// SPDX-License-Identifier: GPL-2.0
/*
 * USB Attached SCSI
 * Note that this is not the same as the USB Mass Storage driver
 *
 * Copyright Hans de Goede <hdegoede@redhat.com> for Red Hat, Inc. 2013 - 2016
 * Copyright Matthew Wilcox for Intel Corp, 2010
 * Copyright Sarah Sharp for Intel Corp, 2010
 */

#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/usb_usual.h>
#include <linux/usb/hcd.h>
#include <linux/usb/storage.h>
#include <linux/usb/uas.h>

#include <scsi/scsi.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_dbg.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_tcq.h>

#include "uas-detect.h"
#include "scsiglue.h"

#define MAX_CMNDS 256

struct uas_dev_info {
        struct usb_interface *intf;
        struct usb_device *udev;
        struct usb_anchor cmd_urbs;
        struct usb_anchor sense_urbs;
        struct usb_anchor data_urbs;
        unsigned long flags;
        int qdepth, resetting;
        unsigned cmd_pipe, status_pipe, data_in_pipe, data_out_pipe;
        unsigned use_streams:1;
        unsigned shutdown:1;
        struct scsi_cmnd *cmnd[MAX_CMNDS];
        spinlock_t lock;
        struct work_struct work;
        struct work_struct scan_work;      /* for async scanning */
};

enum {
        SUBMIT_STATUS_URB       = BIT(1),
        ALLOC_DATA_IN_URB       = BIT(2),
        SUBMIT_DATA_IN_URB      = BIT(3),
        ALLOC_DATA_OUT_URB      = BIT(4),
        SUBMIT_DATA_OUT_URB     = BIT(5),
        ALLOC_CMD_URB           = BIT(6),
        SUBMIT_CMD_URB          = BIT(7),
        COMMAND_INFLIGHT        = BIT(8),
        DATA_IN_URB_INFLIGHT    = BIT(9),
        DATA_OUT_URB_INFLIGHT   = BIT(10),
        COMMAND_ABORTED         = BIT(11),
        IS_IN_WORK_LIST         = BIT(12),
};

/* Overrides scsi_pointer */
struct uas_cmd_info {
        unsigned int state;
        unsigned int uas_tag;
        struct urb *cmd_urb;
        struct urb *data_in_urb;
        struct urb *data_out_urb;
};

/* I hate forward declarations, but I actually have a loop */
static int uas_submit_urbs(struct scsi_cmnd *cmnd,
                                struct uas_dev_info *devinfo);
static void uas_do_work(struct work_struct *work);
static int uas_try_complete(struct scsi_cmnd *cmnd, const char *caller);
static void uas_free_streams(struct uas_dev_info *devinfo);
static void uas_log_cmd_state(struct scsi_cmnd *cmnd, const char *prefix,
                                int status);

/*
 * This driver needs its own workqueue, as we need to control memory allocation.
 *
 * In the course of error handling and power management uas_wait_for_pending_cmnds()
 * needs to flush pending work items. In these contexts we cannot allocate memory
 * by doing block IO as we would deadlock. For the same reason we cannot wait
 * for anything allocating memory not heeding these constraints.
 *
 * So we have to control all work items that can be on the workqueue we flush.
 * Hence we cannot share a queue and need our own.
 */
static struct workqueue_struct *workqueue;

static void uas_do_work(struct work_struct *work)
{
        struct uas_dev_info *devinfo =
                container_of(work, struct uas_dev_info, work);
        struct uas_cmd_info *cmdinfo;
        struct scsi_cmnd *cmnd;
        unsigned long flags;
        int i, err;

        spin_lock_irqsave(&devinfo->lock, flags);

        if (devinfo->resetting)
                goto out;

        for (i = 0; i < devinfo->qdepth; i++) {
                if (!devinfo->cmnd[i])
                        continue;

                cmnd = devinfo->cmnd[i];
                cmdinfo = (void *)&cmnd->SCp;

                if (!(cmdinfo->state & IS_IN_WORK_LIST))
                        continue;

                err = uas_submit_urbs(cmnd, cmnd->device->hostdata);
                if (!err)
                        cmdinfo->state &= ~IS_IN_WORK_LIST;
                else
                        queue_work(workqueue, &devinfo->work);
        }
out:
        spin_unlock_irqrestore(&devinfo->lock, flags);
}

static void uas_scan_work(struct work_struct *work)
{
        struct uas_dev_info *devinfo =
                container_of(work, struct uas_dev_info, scan_work);
        struct Scsi_Host *shost = usb_get_intfdata(devinfo->intf);

        dev_dbg(&devinfo->intf->dev, "starting scan\n");
        scsi_scan_host(shost);
        dev_dbg(&devinfo->intf->dev, "scan complete\n");
}

static void uas_add_work(struct uas_cmd_info *cmdinfo)
{
        struct scsi_pointer *scp = (void *)cmdinfo;
        struct scsi_cmnd *cmnd = container_of(scp, struct scsi_cmnd, SCp);
        struct uas_dev_info *devinfo = cmnd->device->hostdata;

        lockdep_assert_held(&devinfo->lock);
        cmdinfo->state |= IS_IN_WORK_LIST;
        queue_work(workqueue, &devinfo->work);
}

static void uas_zap_pending(struct uas_dev_info *devinfo, int result)
{
        struct uas_cmd_info *cmdinfo;
        struct scsi_cmnd *cmnd;
        unsigned long flags;
        int i, err;

        spin_lock_irqsave(&devinfo->lock, flags);
        for (i = 0; i < devinfo->qdepth; i++) {
                if (!devinfo->cmnd[i])
                        continue;

                cmnd = devinfo->cmnd[i];
                cmdinfo = (void *)&cmnd->SCp;
                uas_log_cmd_state(cmnd, __func__, 0);
                /* Sense urbs were killed, clear COMMAND_INFLIGHT manually */
                cmdinfo->state &= ~COMMAND_INFLIGHT;
                cmnd->result = result << 16;
                err = uas_try_complete(cmnd, __func__);
                WARN_ON(err != 0);
        }
        spin_unlock_irqrestore(&devinfo->lock, flags);
}

