curlun->info_valid << 7;
                curlun->sense_data = SS_NO_SENSE;
                curlun->sense_data_info = 0;
                curlun->info_valid = 0;
        }

        memset(buf, 0, 18);
        buf[0] = valid | 0x70;                  /* Valid, current error */
        buf[2] = SK(sd);
        put_unaligned_be32(sdinfo, &buf[3]);    /* Sense information */
        buf[7] = 18 - 8;                        /* Additional sense length */
        buf[12] = ASC(sd);
        buf[13] = ASCQ(sd);
        return 18;
}

static int do_read_capacity(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = common->curlun;
        u32             lba = get_unaligned_be32(&common->cmnd[2]);
        int             pmi = common->cmnd[8];
        u8              *buf = (u8 *)bh->buf;

        /* Check the PMI and LBA fields */
        if (pmi > 1 || (pmi == 0 && lba != 0)) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        put_unaligned_be32(curlun->num_sectors - 1, &buf[0]);
                                                /* Max logical block */
        put_unaligned_be32(curlun->blksize, &buf[4]);/* Block length */
        return 8;
}

static int do_read_header(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = common->curlun;
        int             msf = common->cmnd[1] & 0x02;
        u32             lba = get_unaligned_be32(&common->cmnd[2]);
        u8              *buf = (u8 *)bh->buf;

        if (common->cmnd[1] & ~0x02) {          /* Mask away MSF */
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }

        memset(buf, 0, 8);
        buf[0] = 0x01;          /* 2048 bytes of user data, rest is EC */
        store_cdrom_address(&buf[4], msf, lba);
        return 8;
}

static int do_read_toc(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = common->curlun;
        int             msf = common->cmnd[1] & 0x02;
        int             start_track = common->cmnd[6];
        u8              *buf = (u8 *)bh->buf;

        if ((common->cmnd[1] & ~0x02) != 0 ||   /* Mask away MSF */
                        start_track > 1) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        memset(buf, 0, 20);
        buf[1] = (20-2);                /* TOC data length */
        buf[2] = 1;                     /* First track number */
        buf[3] = 1;                     /* Last track number */
        buf[5] = 0x16;                  /* Data track, copying allowed */
        buf[6] = 0x01;                  /* Only track is number 1 */
        store_cdrom_address(&buf[8], msf, 0);

        buf[13] = 0x16;                 /* Lead-out track is data */
        buf[14] = 0xAA;                 /* Lead-out track number */
        store_cdrom_address(&buf[16], msf, curlun->num_sectors);
        return 20;
}

static int do_mode_sense(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = common->curlun;
        int             mscmnd = common->cmnd[0];
        u8              *buf = (u8 *) bh->buf;
        u8              *buf0 = buf;
        int             pc, page_code;
        int             changeable_values, all_pages;
        int             valid_page = 0;
        int             len, limit;

        if ((common->cmnd[1] & ~0x08) != 0) {   /* Mask away DBD */
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }
        pc = common->cmnd[2] >> 6;
        page_code = common->cmnd[2] & 0x3f;
        if (pc == 3) {
                curlun->sense_data = SS_SAVING_PARAMETERS_NOT_SUPPORTED;
                return -EINVAL;
        }
        changeable_values = (pc == 1);
        all_pages = (page_code == 0x3f);

        /*
         * Write the mode parameter header.  Fixed values are: default
         * medium type, no cache control (DPOFUA), and no block descriptors.
         * The only variable value is the WriteProtect bit.  We will fill in
         * the mode data length later.
         */
        memset(buf, 0, 8);
        if (mscmnd == MODE_SENSE) {
                buf[2] = (curlun->ro ? 0x80 : 0x00);            /* WP, DPOFUA */
                buf += 4;
                limit = 255;
        } else {                        /* MODE_SENSE_10 */
                buf[3] = (curlun->ro ? 0x80 : 0x00);            /* WP, DPOFUA */
                buf += 8;
                limit = 65535;          /* Should really be FSG_BUFLEN */
        }

        /* No block descriptors */

        /*
         * The mode pages, in numerical order.  The only page we support
         * is the Caching page.
         */
        if (page_code == 0x08 || all_pages) {
                valid_page = 1;
                buf[0] = 0x08;          /* Page code */
                buf[1] = 10;            /* Page length */
                memset(buf+2, 0, 10);   /* None of the fields are changeable */

                if (!changeable_values) {
                        buf[2] = 0x04;  /* Write cache enable, */
                                        /* Read cache not disabled */
                                        /* No cache retention priorities */
                        put_unaligned_be16(0xffff, &buf[4]);
                                        /* Don't disable prefetch */
                                        /* Minimum prefetch = 0 */
                        put_unaligned_be16(0xffff, &buf[8]);
                                        /* Maximum prefetch */
                        put_unaligned_be16(0xffff, &buf[10]);
                                        /* Maximum prefetch ceiling */
                }
                buf += 12;
        }

        /*
         * Check that a valid page was requested and the mode data length
         * isn't too long.
         */
        len = buf - buf0;
        if (!valid_page || len > limit) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        /*  Store the mode data length */
        if (mscmnd == MODE_SENSE)
                buf0[0] = len - 1;
        else
                put_unaligned_be16(len - 2, buf0);
        return len;
}

static int do_start_stop(struct fsg_common *common)
{
        struct fsg_lun  *curlun = common->curlun;
        int             loej, start;

        if (!curlun) {
                return -EINVAL;
        } else if (!curlun->removable) {
                curlun->sense_data = SS_INVALID_COMMAND;
                return -EINVAL;
        } else if ((common->cmnd[1] & ~0x01) != 0 || /* Mask away Immed */
                   (common->cmnd[4] & ~0x03) != 0) { /* Mask LoEj, Start */
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        loej  = common->cmnd[4] & 0x02;
        start = common->cmnd[4] & 0x01;

        /*
         * Our emulation doesn't support mounting; the medium is
         * available for use as soon as it is loaded.
         */
        if (start) {
                if (!fsg_lun_is_open(curlun)) {
                        curlun->sense_data = SS_MEDIUM_NOT_PRESENT;
                        return -EINVAL;
                }
                return 0;
        }

        /* Are we allowed to unload the media? */
        if (curlun->prevent_medium_removal) {
                LDBG(curlun, "unload attempt prevented\n");
                curlun->sense_data = SS_MEDIUM_REMOVAL_PREVENTED;
                return -EINVAL;
        }

        if (!loej)
                return 0;

        up_read(&common->filesem);
        down_write(&common->filesem);
        fsg_lun_close(curlun);
        up_write(&common->filesem);
        down_read(&common->filesem);

        return 0;
}

static int do_prevent_allow(struct fsg_common *common)
{
        struct fsg_lun  *curlun = common->curlun;
        int             prevent;

        if (!common->curlun) {
                return -EINVAL;
        } else if (!common->curlun->removable) {
                common->curlun->sense_data = SS_INVALID_COMMAND;
                return -EINVAL;
        }

        prevent = common->cmnd[4] & 0x01;
        if ((common->cmnd[4] & ~0x01) != 0) {   /* Mask away Prevent */
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        if (curlun->prevent_medium_removal && !prevent)
                fsg_lun_fsync_sub(curlun);
        curlun->prevent_medium_removal = prevent;
        return 0;
}

static int do_read_format_capacities(struct fsg_common *common,
                        struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = common->curlun;
        u8              *buf = (u8 *) bh->buf;

        buf[0] = buf[1] = buf[2] = 0;
        buf[3] = 8;     /* Only the Current/Maximum Capacity Descriptor */
        buf += 4;

        put_unaligned_be32(curlun->num_sectors, &buf[0]);
                                                /* Number of blocks */
        put_unaligned_be32(curlun->blksize, &buf[4]);/* Block length */
        buf[4] = 0x02;                          /* Current capacity */
        return 12;
}

static int do_mode_select(struct fsg_common *common, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = common->curlun;

        /* We don't support MODE SELECT */
        if (curlun)
                curlun->sense_data = SS_INVALID_COMMAND;
        return -EINVAL;
}


/*-------------------------------------------------------------------------*/

static int halt_bulk_in_endpoint(struct fsg_dev *fsg)
{
        int     rc;

        rc = fsg_set_halt(fsg, fsg->bulk_in);
        if (rc == -EAGAIN)
                VDBG(fsg, "delayed bulk-in endpoint halt\n");
        while (rc != 0) {
                if (rc != -EAGAIN) {
                        WARNING(fsg, "usb_ep_set_halt -> %d\n", rc);
                        rc = 0;
                        break;
                }

                /* Wait for a short time and then try again */
                if (msleep_interruptible(100) != 0)
                        return -EINTR;
                rc = usb_ep_set_halt(fsg->bulk_in);
        }
        return rc;
}

static int wedge_bulk_in_endpoint(struct fsg_dev *fsg)
{
        int     rc;

        DBG(fsg, "bulk-in set wedge\n");
        rc = usb_ep_set_wedge(fsg->bulk_in);
        if (rc == -EAGAIN)
                VDBG(fsg, "delayed bulk-in endpoint wedge\n");
        while (rc != 0) {
                if (rc != -EAGAIN) {
                        WARNING(fsg, "usb_ep_set_wedge -> %d\n", rc);
                        rc = 0;
                        break;
                }

