// SPDX-License-Identifier: GPL-2.0
/* Driver for Microtek Scanmaker X6 USB scanner, and possibly others.
 *
 * (C) Copyright 2000 John Fremlin <vii@penguinpowered.com>
 * (C) Copyright 2000 Oliver Neukum <Oliver.Neukum@lrz.uni-muenchen.de>
 *
 * Parts shamelessly stolen from usb-storage and copyright by their
 * authors. Thanks to Matt Dharm for giving us permission!
 *
 * This driver implements a SCSI host controller driver and a USB
 * device driver. To avoid confusion, all the USB related stuff is
 * prefixed by mts_usb_ and all the SCSI stuff by mts_scsi_.
 *
 * Microtek (www.microtek.com) did not release the specifications for
 * their USB protocol to us, so we had to reverse engineer them. We
 * don't know for which models they are valid.
 *
 * The X6 USB has three bulk endpoints, one output (0x1) down which
 * commands and outgoing data are sent, and two input: 0x82 from which
 * normal data is read from the scanner (in packets of maximum 32
 * bytes) and from which the status byte is read, and 0x83 from which
 * the results of a scan (or preview) are read in up to 64 * 1024 byte
 * chunks by the Windows driver. We don't know how much it is possible
 * to read at a time from 0x83.
 *
 * It seems possible to read (with URB transfers) everything from 0x82
 * in one go, without bothering to read in 32 byte chunks.
 *
 * There seems to be an optimisation of a further READ implicit if
 * you simply read from 0x83.
 *
 * Guessed protocol:
 *
 *      Send raw SCSI command to EP 0x1
 *
 *      If there is data to receive:
 *              If the command was READ datatype=image:
 *                      Read a lot of data from EP 0x83
 *              Else:
 *                      Read data from EP 0x82
 *      Else:
 *              If there is data to transmit:
 *                      Write it to EP 0x1
 *
 *      Read status byte from EP 0x82
 *
 * References:
 *
 * The SCSI command set for the scanner is available from
 *      ftp://ftp.microtek.com/microtek/devpack/
 *
 * Microtek NV sent us a more up to date version of the document. If
 * you want it, just send mail.
 *
 * Status:
 *
 *      Untested with multiple scanners.
 *      Untested on SMP.
 *      Untested on a bigendian machine.
 *
 * History:
 *
 *      20000417 starting history
 *      20000417 fixed load oops
 *      20000417 fixed unload oops
 *      20000419 fixed READ IMAGE detection
 *      20000424 started conversion to use URBs
 *      20000502 handled short transfers as errors
 *      20000513 rename and organisation of functions (john)
 *      20000513 added IDs for all products supported by Windows driver (john)
 *      20000514 Rewrote mts_scsi_queuecommand to use URBs (john)
 *      20000514 Version 0.0.8j
 *      20000514 Fix reporting of non-existent devices to SCSI layer (john)
 *      20000514 Added MTS_DEBUG_INT (john)
 *      20000514 Changed "usb-microtek" to "microtek" for consistency (john)
 *      20000514 Stupid bug fixes (john)
 *      20000514 Version 0.0.9j
 *      20000515 Put transfer context and URB in mts_desc (john)
 *      20000515 Added prelim turn off debugging support (john)
 *      20000515 Version 0.0.10j
 *      20000515 Fixed up URB allocation (clear URB on alloc) (john)
 *      20000515 Version 0.0.11j
 *      20000516 Removed unnecessary spinlock in mts_transfer_context (john)
 *      20000516 Removed unnecessary up on instance lock in mts_remove_nolock (john)
 *      20000516 Implemented (badly) scsi_abort (john)
 *      20000516 Version 0.0.12j
 *      20000517 Hopefully removed mts_remove_nolock quasideadlock (john)
 *      20000517 Added mts_debug_dump to print ll USB info (john)
 *      20000518 Tweaks and documentation updates (john)
 *      20000518 Version 0.0.13j
 *      20000518 Cleaned up abort handling (john)
 *      20000523 Removed scsi_command and various scsi_..._resets (john)
 *      20000523 Added unlink URB on scsi_abort, now OHCI supports it (john)
 *      20000523 Fixed last tiresome compile warning (john)
 *      20000523 Version 0.0.14j (though version 0.1 has come out?)
 *      20000602 Added primitive reset
 *      20000602 Version 0.2.0
 *      20000603 various cosmetic changes
 *      20000603 Version 0.2.1
 *      20000620 minor cosmetic changes
 *      20000620 Version 0.2.2
 *      20000822 Hopefully fixed deadlock in mts_remove_nolock()
 *      20000822 Fixed minor race in mts_transfer_cleanup()
 *      20000822 Fixed deadlock on submission error in queuecommand
 *      20000822 Version 0.2.3
 *      20000913 Reduced module size if debugging is off
 *      20000913 Version 0.2.4
 *      20010210 New abort logic
 *      20010210 Version 0.3.0
 *      20010217 Merged scatter/gather
 *      20010218 Version 0.4.0
 *      20010218 Cosmetic fixes
 *      20010218 Version 0.4.1
 *      20010306 Abort while using scatter/gather
 *      20010306 Version 0.4.2
 *      20010311 Remove all timeouts and tidy up generally (john)
 *      20010320 check return value of scsi_register()
 *      20010320 Version 0.4.3
 *      20010408 Identify version on module load.
 *      20011003 Fix multiple requests
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/random.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/usb.h>
#include <linux/proc_fs.h>