static void uas_sense(struct urb *urb, struct scsi_cmnd *cmnd)
{
        struct sense_iu *sense_iu = urb->transfer_buffer;
        struct scsi_device *sdev = cmnd->device;

        if (urb->actual_length > 16) {
                unsigned len = be16_to_cpup(&sense_iu->len);
                if (len + 16 != urb->actual_length) {
                        int newlen = min(len + 16, urb->actual_length) - 16;
                        if (newlen < 0)
                                newlen = 0;
                        sdev_printk(KERN_INFO, sdev, "%s: urb length %d "
                                "disagrees with IU sense data length %d, "
                                "using %d bytes of sense data\n", __func__,
                                        urb->actual_length, len, newlen);
                        len = newlen;
                }
                memcpy(cmnd->sense_buffer, sense_iu->sense, len);
        }

        cmnd->result = sense_iu->status;
}

static void uas_log_cmd_state(struct scsi_cmnd *cmnd, const char *prefix,
                              int status)
{
        struct uas_cmd_info *ci = (void *)&cmnd->SCp;
        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;

        if (status == -ENODEV) /* too late */
                return;

        scmd_printk(KERN_INFO, cmnd,
                    "%s %d uas-tag %d inflight:%s%s%s%s%s%s%s%s%s%s%s%s ",
                    prefix, status, cmdinfo->uas_tag,
                    (ci->state & SUBMIT_STATUS_URB)     ? " s-st"  : "",
                    (ci->state & ALLOC_DATA_IN_URB)     ? " a-in"  : "",
                    (ci->state & SUBMIT_DATA_IN_URB)    ? " s-in"  : "",
                    (ci->state & ALLOC_DATA_OUT_URB)    ? " a-out" : "",
                    (ci->state & SUBMIT_DATA_OUT_URB)   ? " s-out" : "",
                    (ci->state & ALLOC_CMD_URB)         ? " a-cmd" : "",
                    (ci->state & SUBMIT_CMD_URB)        ? " s-cmd" : "",
                    (ci->state & COMMAND_INFLIGHT)      ? " CMD"   : "",
                    (ci->state & DATA_IN_URB_INFLIGHT)  ? " IN"    : "",
                    (ci->state & DATA_OUT_URB_INFLIGHT) ? " OUT"   : "",
                    (ci->state & COMMAND_ABORTED)       ? " abort" : "",
                    (ci->state & IS_IN_WORK_LIST)       ? " work"  : "");
        scsi_print_command(cmnd);
}

static void uas_free_unsubmitted_urbs(struct scsi_cmnd *cmnd)
{
        struct uas_cmd_info *cmdinfo;

        if (!cmnd)
                return;

        cmdinfo = (void *)&cmnd->SCp;

        if (cmdinfo->state & SUBMIT_CMD_URB)
                usb_free_urb(cmdinfo->cmd_urb);

        /* data urbs may have never gotten their submit flag set */
        if (!(cmdinfo->state & DATA_IN_URB_INFLIGHT))
                usb_free_urb(cmdinfo->data_in_urb);
        if (!(cmdinfo->state & DATA_OUT_URB_INFLIGHT))
                usb_free_urb(cmdinfo->data_out_urb);
}

static int uas_try_complete(struct scsi_cmnd *cmnd, const char *caller)
{
        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
        struct uas_dev_info *devinfo = (void *)cmnd->device->hostdata;

        lockdep_assert_held(&devinfo->lock);
        if (cmdinfo->state & (COMMAND_INFLIGHT |
                              DATA_IN_URB_INFLIGHT |
                              DATA_OUT_URB_INFLIGHT |
                              COMMAND_ABORTED))
                return -EBUSY;
        devinfo->cmnd[cmdinfo->uas_tag - 1] = NULL;
        uas_free_unsubmitted_urbs(cmnd);
        cmnd->scsi_done(cmnd);
        return 0;
}

static void uas_xfer_data(struct urb *urb, struct scsi_cmnd *cmnd,
                          unsigned direction)
{
        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
        int err;

        cmdinfo->state |= direction | SUBMIT_STATUS_URB;
        err = uas_submit_urbs(cmnd, cmnd->device->hostdata);
        if (err) {
                uas_add_work(cmdinfo);
        }
}

static bool uas_evaluate_response_iu(struct response_iu *riu, struct scsi_cmnd *cmnd)
{
        u8 response_code = riu->response_code;

        switch (response_code) {
        case RC_INCORRECT_LUN:
                cmnd->result = DID_BAD_TARGET << 16;
                break;
        case RC_TMF_SUCCEEDED:
                cmnd->result = DID_OK << 16;
                break;
        case RC_TMF_NOT_SUPPORTED:
                cmnd->result = DID_TARGET_FAILURE << 16;
                break;
        default:
                uas_log_cmd_state(cmnd, "response iu", response_code);
                cmnd->result = DID_ERROR << 16;
                break;
        }

        return response_code == RC_TMF_SUCCEEDED;
}

static void uas_stat_cmplt(struct urb *urb)
{
        struct iu *iu = urb->transfer_buffer;
        struct Scsi_Host *shost = urb->context;
        struct uas_dev_info *devinfo = (struct uas_dev_info *)shost->hostdata;
        struct urb *data_in_urb = NULL;
        struct urb *data_out_urb = NULL;
        struct scsi_cmnd *cmnd;
        struct uas_cmd_info *cmdinfo;
        unsigned long flags;
        unsigned int idx;
        int status = urb->status;
        bool success;

        spin_lock_irqsave(&devinfo->lock, flags);

        if (devinfo->resetting)
                goto out;