                /* Wait for a short time and then try again */
                if (msleep_interruptible(100) != 0)
                        return -EINTR;
                rc = usb_ep_set_wedge(fsg->bulk_in);
        }
        return rc;
}

static int throw_away_data(struct fsg_common *common)
{
        struct fsg_buffhd       *bh, *bh2;
        u32                     amount;
        int                     rc;

        for (bh = common->next_buffhd_to_drain;
             bh->state != BUF_STATE_EMPTY || common->usb_amount_left > 0;
             bh = common->next_buffhd_to_drain) {

                /* Try to submit another request if we need one */
                bh2 = common->next_buffhd_to_fill;
                if (bh2->state == BUF_STATE_EMPTY &&
                                common->usb_amount_left > 0) {
                        amount = min(common->usb_amount_left, FSG_BUFLEN);

                        /*
                         * Except at the end of the transfer, amount will be
                         * equal to the buffer size, which is divisible by
                         * the bulk-out maxpacket size.
                         */
                        set_bulk_out_req_length(common, bh2, amount);
                        if (!start_out_transfer(common, bh2))
                                /* Dunno what to do if common->fsg is NULL */
                                return -EIO;
                        common->next_buffhd_to_fill = bh2->next;
                        common->usb_amount_left -= amount;
                        continue;
                }

                /* Wait for the data to be received */
                rc = sleep_thread(common, false, bh);
                if (rc)
                        return rc;

                /* Throw away the data in a filled buffer */
                bh->state = BUF_STATE_EMPTY;
                common->next_buffhd_to_drain = bh->next;

                /* A short packet or an error ends everything */
                if (bh->outreq->actual < bh->bulk_out_intended_length ||
                                bh->outreq->status != 0) {
                        raise_exception(common, FSG_STATE_ABORT_BULK_OUT);
                        return -EINTR;
                }
        }
        return 0;
}

static int finish_reply(struct fsg_common *common)
{
        struct fsg_buffhd       *bh = common->next_buffhd_to_fill;
        int                     rc = 0;

        switch (common->data_dir) {
        case DATA_DIR_NONE:
                break;                  /* Nothing to send */

        /*
         * If we don't know whether the host wants to read or write,
         * this must be CB or CBI with an unknown command.  We mustn't
         * try to send or receive any data.  So stall both bulk pipes
         * if we can and wait for a reset.
         */
        case DATA_DIR_UNKNOWN:
                if (!common->can_stall) {
                        /* Nothing */
                } else if (fsg_is_set(common)) {
                        fsg_set_halt(common->fsg, common->fsg->bulk_out);
                        rc = halt_bulk_in_endpoint(common->fsg);
                } else {
                        /* Don't know what to do if common->fsg is NULL */
                        rc = -EIO;
                }
                break;

        /* All but the last buffer of data must have already been sent */
        case DATA_DIR_TO_HOST:
                if (common->data_size == 0) {
                        /* Nothing to send */

                /* Don't know what to do if common->fsg is NULL */
                } else if (!fsg_is_set(common)) {
                        rc = -EIO;

                /* If there's no residue, simply send the last buffer */
                } else if (common->residue == 0) {
                        bh->inreq->zero = 0;
                        if (!start_in_transfer(common, bh))
                                return -EIO;
                        common->next_buffhd_to_fill = bh->next;

                /*
                 * For Bulk-only, mark the end of the data with a short
                 * packet.  If we are allowed to stall, halt the bulk-in
                 * endpoint.  (Note: This violates the Bulk-Only Transport
                 * specification, which requires us to pad the data if we
                 * don't halt the endpoint.  Presumably nobody will mind.)
                 */
                } else {
                        bh->inreq->zero = 1;
                        if (!start_in_transfer(common, bh))
                                rc = -EIO;
                        common->next_buffhd_to_fill = bh->next;
                        if (common->can_stall)
                                rc = halt_bulk_in_endpoint(common->fsg);
                }
                break;

        /*
         * We have processed all we want from the data the host has sent.
         * There may still be outstanding bulk-out requests.
         */
        case DATA_DIR_FROM_HOST:
                if (common->residue == 0) {
                        /* Nothing to receive */

                /* Did the host stop sending unexpectedly early? */
                } else if (common->short_packet_received) {
                        raise_exception(common, FSG_STATE_ABORT_BULK_OUT);
                        rc = -EINTR;

                /*
                 * We haven't processed all the incoming data.  Even though
                 * we may be allowed to stall, doing so would cause a race.
                 * The controller may already have ACK'ed all the remaining
                 * bulk-out packets, in which case the host wouldn't see a
                 * STALL.  Not realizing the endpoint was halted, it wouldn't
                 * clear the halt -- leading to problems later on.
                 */
#if 0
                } else if (common->can_stall) {
                        if (fsg_is_set(common))
                                fsg_set_halt(common->fsg,
                                             common->fsg->bulk_out);
                        raise_exception(common, FSG_STATE_ABORT_BULK_OUT);
                        rc = -EINTR;
#endif

                /*
                 * We can't stall.  Read in the excess data and throw it
                 * all away.
                 */
                } else {
                        rc = throw_away_data(common);
                }
                break;
        }
        return rc;
}

static void send_status(struct fsg_common *common)
{
        struct fsg_lun          *curlun = common->curlun;
        struct fsg_buffhd       *bh;
        struct bulk_cs_wrap     *csw;
        int                     rc;
        u8                      status = US_BULK_STAT_OK;
        u32                     sd, sdinfo = 0;

        /* Wait for the next buffer to become available */
        bh = common->next_buffhd_to_fill;
        rc = sleep_thread(common, false, bh);
        if (rc)
                return;

        if (curlun) {
                sd = curlun->sense_data;
                sdinfo = curlun->sense_data_info;
        } else if (common->bad_lun_okay)
                sd = SS_NO_SENSE;
        else
                sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;

        if (common->phase_error) {
                DBG(common, "sending phase-error status\n");
                status = US_BULK_STAT_PHASE;
                sd = SS_INVALID_COMMAND;
        } else if (sd != SS_NO_SENSE) {
                DBG(common, "sending command-failure status\n");
                status = US_BULK_STAT_FAIL;
                VDBG(common, "  sense data: SK x%02x, ASC x%02x, ASCQ x%02x;"
                                "  info x%x\n",
                                SK(sd), ASC(sd), ASCQ(sd), sdinfo);
        }

        /* Store and send the Bulk-only CSW */
        csw = (void *)bh->buf;

        csw->Signature = cpu_to_le32(US_BULK_CS_SIGN);
        csw->Tag = common->tag;
        csw->Residue = cpu_to_le32(common->residue);
        csw->Status = status;

        bh->inreq->length = US_BULK_CS_WRAP_LEN;
        bh->inreq->zero = 0;
        if (!start_in_transfer(common, bh))
                /* Don't know what to do if common->fsg is NULL */
                return;

        common->next_buffhd_to_fill = bh->next;
        return;
}


/*-------------------------------------------------------------------------*/

/*
 * Check whether the command is properly formed and whether its data size
 * and direction agree with the values we already have.
 */
static int check_command(struct fsg_common *common, int cmnd_size,
                         enum data_direction data_dir, unsigned int mask,
                         int needs_medium, const char *name)
{
        int                     i;
        unsigned int            lun = common->cmnd[1] >> 5;
        static const char       dirletter[4] = {'u', 'o', 'i', 'n'};
        char                    hdlen[20];
        struct fsg_lun          *curlun;

        hdlen[0] = 0;
        if (common->data_dir != DATA_DIR_UNKNOWN)
                sprintf(hdlen, ", H%c=%u", dirletter[(int) common->data_dir],
                        common->data_size);
        VDBG(common, "SCSI command: %s;  Dc=%d, D%c=%u;  Hc=%d%s\n",
             name, cmnd_size, dirletter[(int) data_dir],
             common->data_size_from_cmnd, common->cmnd_size, hdlen);

        /*
         * We can't reply at all until we know the correct data direction
         * and size.
         */
        if (common->data_size_from_cmnd == 0)
                data_dir = DATA_DIR_NONE;
        if (common->data_size < common->data_size_from_cmnd) {
                /*
                 * Host data size < Device data size is a phase error.
                 * Carry out the command, but only transfer as much as
                 * we are allowed.
                 */
                common->data_size_from_cmnd = common->data_size;
                common->phase_error = 1;
        }
        common->residue = common->data_size;
        common->usb_amount_left = common->data_size;

        /* Conflicting data directions is a phase error */
        if (common->data_dir != data_dir && common->data_size_from_cmnd > 0) {
                common->phase_error = 1;
                return -EINVAL;
        }

        /* Verify the length of the command itself */
        if (cmnd_size != common->cmnd_size) {

                /*
                 * Special case workaround: There are plenty of buggy SCSI
                 * implementations. Many have issues with cbw->Length
                 * field passing a wrong command size. For those cases we
                 * always try to work around the problem by using the length
                 * sent by the host side provided it is at least as large
                 * as the correct command length.
                 * Examples of such cases would be MS-Windows, which issues
                 * REQUEST SENSE with cbw->Length == 12 where it should
                 * be 6, and xbox360 issuing INQUIRY, TEST UNIT READY and
                 * REQUEST SENSE with cbw->Length == 10 where it should
                 * be 6 as well.
                 */
                if (cmnd_size <= common->cmnd_size) {
                        DBG(common, "%s is buggy! Expected length %d "
                            "but we got %d\n", name,
                            cmnd_size, common->cmnd_size);
                        cmnd_size = common->cmnd_size;
                } else {
                        common->phase_error = 1;
                        return -EINVAL;
                }
        }

        /* Check that the LUN values are consistent */
        if (common->lun != lun)
                DBG(common, "using LUN %u from CBW, not LUN %u from CDB\n",
                    common->lun, lun);

        /* Check the LUN */
        curlun = common->curlun;
        if (curlun) {
                if (common->cmnd[0] != REQUEST_SENSE) {
                        curlun->sense_data = SS_NO_SENSE;
                        curlun->sense_data_info = 0;
                        curlun->info_valid = 0;
                }
        } else {
                common->bad_lun_okay = 0;

                /*
                 * INQUIRY and REQUEST SENSE commands are explicitly allowed
                 * to use unsupported LUNs; all others may not.
                 */
                if (common->cmnd[0] != INQUIRY &&
                    common->cmnd[0] != REQUEST_SENSE) {
                        DBG(common, "unsupported LUN %u\n", common->lun);
                        return -EINVAL;
                }
        }

        /*
         * If a unit attention condition exists, only INQUIRY and
         * REQUEST SENSE commands are allowed; anything else must fail.
         */
        if (curlun && curlun->unit_attention_data != SS_NO_SENSE &&
            common->cmnd[0] != INQUIRY &&
            common->cmnd[0] != REQUEST_SENSE) {
                curlun->sense_data = curlun->unit_attention_data;
                curlun->unit_attention_data = SS_NO_SENSE;
                return -EINVAL;
        }

        /* Check that only command bytes listed in the mask are non-zero */
        common->cmnd[1] &= 0x1f;                        /* Mask away the LUN */
        for (i = 1; i < cmnd_size; ++i) {
                if (common->cmnd[i] && !(mask & (1 << i))) {
                        if (curlun)
                                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
        }

        /* If the medium isn't mounted and the command needs to access
         * it, return an error. */
        if (curlun && !fsg_lun_is_open(curlun) && needs_medium) {
                curlun->sense_data = SS_MEDIUM_NOT_PRESENT;
                return -EINVAL;
        }

        return 0;
}

/* wrapper of check_command for data size in blocks handling */
static int check_command_size_in_blocks(struct fsg_common *common,
                int cmnd_size, enum data_direction data_dir,
                unsigned int mask, int needs_medium, const char *name)
{
        if (common->curlun)
                common->data_size_from_cmnd <<= common->curlun->blkbits;
        return check_command(common, cmnd_size, data_dir,
                        mask, needs_medium, name);
}

static int do_scsi_command(struct fsg_common *common)
{
        struct fsg_buffhd       *bh;
        int                     rc;
        int                     reply = -EINVAL;
        int                     i;
        static char             unknown[16];

        dump_cdb(common);

        /* Wait for the next buffer to become available for data or status */
        bh = common->next_buffhd_to_fill;
        common->next_buffhd_to_drain = bh;
        rc = sleep_thread(common, false, bh);
        if (rc)
                return rc;

        common->phase_error = 0;
        common->short_packet_received = 0;

        down_read(&common->filesem);    /* We're using the backing file */
        switch (common->cmnd[0]) {

        case INQUIRY:
                common->data_size_from_cmnd = common->cmnd[4];
                reply = check_command(common, 6, DATA_DIR_TO_HOST,
                                      (1<<4), 0,
                                      "INQUIRY");
                if (reply == 0)
                        reply = do_inquiry(common, bh);
                break;

        case MODE_SELECT:
                common->data_size_from_cmnd = common->cmnd[4];
                reply = check_command(common, 6, DATA_DIR_FROM_HOST,
                                      (1<<1) | (1<<4), 0,
                                      "MODE SELECT(6)");
                if (reply == 0)
                        reply = do_mode_select(common, bh);
                break;

        case MODE_SELECT_10:
                common->data_size_from_cmnd =
                        get_unaligned_be16(&common->cmnd[7]);
                reply = check_command(common, 10, DATA_DIR_FROM_HOST,
                                      (1<<1) | (3<<7), 0,
                                      "MODE SELECT(10)");
                if (reply == 0)
                        reply = do_mode_select(common, bh);
                break;

        case MODE_SENSE:
                common->data_size_from_cmnd = common->cmnd[4];
                reply = check_command(common, 6, DATA_DIR_TO_HOST,
                                      (1<<1) | (1<<2) | (1<<4), 0,
                                      "MODE SENSE(6)");
                if (reply == 0)
                        reply = do_mode_sense(common, bh);
                break;

        case MODE_SENSE_10:
                common->data_size_from_cmnd =
                        get_unaligned_be16(&common->cmnd[7]);
                reply = check_command(common, 10, DATA_DIR_TO_HOST,
                                      (1<<1) | (1<<2) | (3<<7), 0,
                                      "MODE SENSE(10)");
                if (reply == 0)
                        reply = do_mode_sense(common, bh);
                break;

        case ALLOW_MEDIUM_REMOVAL:
                common->data_size_from_cmnd = 0;
                reply = check_command(common, 6, DATA_DIR_NONE,
                                      (1<<4), 0,
                                      "PREVENT-ALLOW MEDIUM REMOVAL");
                if (reply == 0)
                        reply = do_prevent_allow(common);
                break;

        case READ_6:
                i = common->cmnd[4];
                common->data_size_from_cmnd = (i == 0) ? 256 : i;
                reply = check_command_size_in_blocks(common, 6,
                                      DATA_DIR_TO_HOST,
                                      (7<<1) | (1<<4), 1,
                                      "READ(6)");
                if (reply == 0)
                        reply = do_read(common);
                break;

        case READ_10:
                common->data_size_from_cmnd =
                                get_unaligned_be16(&common->cmnd[7]);
                reply = check_command_size_in_blocks(common, 10,
                                      DATA_DIR_TO_HOST,
                                      (1<<1) | (0xf<<2) | (3<<7), 1,
                                      "READ(10)");
                if (reply == 0)
                        reply = do_read(common);
                break;

        case READ_12:
                common->data_size_from_cmnd =
                                get_unaligned_be32(&common->cmnd[6]);
                reply = check_command_size_in_blocks(common, 12,
                                      DATA_DIR_TO_HOST,
                                      (1<<1) | (0xf<<2) | (0xf<<6), 1,
                                      "READ(12)");
                if (reply == 0)
                        reply = do_read(common);
                break;

        case READ_CAPACITY:
                common->data_size_from_cmnd = 8;
                reply = check_command(common, 10, DATA_DIR_TO_HOST,
                                      (0xf<<2) | (1<<8), 1,
                                      "READ CAPACITY");
                if (reply == 0)
                        reply = do_read_capacity(common, bh);
                break;

        case READ_HEADER:
                if (!common->curlun || !common->curlun->cdrom)
                        goto unknown_cmnd;
                common->data_size_from_cmnd =
                        get_unaligned_be16(&common->cmnd[7]);
                reply = check_command(common, 10, DATA_DIR_TO_HOST,
                                      (3<<7) | (0x1f<<1), 1,
                                      "READ HEADER");
                if (reply == 0)
                        reply = do_read_header(common, bh);
                break;

        case READ_TOC:
                if (!common->curlun || !common->curlun->cdrom)
                        goto unknown_cmnd;
                common->data_size_from_cmnd =
                        get_unaligned_be16(&common->cmnd[7]);
                reply = check_command(common, 10, DATA_DIR_TO_HOST,
                                      (7<<6) | (1<<1), 1,
                                      "READ TOC");
                if (reply == 0)
                        reply = do_read_toc(common, bh);
                break;

        case READ_FORMAT_CAPACITIES:
                common->data_size_from_cmnd =
                        get_unaligned_be16(&common->cmnd[7]);
                reply = check_command(common, 10, DATA_DIR_TO_HOST,
                                      (3<<7), 1,
                                      "READ FORMAT CAPACITIES");
                if (reply == 0)
                        reply = do_read_format_capacities(common, bh);
                break;

        case REQUEST_SENSE:
                common->data_size_from_cmnd = common->cmnd[4];
                reply = check_command(common, 6, DATA_DIR_TO_HOST,
                                      (1<<4), 0,
                                      "REQUEST SENSE");
                if (reply == 0)
                        reply = do_request_sense(common, bh);
                break;

        case START_STOP:
                common->data_size_from_cmnd = 0;
                reply = check_command(common, 6, DATA_DIR_NONE,
                                      (1<<1) | (1<<4), 0,
                                      "START-STOP UNIT");
                if (reply == 0)
                        reply = do_start_stop(common);
                break;

        case SYNCHRONIZE_CACHE:
                common->data_size_from_cmnd = 0;
                reply = check_command(common, 10, DATA_DIR_NONE,
                                      (0xf<<2) | (3<<7), 1,
                                      "SYNCHRONIZE CACHE");
                if (reply == 0)
                        reply = do_synchronize_cache(common);
                break;

        case TEST_UNIT_READY:
                common->data_size_from_cmnd = 0;
                reply = check_command(common, 6, DATA_DIR_NONE,
                                0, 1,
                                "TEST UNIT READY");
                break;

        /*
         * Although optional, this command is used by MS-Windows.  We
         * support a minimal version: BytChk must be 0.
         */
        case VERIFY:
                common->data_size_from_cmnd = 0;
                reply = check_command(common, 10, DATA_DIR_NONE,
                                      (1<<1) | (0xf<<2) | (3<<7), 1,
                                      "VERIFY");
                if (reply == 0)
                        reply = do_verify(common);
                break;

        case WRITE_6:
                i = common->cmnd[4];
                common->data_size_from_cmnd = (i == 0) ? 256 : i;
                reply = check_command_size_in_blocks(common, 6,
                                      DATA_DIR_FROM_HOST,
                                      (7<<1) | (1<<4), 1,