        if (status) {
                if (status != -ENOENT && status != -ECONNRESET && status != -ESHUTDOWN)
                        dev_err(&urb->dev->dev, "stat urb: status %d\n", status);
                goto out;
        }

        idx = be16_to_cpup(&iu->tag) - 1;
        if (idx >= MAX_CMNDS || !devinfo->cmnd[idx]) {
                dev_err(&urb->dev->dev,
                        "stat urb: no pending cmd for uas-tag %d\n", idx + 1);
                goto out;
        }

        cmnd = devinfo->cmnd[idx];
        cmdinfo = (void *)&cmnd->SCp;

        if (!(cmdinfo->state & COMMAND_INFLIGHT)) {
                uas_log_cmd_state(cmnd, "unexpected status cmplt", 0);
                goto out;
        }

        switch (iu->iu_id) {
        case IU_ID_STATUS:
                uas_sense(urb, cmnd);
                if (cmnd->result != 0) {
                        /* cancel data transfers on error */
                        data_in_urb = usb_get_urb(cmdinfo->data_in_urb);
                        data_out_urb = usb_get_urb(cmdinfo->data_out_urb);
                }
                cmdinfo->state &= ~COMMAND_INFLIGHT;
                uas_try_complete(cmnd, __func__);
                break;
        case IU_ID_READ_READY:
                if (!cmdinfo->data_in_urb ||
                                (cmdinfo->state & DATA_IN_URB_INFLIGHT)) {
                        uas_log_cmd_state(cmnd, "unexpected read rdy", 0);
                        break;
                }
                uas_xfer_data(urb, cmnd, SUBMIT_DATA_IN_URB);
                break;
        case IU_ID_WRITE_READY:
                if (!cmdinfo->data_out_urb ||
                                (cmdinfo->state & DATA_OUT_URB_INFLIGHT)) {
                        uas_log_cmd_state(cmnd, "unexpected write rdy", 0);
                        break;
                }
                uas_xfer_data(urb, cmnd, SUBMIT_DATA_OUT_URB);
                break;
        case IU_ID_RESPONSE:
                cmdinfo->state &= ~COMMAND_INFLIGHT;
                success = uas_evaluate_response_iu((struct response_iu *)iu, cmnd);
                if (!success) {
                        /* Error, cancel data transfers */
                        data_in_urb = usb_get_urb(cmdinfo->data_in_urb);
                        data_out_urb = usb_get_urb(cmdinfo->data_out_urb);
                }
                uas_try_complete(cmnd, __func__);
                break;
        default:
                uas_log_cmd_state(cmnd, "bogus IU", iu->iu_id);
        }
out:
        usb_free_urb(urb);
        spin_unlock_irqrestore(&devinfo->lock, flags);

        /* Unlinking of data urbs must be done without holding the lock */
        if (data_in_urb) {
                usb_unlink_urb(data_in_urb);
                usb_put_urb(data_in_urb);
        }
        if (data_out_urb) {
                usb_unlink_urb(data_out_urb);
                usb_put_urb(data_out_urb);
        }
}

static void uas_data_cmplt(struct urb *urb)
{
        struct scsi_cmnd *cmnd = urb->context;
        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
        struct uas_dev_info *devinfo = (void *)cmnd->device->hostdata;
        struct scsi_data_buffer *sdb = &cmnd->sdb;
        unsigned long flags;
        int status = urb->status;

        spin_lock_irqsave(&devinfo->lock, flags);

        if (cmdinfo->data_in_urb == urb) {
                cmdinfo->state &= ~DATA_IN_URB_INFLIGHT;
                cmdinfo->data_in_urb = NULL;
        } else if (cmdinfo->data_out_urb == urb) {
                cmdinfo->state &= ~DATA_OUT_URB_INFLIGHT;
                cmdinfo->data_out_urb = NULL;
        }

        if (devinfo->resetting)
                goto out;

        /* Data urbs should not complete before the cmd urb is submitted */
        if (cmdinfo->state & SUBMIT_CMD_URB) {
                uas_log_cmd_state(cmnd, "unexpected data cmplt", 0);
                goto out;
        }

        if (status) {
                if (status != -ENOENT && status != -ECONNRESET && status != -ESHUTDOWN)
                        uas_log_cmd_state(cmnd, "data cmplt err", status);
                /* error: no data transfered */
                scsi_set_resid(cmnd, sdb->length);
        } else {
                scsi_set_resid(cmnd, sdb->length - urb->actual_length);
        }
        uas_try_complete(cmnd, __func__);
out:
        usb_free_urb(urb);
        spin_unlock_irqrestore(&devinfo->lock, flags);
}

static void uas_cmd_cmplt(struct urb *urb)
{
        if (urb->status)
                dev_err(&urb->dev->dev, "cmd cmplt err %d\n", urb->status);

        usb_free_urb(urb);
}

static struct urb *uas_alloc_data_urb(struct uas_dev_info *devinfo, gfp_t gfp,
                                      struct scsi_cmnd *cmnd,
                                      enum dma_data_direction dir)
{
        struct usb_device *udev = devinfo->udev;
        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
        struct urb *urb = usb_alloc_urb(0, gfp);
        struct scsi_data_buffer *sdb = &cmnd->sdb;
        unsigned int pipe = (dir == DMA_FROM_DEVICE)
                ? devinfo->data_in_pipe : devinfo->data_out_pipe;

        if (!urb)
                goto out;
        usb_fill_bulk_urb(urb, udev, pipe, NULL, sdb->length,
                          uas_data_cmplt, cmnd);
        if (devinfo->use_streams)
                urb->stream_id = cmdinfo->uas_tag;
        urb->num_sgs = udev->bus->sg_tablesize ? sdb->table.nents : 0;
        urb->sg = sdb->table.sgl;
 out:
        return urb;
}

static struct urb *uas_alloc_sense_urb(struct uas_dev_info *devinfo, gfp_t gfp,
                                       struct scsi_cmnd *cmnd)
{
        struct usb_device *udev = devinfo->udev;
        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
        struct urb *urb = usb_alloc_urb(0, gfp);
        struct sense_iu *iu;

        if (!urb)
                goto out;

        iu = kzalloc(sizeof(*iu), gfp);
        if (!iu)
                goto free;

        usb_fill_bulk_urb(urb, udev, devinfo->status_pipe, iu, sizeof(*iu),
                          uas_stat_cmplt, cmnd->device->host);
        if (devinfo->use_streams)
                urb->stream_id = cmdinfo->uas_tag;
        urb->transfer_flags |= URB_FREE_BUFFER;
 out:
        return urb;
 free:
        usb_free_urb(urb);
        return NULL;
}

static struct urb *uas_alloc_cmd_urb(struct uas_dev_info *devinfo, gfp_t gfp,
                                        struct scsi_cmnd *cmnd)
{
        struct usb_device *udev = devinfo->udev;
        struct scsi_device *sdev = cmnd->device;
        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
        struct urb *urb = usb_alloc_urb(0, gfp);
        struct command_iu *iu;
        int len;

        if (!urb)
                goto out;

        len = cmnd->cmd_len - 16;
        if (len < 0)
                len = 0;
        len = ALIGN(len, 4);
        iu = kzalloc(sizeof(*iu) + len, gfp);
        if (!iu)
                goto free;

        iu->iu_id = IU_ID_COMMAND;
        iu->tag = cpu_to_be16(cmdinfo->uas_tag);
        iu->prio_attr = UAS_SIMPLE_TAG;
        iu->len = len;
        int_to_scsilun(sdev->lun, &iu->lun);
        memcpy(iu->cdb, cmnd->cmnd, cmnd->cmd_len);

        usb_fill_bulk_urb(urb, udev, devinfo->cmd_pipe, iu, sizeof(*iu) + len,
                                                        uas_cmd_cmplt, NULL);
        urb->transfer_flags |= URB_FREE_BUFFER;
 out:
        return urb;
 free:
        usb_free_urb(urb);
        return NULL;
}

/*
 * Why should I request the Status IU before sending the Command IU?  Spec
 * says to, but also says the device may receive them in any order.  Seems
 * daft to me.
 */

static struct urb *uas_submit_sense_urb(struct scsi_cmnd *cmnd, gfp_t gfp)
{
        struct uas_dev_info *devinfo = cmnd->device->hostdata;
        struct urb *urb;
        int err;

        urb = uas_alloc_sense_urb(devinfo, gfp, cmnd);
        if (!urb)
                return NULL;
        usb_anchor_urb(urb, &devinfo->sense_urbs);
        err = usb_submit_urb(urb, gfp);
        if (err) {
                usb_unanchor_urb(urb);
                uas_log_cmd_state(cmnd, "sense submit err", err);
                usb_free_urb(urb);
                return NULL;
        }
        return urb;
}

static int uas_submit_urbs(struct scsi_cmnd *cmnd,
                           struct uas_dev_info *devinfo)
{
        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
        struct urb *urb;
        int err;

        lockdep_assert_held(&devinfo->lock);
        if (cmdinfo->state & SUBMIT_STATUS_URB) {
                urb = uas_submit_sense_urb(cmnd, GFP_ATOMIC);
                if (!urb)
                        return SCSI_MLQUEUE_DEVICE_BUSY;
                cmdinfo->state &= ~SUBMIT_STATUS_URB;
        }

        if (cmdinfo->state & ALLOC_DATA_IN_URB) {
                cmdinfo->data_in_urb = uas_alloc_data_urb(devinfo, GFP_ATOMIC,
                                                        cmnd, DMA_FROM_DEVICE);
                if (!cmdinfo->data_in_urb)
                        return SCSI_MLQUEUE_DEVICE_BUSY;
                cmdinfo->state &= ~ALLOC_DATA_IN_URB;
        }

        if (cmdinfo->state & SUBMIT_DATA_IN_URB) {
                usb_anchor_urb(cmdinfo->data_in_urb, &devinfo->data_urbs);
                err = usb_submit_urb(cmdinfo->data_in_urb, GFP_ATOMIC);
                if (err) {
                        usb_unanchor_urb(cmdinfo->data_in_urb);
                        uas_log_cmd_state(cmnd, "data in submit err", err);
                        return SCSI_MLQUEUE_DEVICE_BUSY;
                }
                cmdinfo->state &= ~SUBMIT_DATA_IN_URB;
                cmdinfo->state |= DATA_IN_URB_INFLIGHT;
        }

        if (cmdinfo->state & ALLOC_DATA_OUT_URB) {
                cmdinfo->data_out_urb = uas_alloc_data_urb(devinfo, GFP_ATOMIC,
                                                        cmnd, DMA_TO_DEVICE);
                if (!cmdinfo->data_out_urb)
                        return SCSI_MLQUEUE_DEVICE_BUSY;
                cmdinfo->state &= ~ALLOC_DATA_OUT_URB;
        }

        if (cmdinfo->state & SUBMIT_DATA_OUT_URB) {
                usb_anchor_urb(cmdinfo->data_out_urb, &devinfo->data_urbs);
                err = usb_submit_urb(cmdinfo->data_out_urb, GFP_ATOMIC);
                if (err) {
                        usb_unanchor_urb(cmdinfo->data_out_urb);
                        uas_log_cmd_state(cmnd, "data out submit err", err);
                        return SCSI_MLQUEUE_DEVICE_BUSY;
                }
                cmdinfo->state &= ~SUBMIT_DATA_OUT_URB;
                cmdinfo->state |= DATA_OUT_URB_INFLIGHT;
        }

        if (cmdinfo->state & ALLOC_CMD_URB) {
                cmdinfo->cmd_urb = uas_alloc_cmd_urb(devinfo, GFP_ATOMIC, cmnd);
                if (!cmdinfo->cmd_urb)
                        return SCSI_MLQUEUE_DEVICE_BUSY;
                cmdinfo->state &= ~ALLOC_CMD_URB;
        }