                                      "WRITE(6)");
                if (reply == 0)
                        reply = do_write(common);
                break;

        case WRITE_10:
                common->data_size_from_cmnd =
                                get_unaligned_be16(&common->cmnd[7]);
                reply = check_command_size_in_blocks(common, 10,
                                      DATA_DIR_FROM_HOST,
                                      (1<<1) | (0xf<<2) | (3<<7), 1,
                                      "WRITE(10)");
                if (reply == 0)
                        reply = do_write(common);
                break;

        case WRITE_12:
                common->data_size_from_cmnd =
                                get_unaligned_be32(&common->cmnd[6]);
                reply = check_command_size_in_blocks(common, 12,
                                      DATA_DIR_FROM_HOST,
                                      (1<<1) | (0xf<<2) | (0xf<<6), 1,
                                      "WRITE(12)");
                if (reply == 0)
                        reply = do_write(common);
                break;

        /*
         * Some mandatory commands that we recognize but don't implement.
         * They don't mean much in this setting.  It's left as an exercise
         * for anyone interested to implement RESERVE and RELEASE in terms
         * of Posix locks.
         */
        case FORMAT_UNIT:
        case RELEASE:
        case RESERVE:
        case SEND_DIAGNOSTIC:
                /* Fall through */

        default:
unknown_cmnd:
                common->data_size_from_cmnd = 0;
                sprintf(unknown, "Unknown x%02x", common->cmnd[0]);
                reply = check_command(common, common->cmnd_size,
                                      DATA_DIR_UNKNOWN, ~0, 0, unknown);
                if (reply == 0) {
                        common->curlun->sense_data = SS_INVALID_COMMAND;
                        reply = -EINVAL;
                }
                break;
        }
        up_read(&common->filesem);

        if (reply == -EINTR || signal_pending(current))
                return -EINTR;

        /* Set up the single reply buffer for finish_reply() */
        if (reply == -EINVAL)
                reply = 0;              /* Error reply length */
        if (reply >= 0 && common->data_dir == DATA_DIR_TO_HOST) {
                reply = min((u32)reply, common->data_size_from_cmnd);
                bh->inreq->length = reply;
                bh->state = BUF_STATE_FULL;
                common->residue -= reply;
        }                               /* Otherwise it's already set */

        return 0;
}


/*-------------------------------------------------------------------------*/

static int received_cbw(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct usb_request      *req = bh->outreq;
        struct bulk_cb_wrap     *cbw = req->buf;
        struct fsg_common       *common = fsg->common;

        /* Was this a real packet?  Should it be ignored? */
        if (req->status || test_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags))
                return -EINVAL;

        /* Is the CBW valid? */
        if (req->actual != US_BULK_CB_WRAP_LEN ||
                        cbw->Signature != cpu_to_le32(
                                US_BULK_CB_SIGN)) {
                DBG(fsg, "invalid CBW: len %u sig 0x%x\n",
                                req->actual,
                                le32_to_cpu(cbw->Signature));

                /*
                 * The Bulk-only spec says we MUST stall the IN endpoint
                 * (6.6.1), so it's unavoidable.  It also says we must
                 * retain this state until the next reset, but there's
                 * no way to tell the controller driver it should ignore
                 * Clear-Feature(HALT) requests.
                 *
                 * We aren't required to halt the OUT endpoint; instead
                 * we can simply accept and discard any data received
                 * until the next reset.
                 */
                wedge_bulk_in_endpoint(fsg);
                set_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);
                return -EINVAL;
        }

        /* Is the CBW meaningful? */
        if (cbw->Lun >= ARRAY_SIZE(common->luns) ||
            cbw->Flags & ~US_BULK_FLAG_IN || cbw->Length <= 0 ||
            cbw->Length > MAX_COMMAND_SIZE) {
                DBG(fsg, "non-meaningful CBW: lun = %u, flags = 0x%x, "
                                "cmdlen %u\n",
                                cbw->Lun, cbw->Flags, cbw->Length);

                /*
                 * We can do anything we want here, so let's stall the
                 * bulk pipes if we are allowed to.
                 */
                if (common->can_stall) {
                        fsg_set_halt(fsg, fsg->bulk_out);
                        halt_bulk_in_endpoint(fsg);
                }
                return -EINVAL;
        }

        /* Save the command for later */
        common->cmnd_size = cbw->Length;
        memcpy(common->cmnd, cbw->CDB, common->cmnd_size);
        if (cbw->Flags & US_BULK_FLAG_IN)
                common->data_dir = DATA_DIR_TO_HOST;
        else
                common->data_dir = DATA_DIR_FROM_HOST;
        common->data_size = le32_to_cpu(cbw->DataTransferLength);
        if (common->data_size == 0)
                common->data_dir = DATA_DIR_NONE;
        common->lun = cbw->Lun;
        if (common->lun < ARRAY_SIZE(common->luns))
                common->curlun = common->luns[common->lun];
        else
                common->curlun = NULL;
        common->tag = cbw->Tag;
        return 0;
}

static int get_next_command(struct fsg_common *common)
{
        struct fsg_buffhd       *bh;
        int                     rc = 0;

        /* Wait for the next buffer to become available */
        bh = common->next_buffhd_to_fill;
        rc = sleep_thread(common, true, bh);
        if (rc)
                return rc;

        /* Queue a request to read a Bulk-only CBW */
        set_bulk_out_req_length(common, bh, US_BULK_CB_WRAP_LEN);
        if (!start_out_transfer(common, bh))
                /* Don't know what to do if common->fsg is NULL */
                return -EIO;

        /*
         * We will drain the buffer in software, which means we
         * can reuse it for the next filling.  No need to advance
         * next_buffhd_to_fill.
         */

        /* Wait for the CBW to arrive */
        rc = sleep_thread(common, true, bh);
        if (rc)
                return rc;

        rc = fsg_is_set(common) ? received_cbw(common->fsg, bh) : -EIO;
        bh->state = BUF_STATE_EMPTY;

        return rc;
}


/*-------------------------------------------------------------------------*/

static int alloc_request(struct fsg_common *common, struct usb_ep *ep,
                struct usb_request **preq)
{
        *preq = usb_ep_alloc_request(ep, GFP_ATOMIC);
        if (*preq)
                return 0;
        ERROR(common, "can't allocate request for %s\n", ep->name);
        return -ENOMEM;
}

/* Reset interface setting and re-init endpoint state (toggle etc). */
static int do_set_interface(struct fsg_common *common, struct fsg_dev *new_fsg)
{
        struct fsg_dev *fsg;
        int i, rc = 0;

        if (common->running)
                DBG(common, "reset interface\n");

reset:
        /* Deallocate the requests */
        if (common->fsg) {
                fsg = common->fsg;

                for (i = 0; i < common->fsg_num_buffers; ++i) {
                        struct fsg_buffhd *bh = &common->buffhds[i];

                        if (bh->inreq) {
                                usb_ep_free_request(fsg->bulk_in, bh->inreq);
                                bh->inreq = NULL;
                        }
                        if (bh->outreq) {
                                usb_ep_free_request(fsg->bulk_out, bh->outreq);
                                bh->outreq = NULL;
                        }
                }

                /* Disable the endpoints */
                if (fsg->bulk_in_enabled) {
                        usb_ep_disable(fsg->bulk_in);
                        fsg->bulk_in_enabled = 0;
                }
                if (fsg->bulk_out_enabled) {
                        usb_ep_disable(fsg->bulk_out);
                        fsg->bulk_out_enabled = 0;
                }

                common->fsg = NULL;
                wake_up(&common->fsg_wait);
        }

        common->running = 0;
        if (!new_fsg || rc)
                return rc;

        common->fsg = new_fsg;
        fsg = common->fsg;

        /* Enable the endpoints */
        rc = config_ep_by_speed(common->gadget, &(fsg->function), fsg->bulk_in);
        if (rc)
                goto reset;
        rc = usb_ep_enable(fsg->bulk_in);
        if (rc)
                goto reset;
        fsg->bulk_in->driver_data = common;
        fsg->bulk_in_enabled = 1;

        rc = config_ep_by_speed(common->gadget, &(fsg->function),
                                fsg->bulk_out);
        if (rc)
                goto reset;
        rc = usb_ep_enable(fsg->bulk_out);
        if (rc)
                goto reset;
        fsg->bulk_out->driver_data = common;
        fsg->bulk_out_enabled = 1;
        common->bulk_out_maxpacket = usb_endpoint_maxp(fsg->bulk_out->desc);
        clear_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);

        /* Allocate the requests */
        for (i = 0; i < common->fsg_num_buffers; ++i) {
                struct fsg_buffhd       *bh = &common->buffhds[i];

                rc = alloc_request(common, fsg->bulk_in, &bh->inreq);
                if (rc)
                        goto reset;
                rc = alloc_request(common, fsg->bulk_out, &bh->outreq);
                if (rc)
                        goto reset;
                bh->inreq->buf = bh->outreq->buf = bh->buf;
                bh->inreq->context = bh->outreq->context = bh;
                bh->inreq->complete = bulk_in_complete;
                bh->outreq->complete = bulk_out_complete;
        }

        common->running = 1;
        for (i = 0; i < ARRAY_SIZE(common->luns); ++i)
                if (common->luns[i])
                        common->luns[i]->unit_attention_data =
                                SS_RESET_OCCURRED;
        return rc;
}