        if (cmdinfo->state & SUBMIT_CMD_URB) {
                usb_anchor_urb(cmdinfo->cmd_urb, &devinfo->cmd_urbs);
                err = usb_submit_urb(cmdinfo->cmd_urb, GFP_ATOMIC);
                if (err) {
                        usb_unanchor_urb(cmdinfo->cmd_urb);
                        uas_log_cmd_state(cmnd, "cmd submit err", err);
                        return SCSI_MLQUEUE_DEVICE_BUSY;
                }
                cmdinfo->cmd_urb = NULL;
                cmdinfo->state &= ~SUBMIT_CMD_URB;
                cmdinfo->state |= COMMAND_INFLIGHT;
        }

        return 0;
}

static int uas_queuecommand_lck(struct scsi_cmnd *cmnd,
                                        void (*done)(struct scsi_cmnd *))
{
        struct scsi_device *sdev = cmnd->device;
        struct uas_dev_info *devinfo = sdev->hostdata;
        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
        unsigned long flags;
        int idx, err;

        BUILD_BUG_ON(sizeof(struct uas_cmd_info) > sizeof(struct scsi_pointer));

        /* Re-check scsi_block_requests now that we've the host-lock */
        if (cmnd->device->host->host_self_blocked)
                return SCSI_MLQUEUE_DEVICE_BUSY;

        if ((devinfo->flags & US_FL_NO_ATA_1X) &&
                        (cmnd->cmnd[0] == ATA_12 || cmnd->cmnd[0] == ATA_16)) {
                memcpy(cmnd->sense_buffer, usb_stor_sense_invalidCDB,
                       sizeof(usb_stor_sense_invalidCDB));
                cmnd->result = SAM_STAT_CHECK_CONDITION;
                cmnd->scsi_done(cmnd);
                return 0;
        }

        spin_lock_irqsave(&devinfo->lock, flags);

        if (devinfo->resetting) {
                cmnd->result = DID_ERROR << 16;
                cmnd->scsi_done(cmnd);
                goto zombie;
        }

        /* Find a free uas-tag */
        for (idx = 0; idx < devinfo->qdepth; idx++) {
                if (!devinfo->cmnd[idx])
                        break;
        }
        if (idx == devinfo->qdepth) {
                spin_unlock_irqrestore(&devinfo->lock, flags);
                return SCSI_MLQUEUE_DEVICE_BUSY;
        }

        cmnd->scsi_done = done;

        memset(cmdinfo, 0, sizeof(*cmdinfo));
        cmdinfo->uas_tag = idx + 1; /* uas-tag == usb-stream-id, so 1 based */
        cmdinfo->state = SUBMIT_STATUS_URB | ALLOC_CMD_URB | SUBMIT_CMD_URB;

        switch (cmnd->sc_data_direction) {
        case DMA_FROM_DEVICE:
                cmdinfo->state |= ALLOC_DATA_IN_URB | SUBMIT_DATA_IN_URB;
                break;
        case DMA_BIDIRECTIONAL:
                cmdinfo->state |= ALLOC_DATA_IN_URB | SUBMIT_DATA_IN_URB;
                fallthrough;
        case DMA_TO_DEVICE:
                cmdinfo->state |= ALLOC_DATA_OUT_URB | SUBMIT_DATA_OUT_URB;
        case DMA_NONE:
                break;
        }

        if (!devinfo->use_streams)
                cmdinfo->state &= ~(SUBMIT_DATA_IN_URB | SUBMIT_DATA_OUT_URB);

        err = uas_submit_urbs(cmnd, devinfo);
        /*
         * in case of fatal errors the SCSI layer is peculiar
         * a command that has finished is a success for the purpose
         * of queueing, no matter how fatal the error
         */
        if (err == -ENODEV) {
                cmnd->result = DID_ERROR << 16;
                cmnd->scsi_done(cmnd);
                goto zombie;
        }
        if (err) {
                /* If we did nothing, give up now */
                if (cmdinfo->state & SUBMIT_STATUS_URB) {
                        spin_unlock_irqrestore(&devinfo->lock, flags);
                        return SCSI_MLQUEUE_DEVICE_BUSY;
                }
                uas_add_work(cmdinfo);
        }

        devinfo->cmnd[idx] = cmnd;
zombie:
        spin_unlock_irqrestore(&devinfo->lock, flags);
        return 0;
}

static DEF_SCSI_QCMD(uas_queuecommand)

/*
 * For now we do not support actually sending an abort to the device, so
 * this eh always fails. Still we must define it to make sure that we've
 * dropped all references to the cmnd in question once this function exits.
 */
static int uas_eh_abort_handler(struct scsi_cmnd *cmnd)
{
        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
        struct uas_dev_info *devinfo = (void *)cmnd->device->hostdata;
        struct urb *data_in_urb = NULL;
        struct urb *data_out_urb = NULL;
        unsigned long flags;

        spin_lock_irqsave(&devinfo->lock, flags);

        uas_log_cmd_state(cmnd, __func__, 0);

        /* Ensure that try_complete does not call scsi_done */
        cmdinfo->state |= COMMAND_ABORTED;