/****************************** ALT CONFIGS ******************************/

static int fsg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
        struct fsg_dev *fsg = fsg_from_func(f);
        fsg->common->new_fsg = fsg;
        raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE);
        return USB_GADGET_DELAYED_STATUS;
}

static void fsg_disable(struct usb_function *f)
{
        struct fsg_dev *fsg = fsg_from_func(f);
        fsg->common->new_fsg = NULL;
        raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE);
}


/*-------------------------------------------------------------------------*/

static void handle_exception(struct fsg_common *common)
{
        int                     i;
        struct fsg_buffhd       *bh;
        enum fsg_state          old_state;
        struct fsg_lun          *curlun;
        unsigned int            exception_req_tag;

        /*
         * Clear the existing signals.  Anything but SIGUSR1 is converted
         * into a high-priority EXIT exception.
         */
        for (;;) {
                int sig = kernel_dequeue_signal(NULL);
                if (!sig)
                        break;
                if (sig != SIGUSR1) {
                        spin_lock_irq(&common->lock);
                        if (common->state < FSG_STATE_EXIT)
                                DBG(common, "Main thread exiting on signal\n");
                        common->state = FSG_STATE_EXIT;
                        spin_unlock_irq(&common->lock);
                }
        }

        /* Cancel all the pending transfers */
        if (likely(common->fsg)) {
                for (i = 0; i < common->fsg_num_buffers; ++i) {
                        bh = &common->buffhds[i];
                        if (bh->state == BUF_STATE_SENDING)
                                usb_ep_dequeue(common->fsg->bulk_in, bh->inreq);
                        if (bh->state == BUF_STATE_RECEIVING)
                                usb_ep_dequeue(common->fsg->bulk_out,
                                               bh->outreq);

                        /* Wait for a transfer to become idle */
                        if (sleep_thread(common, false, bh))
                                return;
                }

                /* Clear out the controller's fifos */
                if (common->fsg->bulk_in_enabled)
                        usb_ep_fifo_flush(common->fsg->bulk_in);
                if (common->fsg->bulk_out_enabled)
                        usb_ep_fifo_flush(common->fsg->bulk_out);
        }

        /*
         * Reset the I/O buffer states and pointers, the SCSI
         * state, and the exception.  Then invoke the handler.
         */
        spin_lock_irq(&common->lock);

        for (i = 0; i < common->fsg_num_buffers; ++i) {
                bh = &common->buffhds[i];
                bh->state = BUF_STATE_EMPTY;
        }
        common->next_buffhd_to_fill = &common->buffhds[0];
        common->next_buffhd_to_drain = &common->buffhds[0];
        exception_req_tag = common->exception_req_tag;
        old_state = common->state;
        common->state = FSG_STATE_NORMAL;

        if (old_state != FSG_STATE_ABORT_BULK_OUT) {
                for (i = 0; i < ARRAY_SIZE(common->luns); ++i) {
                        curlun = common->luns[i];
                        if (!curlun)
                                continue;
                        curlun->prevent_medium_removal = 0;
                        curlun->sense_data = SS_NO_SENSE;
                        curlun->unit_attention_data = SS_NO_SENSE;
                        curlun->sense_data_info = 0;
                        curlun->info_valid = 0;
                }
        }
        spin_unlock_irq(&common->lock);

        /* Carry out any extra actions required for the exception */
        switch (old_state) {
        case FSG_STATE_NORMAL:
                break;

        case FSG_STATE_ABORT_BULK_OUT:
                send_status(common);
                break;

        case FSG_STATE_PROTOCOL_RESET:
                /*
                 * In case we were forced against our will to halt a
                 * bulk endpoint, clear the halt now.  (The SuperH UDC
                 * requires this.)
                 */
                if (!fsg_is_set(common))
                        break;
                if (test_and_clear_bit(IGNORE_BULK_OUT,
                                       &common->fsg->atomic_bitflags))
                        usb_ep_clear_halt(common->fsg->bulk_in);

                if (common->ep0_req_tag == exception_req_tag)
                        ep0_queue(common);      /* Complete the status stage */

                /*
                 * Technically this should go here, but it would only be
                 * a waste of time.  Ditto for the INTERFACE_CHANGE and
                 * CONFIG_CHANGE cases.
                 */
                /* for (i = 0; i < common->ARRAY_SIZE(common->luns); ++i) */
                /*      if (common->luns[i]) */
                /*              common->luns[i]->unit_attention_data = */
                /*                      SS_RESET_OCCURRED;  */
                break;

        case FSG_STATE_CONFIG_CHANGE:
                do_set_interface(common, common->new_fsg);
                if (common->new_fsg)
                        usb_composite_setup_continue(common->cdev);
                break;

        case FSG_STATE_EXIT:
                do_set_interface(common, NULL);         /* Free resources */
                spin_lock_irq(&common->lock);
                common->state = FSG_STATE_TERMINATED;   /* Stop the thread */
                spin_unlock_irq(&common->lock);
                break;

        case FSG_STATE_TERMINATED:
                break;
        }
}


/*-------------------------------------------------------------------------*/

static int fsg_main_thread(void *common_)
{
        struct fsg_common       *common = common_;

        /*
         * Allow the thread to be killed by a signal, but set the signal mask
         * to block everything but INT, TERM, KILL, and USR1.
         */
        allow_signal(SIGINT);
        allow_signal(SIGTERM);
        allow_signal(SIGKILL);
        allow_signal(SIGUSR1);

        /* Allow the thread to be frozen */
        set_freezable();

        /*
         * Arrange for userspace references to be interpreted as kernel
         * pointers.  That way we can pass a kernel pointer to a routine
         * that expects a __user pointer and it will work okay.
         */
        set_fs(get_ds());

        /* The main loop */
        while (common->state != FSG_STATE_TERMINATED) {
                if (exception_in_progress(common) || signal_pending(current)) {
                        handle_exception(common);
                        continue;
                }

                if (!common->running) {
                        sleep_thread(common, true, NULL);
                        continue;
                }

                if (get_next_command(common) || exception_in_progress(common))
                        continue;
                if (do_scsi_command(common) || exception_in_progress(common))
                        continue;
                if (finish_reply(common) || exception_in_progress(common))
                        continue;
                send_status(common);
        }

        spin_lock_irq(&common->lock);
        common->thread_task = NULL;
        spin_unlock_irq(&common->lock);

        if (!common->ops || !common->ops->thread_exits
         || common->ops->thread_exits(common) < 0) {
                int i;

                down_write(&common->filesem);
                for (i = 0; i < ARRAY_SIZE(common->luns); i++) {
                        struct fsg_lun *curlun = common->luns[i];
                        if (!curlun || !fsg_lun_is_open(curlun))
                                continue;

                        fsg_lun_close(curlun);
                        curlun->unit_attention_data = SS_MEDIUM_NOT_PRESENT;
                }
                up_write(&common->filesem);
        }

        /* Let fsg_unbind() know the thread has exited */
        complete_and_exit(&common->thread_notifier, 0);
}


/*************************** DEVICE ATTRIBUTES ***************************/

static ssize_t ro_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct fsg_lun          *curlun = fsg_lun_from_dev(dev);

        return fsg_show_ro(curlun, buf);
}

static ssize_t nofua_show(struct device *dev, struct device_attribute *attr,
                          char *buf)
{
        struct fsg_lun          *curlun = fsg_lun_from_dev(dev);

        return fsg_show_nofua(curlun, buf);
}

static ssize_t file_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct fsg_lun          *curlun = fsg_lun_from_dev(dev);
        struct rw_semaphore     *filesem = dev_get_drvdata(dev);

        return fsg_show_file(curlun, filesem, buf);
}

static ssize_t ro_store(struct device *dev, struct device_attribute *attr,
                        const char *buf, size_t count)
{
        struct fsg_lun          *curlun = fsg_lun_from_dev(dev);
        struct rw_semaphore     *filesem = dev_get_drvdata(dev);

        return fsg_store_ro(curlun, filesem, buf, count);
}

static ssize_t nofua_store(struct device *dev, struct device_attribute *attr,
                           const char *buf, size_t count)
{
        struct fsg_lun          *curlun = fsg_lun_from_dev(dev);

        return fsg_store_nofua(curlun, buf, count);
}

static ssize_t file_store(struct device *dev, struct device_attribute *attr,
                          const char *buf, size_t count)
{
        struct fsg_lun          *curlun = fsg_lun_from_dev(dev);
        struct rw_semaphore     *filesem = dev_get_drvdata(dev);

        return fsg_store_file(curlun, filesem, buf, count);
}

static DEVICE_ATTR_RW(nofua);
/* mode wil be set in fsg_lun_attr_is_visible() */
static DEVICE_ATTR(ro, 0, ro_show, ro_store);
static DEVICE_ATTR(file, 0, file_show, file_store);

/****************************** FSG COMMON ******************************/

static void fsg_common_release(struct kref *ref);

static void fsg_lun_release(struct device *dev)
{
        /* Nothing needs to be done */
}

void fsg_common_get(struct fsg_common *common)
{
        kref_get(&common->ref);
}
EXPORT_SYMBOL_GPL(fsg_common_get);

void fsg_common_put(struct fsg_common *common)
{
        kref_put(&common->ref, fsg_common_release);
}
EXPORT_SYMBOL_GPL(fsg_common_put);

static struct fsg_common *fsg_common_setup(struct fsg_common *common)
{
        if (!common) {
                common = kzalloc(sizeof(*common), GFP_KERNEL);
                if (!common)
                        return ERR_PTR(-ENOMEM);
                common->free_storage_on_release = 1;
        } else {
                common->free_storage_on_release = 0;
        }
        init_rwsem(&common->filesem);
        spin_lock_init(&common->lock);
        kref_init(&common->ref);
        init_completion(&common->thread_notifier);
        init_waitqueue_head(&common->io_wait);
        init_waitqueue_head(&common->fsg_wait);
        common->state = FSG_STATE_TERMINATED;
        memset(common->luns, 0, sizeof(common->luns));

        return common;
}

void fsg_common_set_sysfs(struct fsg_common *common, bool sysfs)
{
        common->sysfs = sysfs;
}
EXPORT_SYMBOL_GPL(fsg_common_set_sysfs);

static void _fsg_common_free_buffers(struct fsg_buffhd *buffhds, unsigned n)
{
        if (buffhds) {
                struct fsg_buffhd *bh = buffhds;
                while (n--) {
                        kfree(bh->buf);
                        ++bh;
                }
                kfree(buffhds);
        }
}

int fsg_common_set_num_buffers(struct fsg_common *common, unsigned int n)
{
        struct fsg_buffhd *bh, *buffhds;
        int i;

        buffhds = kcalloc(n, sizeof(*buffhds), GFP_KERNEL);
        if (!buffhds)
                return -ENOMEM;

        /* Data buffers cyclic list */
        bh = buffhds;
        i = n;
        goto buffhds_first_it;
        do {
                bh->next = bh + 1;
                ++bh;
buffhds_first_it:
                bh->buf = kmalloc(FSG_BUFLEN, GFP_KERNEL);
                if (unlikely(!bh->buf))
                        goto error_release;
        } while (--i);
        bh->next = buffhds;

        _fsg_common_free_buffers(common->buffhds, common->fsg_num_buffers);
        common->fsg_num_buffers = n;
        common->buffhds = buffhds;

        return 0;

error_release:
        /*
         * "buf"s pointed to by heads after n - i are NULL
         * so releasing them won't hurt
         */
        _fsg_common_free_buffers(buffhds, n);

        return -ENOMEM;
}
EXPORT_SYMBOL_GPL(fsg_common_set_num_buffers);

void fsg_common_remove_lun(struct fsg_lun *lun)
{
        if (device_is_registered(&lun->dev))
                device_unregister(&lun->dev);
        fsg_lun_close(lun);
        kfree(lun);
}
EXPORT_SYMBOL_GPL(fsg_common_remove_lun);

static void _fsg_common_remove_luns(struct fsg_common *common, int n)
{
        int i;

        for (i = 0; i < n; ++i)
                if (common->luns[i]) {
                        fsg_common_remove_lun(common->luns[i]);
                        common->luns[i] = NULL;
                }
}

void fsg_common_remove_luns(struct fsg_common *common)
{
        _fsg_common_remove_luns(common, ARRAY_SIZE(common->luns));
}
EXPORT_SYMBOL_GPL(fsg_common_remove_luns);

void fsg_common_set_ops(struct fsg_common *common,
                        const struct fsg_operations *ops)
{
        common->ops = ops;
}
EXPORT_SYMBOL_GPL(fsg_common_set_ops);

void fsg_common_free_buffers(struct fsg_common *common)
{
        _fsg_common_free_buffers(common->buffhds, common->fsg_num_buffers);
        common->buffhds = NULL;
}
EXPORT_SYMBOL_GPL(fsg_common_free_buffers);

int fsg_common_set_cdev(struct fsg_common *common,
                         struct usb_composite_dev *cdev, bool can_stall)
{
        struct usb_string *us;

        common->gadget = cdev->gadget;
        common->ep0 = cdev->gadget->ep0;
        common->ep0req = cdev->req;
        common->cdev = cdev;

        us = usb_gstrings_attach(cdev, fsg_strings_array,
                                 ARRAY_SIZE(fsg_strings));
        if (IS_ERR(us))
                return PTR_ERR(us);

        fsg_intf_desc.iInterface = us[FSG_STRING_INTERFACE].id;

        /*
         * Some peripheral controllers are known not to be able to
         * halt bulk endpoints correctly.  If one of them is present,
         * disable stalls.
         */
        common->can_stall = can_stall &&
                        gadget_is_stall_supported(common->gadget);

        return 0;
}
EXPORT_SYMBOL_GPL(fsg_common_set_cdev);

static struct attribute *fsg_lun_dev_attrs[] = {
        &dev_attr_ro.attr,
        &dev_attr_file.attr,
        &dev_attr_nofua.attr,
        NULL
};

static umode_t fsg_lun_dev_is_visible(struct kobject *kobj,
                                      struct attribute *attr, int idx)
{
        struct device *dev = kobj_to_dev(kobj);
        struct fsg_lun *lun = fsg_lun_from_dev(dev);

        if (attr == &dev_attr_ro.attr)
                return lun->cdrom ? S_IRUGO : (S_IWUSR | S_IRUGO);
        if (attr == &dev_attr_file.attr)
                return lun->removable ? (S_IWUSR | S_IRUGO) : S_IRUGO;
        return attr->mode;
}

static const struct attribute_group fsg_lun_dev_group = {
        .attrs = fsg_lun_dev_attrs,
        .is_visible = fsg_lun_dev_is_visible,
};

static const struct attribute_group *fsg_lun_dev_groups[] = {
        &fsg_lun_dev_group,
        NULL
};

int fsg_common_create_lun(struct fsg_common *common, struct fsg_lun_config *cfg,
                          unsigned int id, const char *name,
                          const char **name_pfx)
{
        struct fsg_lun *lun;
        char *pathbuf, *p;
        int rc = -ENOMEM;

        if (id >= ARRAY_SIZE(common->luns))
                return -ENODEV;

        if (common->luns[id])
                return -EBUSY;

        if (!cfg->filename && !cfg->removable) {
                pr_err("no file given for LUN%d\n", id);
                return -EINVAL;
        }

        lun = kzalloc(sizeof(*lun), GFP_KERNEL);
        if (!lun)
                return -ENOMEM;

        lun->name_pfx = name_pfx;

        lun->cdrom = !!cfg->cdrom;
        lun->ro = cfg->cdrom || cfg->ro;
        lun->initially_ro = lun->ro;
        lun->removable = !!cfg->removable;

        if (!common->sysfs) {
                /* we DON'T own the name!*/
                lun->name = name;
        } else {
                lun->dev.release = fsg_lun_release;
                lun->dev.parent = &common->gadget->dev;
                lun->dev.groups = fsg_lun_dev_groups;
                dev_set_drvdata(&lun->dev, &common->filesem);
                dev_set_name(&lun->dev, "%s", name);
                lun->name = dev_name(&lun->dev);

                rc = device_register(&lun->dev);
                if (rc) {
                        pr_info("failed to register LUN%d: %d\n", id, rc);
                        put_device(&lun->dev);
                        goto error_sysfs;
                }
        }

        common->luns[id] = lun;

        if (cfg->filename) {
                rc = fsg_lun_open(lun, cfg->filename);
                if (rc)
                        goto error_lun;
        }

        pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
        p = "(no medium)";
        if (fsg_lun_is_open(lun)) {
                p = "(error)";
                if (pathbuf) {
                        p = file_path(lun->filp, pathbuf, PATH_MAX);
                        if (IS_ERR(p))
                                p = "(error)";
                }
        }
        pr_info("LUN: %s%s%sfile: %s\n",
              lun->removable ? "removable " : "",
              lun->ro ? "read only " : "",
              lun->cdrom ? "CD-ROM " : "",
              p);
        kfree(pathbuf);

        return 0;

error_lun:
        if (device_is_registered(&lun->dev))
                device_unregister(&lun->dev);
        fsg_lun_close(lun);
        common->luns[id] = NULL;
error_sysfs:
        kfree(lun);
        return rc;
}
EXPORT_SYMBOL_GPL(fsg_common_create_lun);

int fsg_common_create_luns(struct fsg_common *common, struct fsg_config *cfg)
{
        char buf[8]; /* enough for 100000000 different numbers, decimal */
        int i, rc;

        fsg_common_remove_luns(common);

        for (i = 0; i < cfg->nluns; ++i) {
                snprintf(buf, sizeof(buf), "lun%d", i);
                rc = fsg_common_create_lun(common, &cfg->luns[i], i, buf, NULL);
                if (rc)
                        goto fail;
        }

        pr_info("Number of LUNs=%d\n", cfg->nluns);

        return 0;

fail:
        _fsg_common_remove_luns(common, i);
        return rc;
}
EXPORT_SYMBOL_GPL(fsg_common_create_luns);

void fsg_common_set_inquiry_string(struct fsg_common *common, const char *vn,
                                   const char *pn)
{
        int i;

        /* Prepare inquiryString */
        i = get_default_bcdDevice();
        snprintf(common->inquiry_string, sizeof(common->inquiry_string),
                 "%-8s%-16s%04x", vn ?: "Linux",
                 /* Assume product name dependent on the first LUN */
                 pn ?: ((*common->luns)->cdrom
                     ? "File-CD Gadget"
                     : "File-Stor Gadget"),
                 i);
}
EXPORT_SYMBOL_GPL(fsg_common_set_inquiry_string);

static void fsg_common_release(struct kref *ref)
{
        struct fsg_common *common = container_of(ref, struct fsg_common, ref);
        int i;

        /* If the thread isn't already dead, tell it to exit now */
        if (common->state != FSG_STATE_TERMINATED) {
                raise_exception(common, FSG_STATE_EXIT);
                wait_for_completion(&common->thread_notifier);
        }

        for (i = 0; i < ARRAY_SIZE(common->luns); ++i) {
                struct fsg_lun *lun = common->luns[i];
                if (!lun)
                        continue;
                fsg_lun_close(lun);
                if (device_is_registered(&lun->dev))
                        device_unregister(&lun->dev);
                kfree(lun);
        }