        /* Drop all refs to this cmnd, kill data urbs to break their ref */
        devinfo->cmnd[cmdinfo->uas_tag - 1] = NULL;
        if (cmdinfo->state & DATA_IN_URB_INFLIGHT)
                data_in_urb = usb_get_urb(cmdinfo->data_in_urb);
        if (cmdinfo->state & DATA_OUT_URB_INFLIGHT)
                data_out_urb = usb_get_urb(cmdinfo->data_out_urb);

        uas_free_unsubmitted_urbs(cmnd);

        spin_unlock_irqrestore(&devinfo->lock, flags);

        if (data_in_urb) {
                usb_kill_urb(data_in_urb);
                usb_put_urb(data_in_urb);
        }
        if (data_out_urb) {
                usb_kill_urb(data_out_urb);
                usb_put_urb(data_out_urb);
        }

        return FAILED;
}

static int uas_eh_device_reset_handler(struct scsi_cmnd *cmnd)
{
        struct scsi_device *sdev = cmnd->device;
        struct uas_dev_info *devinfo = sdev->hostdata;
        struct usb_device *udev = devinfo->udev;
        unsigned long flags;
        int err;

        err = usb_lock_device_for_reset(udev, devinfo->intf);
        if (err) {
                shost_printk(KERN_ERR, sdev->host,
                             "%s FAILED to get lock err %d\n", __func__, err);
                return FAILED;
        }

        shost_printk(KERN_INFO, sdev->host, "%s start\n", __func__);

        spin_lock_irqsave(&devinfo->lock, flags);
        devinfo->resetting = 1;
        spin_unlock_irqrestore(&devinfo->lock, flags);

        usb_kill_anchored_urbs(&devinfo->cmd_urbs);
        usb_kill_anchored_urbs(&devinfo->sense_urbs);
        usb_kill_anchored_urbs(&devinfo->data_urbs);
        uas_zap_pending(devinfo, DID_RESET);

        err = usb_reset_device(udev);

        spin_lock_irqsave(&devinfo->lock, flags);
        devinfo->resetting = 0;
        spin_unlock_irqrestore(&devinfo->lock, flags);

        usb_unlock_device(udev);

        if (err) {
                shost_printk(KERN_INFO, sdev->host, "%s FAILED err %d\n",
                             __func__, err);
                return FAILED;
        }

        shost_printk(KERN_INFO, sdev->host, "%s success\n", __func__);
        return SUCCESS;
}

static int uas_target_alloc(struct scsi_target *starget)
{
        struct uas_dev_info *devinfo = (struct uas_dev_info *)
                        dev_to_shost(starget->dev.parent)->hostdata;

        if (devinfo->flags & US_FL_NO_REPORT_LUNS)
                starget->no_report_luns = 1;

        return 0;
}

static int uas_slave_alloc(struct scsi_device *sdev)
{
        struct uas_dev_info *devinfo =
                (struct uas_dev_info *)sdev->host->hostdata;

        sdev->hostdata = devinfo;

        /*
         * The protocol has no requirements on alignment in the strict sense.
         * Controllers may or may not have alignment restrictions.
         * As this is not exported, we use an extremely conservative guess.
         */
        blk_queue_update_dma_alignment(sdev->request_queue, (512 - 1));

        if (devinfo->flags & US_FL_MAX_SECTORS_64)
                blk_queue_max_hw_sectors(sdev->request_queue, 64);
        else if (devinfo->flags & US_FL_MAX_SECTORS_240)
                blk_queue_max_hw_sectors(sdev->request_queue, 240);

        return 0;
}

static int uas_slave_configure(struct scsi_device *sdev)
{
        struct uas_dev_info *devinfo = sdev->hostdata;

        if (devinfo->flags & US_FL_NO_REPORT_OPCODES)
                sdev->no_report_opcodes = 1;

        /* A few buggy USB-ATA bridges don't understand FUA */
        if (devinfo->flags & US_FL_BROKEN_FUA)
                sdev->broken_fua = 1;

        /* UAS also needs to support FL_ALWAYS_SYNC */
        if (devinfo->flags & US_FL_ALWAYS_SYNC) {
                sdev->skip_ms_page_3f = 1;
                sdev->skip_ms_page_8 = 1;
                sdev->wce_default_on = 1;
        }

        /* Some disks cannot handle READ_CAPACITY_16 */
        if (devinfo->flags & US_FL_NO_READ_CAPACITY_16)
                sdev->no_read_capacity_16 = 1;

        /*
         * Some disks return the total number of blocks in response
         * to READ CAPACITY rather than the highest block number.
         * If this device makes that mistake, tell the sd driver.
         */
        if (devinfo->flags & US_FL_FIX_CAPACITY)
                sdev->fix_capacity = 1;

        /*
         * in some cases we have to guess
         */
        if (devinfo->flags & US_FL_CAPACITY_HEURISTICS)
                sdev->guess_capacity = 1;

        /*
         * Some devices don't like MODE SENSE with page=0x3f,
         * which is the command used for checking if a device
         * is write-protected.  Now that we tell the sd driver
         * to do a 192-byte transfer with this command the
         * majority of devices work fine, but a few still can't
         * handle it.  The sd driver will simply assume those
         * devices are write-enabled.
         */
        if (devinfo->flags & US_FL_NO_WP_DETECT)
                sdev->skip_ms_page_3f = 1;

        scsi_change_queue_depth(sdev, devinfo->qdepth - 2);
        return 0;
}

static struct scsi_host_template uas_host_template = {
        .module = THIS_MODULE,
        .name = "uas",
        .queuecommand = uas_queuecommand,
        .target_alloc = uas_target_alloc,
        .slave_alloc = uas_slave_alloc,
        .slave_configure = uas_slave_configure,
        .eh_abort_handler = uas_eh_abort_handler,
        .eh_device_reset_handler = uas_eh_device_reset_handler,
        .this_id = -1,
        .skip_settle_delay = 1,
        .dma_boundary = PAGE_SIZE - 1,
};

#define UNUSUAL_DEV(id_vendor, id_product, bcdDeviceMin, bcdDeviceMax, \
                    vendorName, productName, useProtocol, useTransport, \
                    initFunction, flags) \
{ USB_DEVICE_VER(id_vendor, id_product, bcdDeviceMin, bcdDeviceMax), \
        .driver_info = (flags) }

static struct usb_device_id uas_usb_ids[] = {
#       include "unusual_uas.h"
        { USB_INTERFACE_INFO(USB_CLASS_MASS_STORAGE, USB_SC_SCSI, USB_PR_BULK) },
        { USB_INTERFACE_INFO(USB_CLASS_MASS_STORAGE, USB_SC_SCSI, USB_PR_UAS) },
        { }
};
MODULE_DEVICE_TABLE(usb, uas_usb_ids);