        _fsg_common_free_buffers(common->buffhds, common->fsg_num_buffers);
        if (common->free_storage_on_release)
                kfree(common);
}


/*-------------------------------------------------------------------------*/

static int fsg_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct fsg_dev          *fsg = fsg_from_func(f);
        struct fsg_common       *common = fsg->common;
        struct usb_gadget       *gadget = c->cdev->gadget;
        int                     i;
        struct usb_ep           *ep;
        unsigned                max_burst;
        int                     ret;
        struct fsg_opts         *opts;

        /* Don't allow to bind if we don't have at least one LUN */
        ret = _fsg_common_get_max_lun(common);
        if (ret < 0) {
                pr_err("There should be at least one LUN.\n");
                return -EINVAL;
        }

        opts = fsg_opts_from_func_inst(f->fi);
        if (!opts->no_configfs) {
                ret = fsg_common_set_cdev(fsg->common, c->cdev,
                                          fsg->common->can_stall);
                if (ret)
                        return ret;
                fsg_common_set_inquiry_string(fsg->common, NULL, NULL);
        }

        if (!common->thread_task) {
                common->state = FSG_STATE_NORMAL;
                common->thread_task =
                        kthread_create(fsg_main_thread, common, "file-storage");
                if (IS_ERR(common->thread_task)) {
                        ret = PTR_ERR(common->thread_task);
                        common->thread_task = NULL;
                        common->state = FSG_STATE_TERMINATED;
                        return ret;
                }
                DBG(common, "I/O thread pid: %d\n",
                    task_pid_nr(common->thread_task));
                wake_up_process(common->thread_task);
        }

        fsg->gadget = gadget;

        /* New interface */
        i = usb_interface_id(c, f);
        if (i < 0)
                goto fail;
        fsg_intf_desc.bInterfaceNumber = i;
        fsg->interface_number = i;

        /* Find all the endpoints we will use */
        ep = usb_ep_autoconfig(gadget, &fsg_fs_bulk_in_desc);
        if (!ep)
                goto autoconf_fail;
        fsg->bulk_in = ep;

        ep = usb_ep_autoconfig(gadget, &fsg_fs_bulk_out_desc);
        if (!ep)
                goto autoconf_fail;
        fsg->bulk_out = ep;

        /* Assume endpoint addresses are the same for both speeds */
        fsg_hs_bulk_in_desc.bEndpointAddress =
                fsg_fs_bulk_in_desc.bEndpointAddress;
        fsg_hs_bulk_out_desc.bEndpointAddress =
                fsg_fs_bulk_out_desc.bEndpointAddress;

        /* Calculate bMaxBurst, we know packet size is 1024 */
        max_burst = min_t(unsigned, FSG_BUFLEN / 1024, 15);

        fsg_ss_bulk_in_desc.bEndpointAddress =
                fsg_fs_bulk_in_desc.bEndpointAddress;
        fsg_ss_bulk_in_comp_desc.bMaxBurst = max_burst;

        fsg_ss_bulk_out_desc.bEndpointAddress =
                fsg_fs_bulk_out_desc.bEndpointAddress;
        fsg_ss_bulk_out_comp_desc.bMaxBurst = max_burst;

        ret = usb_assign_descriptors(f, fsg_fs_function, fsg_hs_function,
                        fsg_ss_function, fsg_ss_function);
        if (ret)
                goto autoconf_fail;

        return 0;

autoconf_fail:
        ERROR(fsg, "unable to autoconfigure all endpoints\n");
        i = -ENOTSUPP;
fail:
        /* terminate the thread */
        if (fsg->common->state != FSG_STATE_TERMINATED) {
                raise_exception(fsg->common, FSG_STATE_EXIT);
                wait_for_completion(&fsg->common->thread_notifier);
        }
        return i;
}

/****************************** ALLOCATE FUNCTION *************************/

static void fsg_unbind(struct usb_configuration *c, struct usb_function *f)
{
        struct fsg_dev          *fsg = fsg_from_func(f);
        struct fsg_common       *common = fsg->common;

        DBG(fsg, "unbind\n");
        if (fsg->common->fsg == fsg) {
                fsg->common->new_fsg = NULL;
                raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE);
                /* FIXME: make interruptible or killable somehow? */
                wait_event(common->fsg_wait, common->fsg != fsg);
        }

        usb_free_all_descriptors(&fsg->function);
}

static inline struct fsg_lun_opts *to_fsg_lun_opts(struct config_item *item)
{
        return container_of(to_config_group(item), struct fsg_lun_opts, group);
}

static inline struct fsg_opts *to_fsg_opts(struct config_item *item)
{
        return container_of(to_config_group(item), struct fsg_opts,
                            func_inst.group);
}

static void fsg_lun_attr_release(struct config_item *item)
{
        struct fsg_lun_opts *lun_opts;

        lun_opts = to_fsg_lun_opts(item);
        kfree(lun_opts);
}

static struct configfs_item_operations fsg_lun_item_ops = {
        .release                = fsg_lun_attr_release,
};

static ssize_t fsg_lun_opts_file_show(struct config_item *item, char *page)
{
        struct fsg_lun_opts *opts = to_fsg_lun_opts(item);
        struct fsg_opts *fsg_opts = to_fsg_opts(opts->group.cg_item.ci_parent);

        return fsg_show_file(opts->lun, &fsg_opts->common->filesem, page);
}

static ssize_t fsg_lun_opts_file_store(struct config_item *item,
                                       const char *page, size_t len)
{
        struct fsg_lun_opts *opts = to_fsg_lun_opts(item);
        struct fsg_opts *fsg_opts = to_fsg_opts(opts->group.cg_item.ci_parent);

        return fsg_store_file(opts->lun, &fsg_opts->common->filesem, page, len);
}

CONFIGFS_ATTR(fsg_lun_opts_, file);

static ssize_t fsg_lun_opts_ro_show(struct config_item *item, char *page)
{
        return fsg_show_ro(to_fsg_lun_opts(item)->lun, page);
}

static ssize_t fsg_lun_opts_ro_store(struct config_item *item,
                                       const char *page, size_t len)
{
        struct fsg_lun_opts *opts = to_fsg_lun_opts(item);
        struct fsg_opts *fsg_opts = to_fsg_opts(opts->group.cg_item.ci_parent);

        return fsg_store_ro(opts->lun, &fsg_opts->common->filesem, page, len);
}

CONFIGFS_ATTR(fsg_lun_opts_, ro);

static ssize_t fsg_lun_opts_removable_show(struct config_item *item,
                                           char *page)
{
        return fsg_show_removable(to_fsg_lun_opts(item)->lun, page);
}

static ssize_t fsg_lun_opts_removable_store(struct config_item *item,
                                       const char *page, size_t len)
{
        return fsg_store_removable(to_fsg_lun_opts(item)->lun, page, len);
}

CONFIGFS_ATTR(fsg_lun_opts_, removable);

static ssize_t fsg_lun_opts_cdrom_show(struct config_item *item, char *page)
{
        return fsg_show_cdrom(to_fsg_lun_opts(item)->lun, page);
}

static ssize_t fsg_lun_opts_cdrom_store(struct config_item *item,
                                       const char *page, size_t len)
{
        struct fsg_lun_opts *opts = to_fsg_lun_opts(item);
        struct fsg_opts *fsg_opts = to_fsg_opts(opts->group.cg_item.ci_parent);

        return fsg_store_cdrom(opts->lun, &fsg_opts->common->filesem, page,
                               len);
}

CONFIGFS_ATTR(fsg_lun_opts_, cdrom);

static ssize_t fsg_lun_opts_nofua_show(struct config_item *item, char *page)
{
        return fsg_show_nofua(to_fsg_lun_opts(item)->lun, page);
}

static ssize_t fsg_lun_opts_nofua_store(struct config_item *item,
                                       const char *page, size_t len)
{
        return fsg_store_nofua(to_fsg_lun_opts(item)->lun, page, len);
}

CONFIGFS_ATTR(fsg_lun_opts_, nofua);

static ssize_t fsg_lun_opts_inquiry_string_show(struct config_item *item,
                                                char *page)
{
        return fsg_show_inquiry_string(to_fsg_lun_opts(item)->lun, page);
}

static ssize_t fsg_lun_opts_inquiry_string_store(struct config_item *item,
                                                 const char *page, size_t len)
{
        return fsg_store_inquiry_string(to_fsg_lun_opts(item)->lun, page, len);
}