#undef UNUSUAL_DEV

static int uas_switch_interface(struct usb_device *udev,
                                struct usb_interface *intf)
{
        struct usb_host_interface *alt;

        alt = uas_find_uas_alt_setting(intf);
        if (!alt)
                return -ENODEV;

        return usb_set_interface(udev, alt->desc.bInterfaceNumber,
                        alt->desc.bAlternateSetting);
}

static int uas_configure_endpoints(struct uas_dev_info *devinfo)
{
        struct usb_host_endpoint *eps[4] = { };
        struct usb_device *udev = devinfo->udev;
        int r;

        r = uas_find_endpoints(devinfo->intf->cur_altsetting, eps);
        if (r)
                return r;

        devinfo->cmd_pipe = usb_sndbulkpipe(udev,
                                            usb_endpoint_num(&eps[0]->desc));
        devinfo->status_pipe = usb_rcvbulkpipe(udev,
                                            usb_endpoint_num(&eps[1]->desc));
        devinfo->data_in_pipe = usb_rcvbulkpipe(udev,
                                            usb_endpoint_num(&eps[2]->desc));
        devinfo->data_out_pipe = usb_sndbulkpipe(udev,
                                            usb_endpoint_num(&eps[3]->desc));

        if (udev->speed < USB_SPEED_SUPER) {
                devinfo->qdepth = 32;
                devinfo->use_streams = 0;
        } else {
                devinfo->qdepth = usb_alloc_streams(devinfo->intf, eps + 1,
                                                    3, MAX_CMNDS, GFP_NOIO);
                if (devinfo->qdepth < 0)
                        return devinfo->qdepth;
                devinfo->use_streams = 1;
        }

        return 0;
}

static void uas_free_streams(struct uas_dev_info *devinfo)
{
        struct usb_device *udev = devinfo->udev;
        struct usb_host_endpoint *eps[3];

        eps[0] = usb_pipe_endpoint(udev, devinfo->status_pipe);
        eps[1] = usb_pipe_endpoint(udev, devinfo->data_in_pipe);
        eps[2] = usb_pipe_endpoint(udev, devinfo->data_out_pipe);
        usb_free_streams(devinfo->intf, eps, 3, GFP_NOIO);
}

static int uas_probe(struct usb_interface *intf, const struct usb_device_id *id)
{
        int result = -ENOMEM;
        struct Scsi_Host *shost = NULL;
        struct uas_dev_info *devinfo;
        struct usb_device *udev = interface_to_usbdev(intf);
        unsigned long dev_flags;

        if (!uas_use_uas_driver(intf, id, &dev_flags))
                return -ENODEV;

        if (uas_switch_interface(udev, intf))
                return -ENODEV;

        shost = scsi_host_alloc(&uas_host_template,
                                sizeof(struct uas_dev_info));
        if (!shost)
                goto set_alt0;

        shost->max_cmd_len = 16 + 252;
        shost->max_id = 1;
        shost->max_lun = 256;
        shost->max_channel = 0;
        shost->sg_tablesize = udev->bus->sg_tablesize;

        devinfo = (struct uas_dev_info *)shost->hostdata;
        devinfo->intf = intf;
        devinfo->udev = udev;
        devinfo->resetting = 0;
        devinfo->shutdown = 0;
        devinfo->flags = dev_flags;
        init_usb_anchor(&devinfo->cmd_urbs);
        init_usb_anchor(&devinfo->sense_urbs);
        init_usb_anchor(&devinfo->data_urbs);
        spin_lock_init(&devinfo->lock);
        INIT_WORK(&devinfo->work, uas_do_work);
        INIT_WORK(&devinfo->scan_work, uas_scan_work);

        result = uas_configure_endpoints(devinfo);
        if (result)
                goto set_alt0;

        /*
         * 1 tag is reserved for untagged commands +
         * 1 tag to avoid off by one errors in some bridge firmwares
         */
        shost->can_queue = devinfo->qdepth - 2;

        usb_set_intfdata(intf, shost);
        result = scsi_add_host(shost, &intf->dev);
        if (result)
                goto free_streams;

        /* Submit the delayed_work for SCSI-device scanning */
        schedule_work(&devinfo->scan_work);

        return result;

free_streams:
        uas_free_streams(devinfo);
        usb_set_intfdata(intf, NULL);
set_alt0:
        usb_set_interface(udev, intf->altsetting[0].desc.bInterfaceNumber, 0);
        if (shost)
                scsi_host_put(shost);
        return result;
}

static int uas_cmnd_list_empty(struct uas_dev_info *devinfo)
{
        unsigned long flags;
        int i, r = 1;

        spin_lock_irqsave(&devinfo->lock, flags);

        for (i = 0; i < devinfo->qdepth; i++) {
                if (devinfo->cmnd[i]) {
                        r = 0; /* Not empty */
                        break;
                }
        }

        spin_unlock_irqrestore(&devinfo->lock, flags);

        return r;
}

/*
 * Wait for any pending cmnds to complete, on usb-2 sense_urbs may temporarily
 * get empty while there still is more work to do due to sense-urbs completing
 * with a READ/WRITE_READY iu code, so keep waiting until the list gets empty.
 */
static int uas_wait_for_pending_cmnds(struct uas_dev_info *devinfo)
{
        unsigned long start_time;
        int r;

        start_time = jiffies;
        do {
                flush_work(&devinfo->work);

                r = usb_wait_anchor_empty_timeout(&devinfo->sense_urbs, 5000);
                if (r == 0)
                        return -ETIME;

                r = usb_wait_anchor_empty_timeout(&devinfo->data_urbs, 500);
                if (r == 0)
                        return -ETIME;

                if (time_after(jiffies, start_time + 5 * HZ))
                        return -ETIME;
        } while (!uas_cmnd_list_empty(devinfo));

        return 0;
}

static int uas_pre_reset(struct usb_interface *intf)
{
        struct Scsi_Host *shost = usb_get_intfdata(intf);
        struct uas_dev_info *devinfo = (struct uas_dev_info *)shost->hostdata;
        unsigned long flags;

        if (devinfo->shutdown)
                return 0;

        /* Block new requests */
        spin_lock_irqsave(shost->host_lock, flags);
        scsi_block_requests(shost);
        spin_unlock_irqrestore(shost->host_lock, flags);

        if (uas_wait_for_pending_cmnds(devinfo) != 0) {
                shost_printk(KERN_ERR, shost, "%s: timed out\n", __func__);
                scsi_unblock_requests(shost);
                return 1;
        }

        uas_free_streams(devinfo);

        return 0;
}

static int uas_post_reset(struct usb_interface *intf)
{
        struct Scsi_Host *shost = usb_get_intfdata(intf);
        struct uas_dev_info *devinfo = (struct uas_dev_info *)shost->hostdata;
        unsigned long flags;
        int err;

        if (devinfo->shutdown)
                return 0;

        err = uas_configure_endpoints(devinfo);
        if (err && err != -ENODEV)
                shost_printk(KERN_ERR, shost,
                             "%s: alloc streams error %d after reset",
                             __func__, err);

        /* we must unblock the host in every case lest we deadlock */
        spin_lock_irqsave(shost->host_lock, flags);
        scsi_report_bus_reset(shost, 0);
        spin_unlock_irqrestore(shost->host_lock, flags);

        scsi_unblock_requests(shost);

        return err ? 1 : 0;
}

static int uas_suspend(struct usb_interface *intf, pm_message_t message)
{
        struct Scsi_Host *shost = usb_get_intfdata(intf);
        struct uas_dev_info *devinfo = (struct uas_dev_info *)shost->hostdata;

        if (uas_wait_for_pending_cmnds(devinfo) != 0) {
                shost_printk(KERN_ERR, shost, "%s: timed out\n", __func__);
                return -ETIME;
        }

        return 0;
}

static int uas_resume(struct usb_interface *intf)
{
        return 0;
}

static int uas_reset_resume(struct usb_interface *intf)
{
        struct Scsi_Host *shost = usb_get_intfdata(intf);
        struct uas_dev_info *devinfo = (struct uas_dev_info *)shost->hostdata;
        unsigned long flags;
        int err;

        err = uas_configure_endpoints(devinfo);
        if (err) {
                shost_printk(KERN_ERR, shost,
                             "%s: alloc streams error %d after reset",
                             __func__, err);
                return -EIO;
        }

        spin_lock_irqsave(shost->host_lock, flags);
        scsi_report_bus_reset(shost, 0);
        spin_unlock_irqrestore(shost->host_lock, flags);

        return 0;
}

static void uas_disconnect(struct usb_interface *intf)
{
        struct Scsi_Host *shost = usb_get_intfdata(intf);
        struct uas_dev_info *devinfo = (struct uas_dev_info *)shost->hostdata;
        unsigned long flags;

        spin_lock_irqsave(&devinfo->lock, flags);
        devinfo->resetting = 1;
        spin_unlock_irqrestore(&devinfo->lock, flags);

        cancel_work_sync(&devinfo->work);
        usb_kill_anchored_urbs(&devinfo->cmd_urbs);
        usb_kill_anchored_urbs(&devinfo->sense_urbs);
        usb_kill_anchored_urbs(&devinfo->data_urbs);
        uas_zap_pending(devinfo, DID_NO_CONNECT);

        /*
         * Prevent SCSI scanning (if it hasn't started yet)
         * or wait for the SCSI-scanning routine to stop.
         */
        cancel_work_sync(&devinfo->scan_work);

        scsi_remove_host(shost);
        uas_free_streams(devinfo);
        scsi_host_put(shost);
}

/*
 * Put the device back in usb-storage mode on shutdown, as some BIOS-es
 * hang on reboot when the device is still in uas mode. Note the reset is
 * necessary as some devices won't revert to usb-storage mode without it.
 */
static void uas_shutdown(struct device *dev)
{
        struct usb_interface *intf = to_usb_interface(dev);
        struct usb_device *udev = interface_to_usbdev(intf);
        struct Scsi_Host *shost = usb_get_intfdata(intf);
        struct uas_dev_info *devinfo = (struct uas_dev_info *)shost->hostdata;

        if (system_state != SYSTEM_RESTART)
                return;

        devinfo->shutdown = 1;
        uas_free_streams(devinfo);
        usb_set_interface(udev, intf->altsetting[0].desc.bInterfaceNumber, 0);
        usb_reset_device(udev);
}

static struct usb_driver uas_driver = {
        .name = "uas",
        .probe = uas_probe,
        .disconnect = uas_disconnect,
        .pre_reset = uas_pre_reset,
        .post_reset = uas_post_reset,
        .suspend = uas_suspend,
        .resume = uas_resume,
        .reset_resume = uas_reset_resume,
        .drvwrap.driver.shutdown = uas_shutdown,
        .id_table = uas_usb_ids,
};

static int __init uas_init(void)
{
        int rv;

        workqueue = alloc_workqueue("uas", WQ_MEM_RECLAIM, 0);
        if (!workqueue)
                return -ENOMEM;

        rv = usb_register(&uas_driver);
        if (rv) {
                destroy_workqueue(workqueue);
                return -ENOMEM;
        }

        return 0;
}

static void __exit uas_exit(void)
{
        usb_deregister(&uas_driver);
        destroy_workqueue(workqueue);
}

module_init(uas_init);
module_exit(uas_exit);

MODULE_LICENSE("GPL");
MODULE_IMPORT_NS(USB_STORAGE);
MODULE_AUTHOR(
        "Hans de Goede <hdegoede@redhat.com>, Matthew Wilcox and Sarah Sharp");