CONFIGFS_ATTR(fsg_lun_opts_, inquiry_string);

static struct configfs_attribute *fsg_lun_attrs[] = {
        &fsg_lun_opts_attr_file,
        &fsg_lun_opts_attr_ro,
        &fsg_lun_opts_attr_removable,
        &fsg_lun_opts_attr_cdrom,
        &fsg_lun_opts_attr_nofua,
        &fsg_lun_opts_attr_inquiry_string,
        NULL,
};

static struct config_item_type fsg_lun_type = {
        .ct_item_ops    = &fsg_lun_item_ops,
        .ct_attrs       = fsg_lun_attrs,
        .ct_owner       = THIS_MODULE,
};

static struct config_group *fsg_lun_make(struct config_group *group,
                                         const char *name)
{
        struct fsg_lun_opts *opts;
        struct fsg_opts *fsg_opts;
        struct fsg_lun_config config;
        char *num_str;
        u8 num;
        int ret;

        num_str = strchr(name, '.');
        if (!num_str) {
                pr_err("Unable to locate . in LUN.NUMBER\n");
                return ERR_PTR(-EINVAL);
        }
        num_str++;

        ret = kstrtou8(num_str, 0, &num);
        if (ret)
                return ERR_PTR(ret);

        fsg_opts = to_fsg_opts(&group->cg_item);
        if (num >= FSG_MAX_LUNS)
                return ERR_PTR(-ERANGE);

        mutex_lock(&fsg_opts->lock);
        if (fsg_opts->refcnt || fsg_opts->common->luns[num]) {
                ret = -EBUSY;
                goto out;
        }

        opts = kzalloc(sizeof(*opts), GFP_KERNEL);
        if (!opts) {
                ret = -ENOMEM;
                goto out;
        }

        memset(&config, 0, sizeof(config));
        config.removable = true;

        ret = fsg_common_create_lun(fsg_opts->common, &config, num, name,
                                    (const char **)&group->cg_item.ci_name);
        if (ret) {
                kfree(opts);
                goto out;
        }
        opts->lun = fsg_opts->common->luns[num];
        opts->lun_id = num;
        mutex_unlock(&fsg_opts->lock);

        config_group_init_type_name(&opts->group, name, &fsg_lun_type);

        return &opts->group;
out:
        mutex_unlock(&fsg_opts->lock);
        return ERR_PTR(ret);
}

static void fsg_lun_drop(struct config_group *group, struct config_item *item)
{
        struct fsg_lun_opts *lun_opts;
        struct fsg_opts *fsg_opts;

        lun_opts = to_fsg_lun_opts(item);
        fsg_opts = to_fsg_opts(&group->cg_item);

        mutex_lock(&fsg_opts->lock);
        if (fsg_opts->refcnt) {
                struct config_item *gadget;

                gadget = group->cg_item.ci_parent->ci_parent;
                unregister_gadget_item(gadget);
        }

        fsg_common_remove_lun(lun_opts->lun);
        fsg_opts->common->luns[lun_opts->lun_id] = NULL;
        lun_opts->lun_id = 0;
        mutex_unlock(&fsg_opts->lock);

        config_item_put(item);
}

static void fsg_attr_release(struct config_item *item)
{
        struct fsg_opts *opts = to_fsg_opts(item);

        usb_put_function_instance(&opts->func_inst);
}

static struct configfs_item_operations fsg_item_ops = {
        .release                = fsg_attr_release,
};

static ssize_t fsg_opts_stall_show(struct config_item *item, char *page)
{
        struct fsg_opts *opts = to_fsg_opts(item);
        int result;

        mutex_lock(&opts->lock);
        result = sprintf(page, "%d", opts->common->can_stall);
        mutex_unlock(&opts->lock);

        return result;
}

static ssize_t fsg_opts_stall_store(struct config_item *item, const char *page,
                                    size_t len)
{
        struct fsg_opts *opts = to_fsg_opts(item);
        int ret;
        bool stall;

        mutex_lock(&opts->lock);

        if (opts->refcnt) {
                mutex_unlock(&opts->lock);
                return -EBUSY;
        }

        ret = strtobool(page, &stall);
        if (!ret) {
                opts->common->can_stall = stall;
                ret = len;
        }

        mutex_unlock(&opts->lock);

        return ret;
}

CONFIGFS_ATTR(fsg_opts_, stall);

#ifdef CONFIG_USB_GADGET_DEBUG_FILES
static ssize_t fsg_opts_num_buffers_show(struct config_item *item, char *page)
{
        struct fsg_opts *opts = to_fsg_opts(item);
        int result;

        mutex_lock(&opts->lock);
        result = sprintf(page, "%d", opts->common->fsg_num_buffers);
        mutex_unlock(&opts->lock);

        return result;
}

static ssize_t fsg_opts_num_buffers_store(struct config_item *item,
                                          const char *page, size_t len)
{
        struct fsg_opts *opts = to_fsg_opts(item);
        int ret;
        u8 num;

        mutex_lock(&opts->lock);
        if (opts->refcnt) {
                ret = -EBUSY;
                goto end;
        }
        ret = kstrtou8(page, 0, &num);
        if (ret)
                goto end;

        fsg_common_set_num_buffers(opts->common, num);
        ret = len;

end:
        mutex_unlock(&opts->lock);
        return ret;
}

CONFIGFS_ATTR(fsg_opts_, num_buffers);
#endif

static struct configfs_attribute *fsg_attrs[] = {
        &fsg_opts_attr_stall,
#ifdef CONFIG_USB_GADGET_DEBUG_FILES
        &fsg_opts_attr_num_buffers,
#endif
        NULL,
};

static struct configfs_group_operations fsg_group_ops = {
        .make_group     = fsg_lun_make,
        .drop_item      = fsg_lun_drop,
};

static struct config_item_type fsg_func_type = {
        .ct_item_ops    = &fsg_item_ops,
        .ct_group_ops   = &fsg_group_ops,
        .ct_attrs       = fsg_attrs,
        .ct_owner       = THIS_MODULE,
};

static void fsg_free_inst(struct usb_function_instance *fi)
{
        struct fsg_opts *opts;

        opts = fsg_opts_from_func_inst(fi);
        fsg_common_put(opts->common);
        kfree(opts);
}

static struct usb_function_instance *fsg_alloc_inst(void)
{
        struct fsg_opts *opts;
        struct fsg_lun_config config;
        int rc;

        opts = kzalloc(sizeof(*opts), GFP_KERNEL);
        if (!opts)
                return ERR_PTR(-ENOMEM);
        mutex_init(&opts->lock);
        opts->func_inst.free_func_inst = fsg_free_inst;
        opts->common = fsg_common_setup(opts->common);
        if (IS_ERR(opts->common)) {
                rc = PTR_ERR(opts->common);
                goto release_opts;
        }

        rc = fsg_common_set_num_buffers(opts->common,
                                        CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS);
        if (rc)
                goto release_opts;

        pr_info(FSG_DRIVER_DESC ", version: " FSG_DRIVER_VERSION "\n");

        memset(&config, 0, sizeof(config));
        config.removable = true;
        rc = fsg_common_create_lun(opts->common, &config, 0, "lun.0",
                        (const char **)&opts->func_inst.group.cg_item.ci_name);
        if (rc)
                goto release_buffers;

        opts->lun0.lun = opts->common->luns[0];
        opts->lun0.lun_id = 0;

        config_group_init_type_name(&opts->func_inst.group, "", &fsg_func_type);

        config_group_init_type_name(&opts->lun0.group, "lun.0", &fsg_lun_type);
        configfs_add_default_group(&opts->lun0.group, &opts->func_inst.group);

        return &opts->func_inst;

release_buffers:
        fsg_common_free_buffers(opts->common);
release_opts:
        kfree(opts);
        return ERR_PTR(rc);
}

static void fsg_free(struct usb_function *f)
{
        struct fsg_dev *fsg;
        struct fsg_opts *opts;

        fsg = container_of(f, struct fsg_dev, function);
        opts = container_of(f->fi, struct fsg_opts, func_inst);

        mutex_lock(&opts->lock);
        opts->refcnt--;
        mutex_unlock(&opts->lock);

        kfree(fsg);
}

static struct usb_function *fsg_alloc(struct usb_function_instance *fi)
{
        struct fsg_opts *opts = fsg_opts_from_func_inst(fi);
        struct fsg_common *common = opts->common;
        struct fsg_dev *fsg;

        fsg = kzalloc(sizeof(*fsg), GFP_KERNEL);
        if (unlikely(!fsg))
                return ERR_PTR(-ENOMEM);

        mutex_lock(&opts->lock);
        opts->refcnt++;
        mutex_unlock(&opts->lock);

        fsg->function.name      = FSG_DRIVER_DESC;
        fsg->function.bind      = fsg_bind;
        fsg->function.unbind    = fsg_unbind;
        fsg->function.setup     = fsg_setup;
        fsg->function.set_alt   = fsg_set_alt;
        fsg->function.disable   = fsg_disable;
        fsg->function.free_func = fsg_free;

        fsg->common               = common;

        return &fsg->function;
}

DECLARE_USB_FUNCTION_INIT(mass_storage, fsg_alloc_inst, fsg_alloc);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Michal Nazarewicz");

/************************* Module parameters *************************/


void fsg_config_from_params(struct fsg_config *cfg,
                       const struct fsg_module_parameters *params,
                       unsigned int fsg_num_buffers)
{
        struct fsg_lun_config *lun;
        unsigned i;

        /* Configure LUNs */
        cfg->nluns =
                min(params->luns ?: (params->file_count ?: 1u),
                    (unsigned)FSG_MAX_LUNS);
        for (i = 0, lun = cfg->luns; i < cfg->nluns; ++i, ++lun) {
                lun->ro = !!params->ro[i];
                lun->cdrom = !!params->cdrom[i];
                lun->removable = !!params->removable[i];
                lun->filename =
                        params->file_count > i && params->file[i][0]
                        ? params->file[i]
                        : NULL;
        }

        /* Let MSF use defaults */
        cfg->vendor_name = NULL;
        cfg->product_name = NULL;

        cfg->ops = NULL;
        cfg->private_data = NULL;

        /* Finalise */
        cfg->can_stall = params->stall;
        cfg->fsg_num_buffers = fsg_num_buffers;
}
EXPORT_SYMBOL_GPL(fsg_config_from_params);