#include <linux/atomic.h>
#include <linux/blkdev.h>
#include "../../scsi/scsi.h"
#include <scsi/scsi_host.h>

#include "microtek.h"

#define DRIVER_AUTHOR "John Fremlin <vii@penguinpowered.com>, Oliver Neukum <Oliver.Neukum@lrz.uni-muenchen.de>"
#define DRIVER_DESC "Microtek Scanmaker X6 USB scanner driver"

/* Should we do debugging? */

//#define MTS_DO_DEBUG

/* USB layer driver interface */

static int mts_usb_probe(struct usb_interface *intf,
                         const struct usb_device_id *id);
static void mts_usb_disconnect(struct usb_interface *intf);

static const struct usb_device_id mts_usb_ids[];

static struct usb_driver mts_usb_driver = {
        .name =         "microtekX6",
        .probe =        mts_usb_probe,
        .disconnect =   mts_usb_disconnect,
        .id_table =     mts_usb_ids,
};


/* Internal driver stuff */

#define MTS_VERSION     "0.4.3"
#define MTS_NAME        "microtek usb (rev " MTS_VERSION "): "

#define MTS_WARNING(x...) \
        printk( KERN_WARNING MTS_NAME x )
#define MTS_ERROR(x...) \
        printk( KERN_ERR MTS_NAME x )
#define MTS_INT_ERROR(x...) \
        MTS_ERROR(x)
#define MTS_MESSAGE(x...) \
        printk( KERN_INFO MTS_NAME x )

#if defined MTS_DO_DEBUG

#define MTS_DEBUG(x...) \
        printk( KERN_DEBUG MTS_NAME x )

#define MTS_DEBUG_GOT_HERE() \
        MTS_DEBUG("got to %s:%d (%s)\n", __FILE__, (int)__LINE__, __func__ )
#define MTS_DEBUG_INT() \
        do { MTS_DEBUG_GOT_HERE(); \
             MTS_DEBUG("transfer = 0x%x context = 0x%x\n",(int)transfer,(int)context ); \
             MTS_DEBUG("status = 0x%x data-length = 0x%x sent = 0x%x\n",transfer->status,(int)context->data_length, (int)transfer->actual_length ); \
             mts_debug_dump(context->instance);\
           } while(0)
#else

#define MTS_NUL_STATEMENT do { } while(0)

#define MTS_DEBUG(x...) MTS_NUL_STATEMENT
#define MTS_DEBUG_GOT_HERE() MTS_NUL_STATEMENT
#define MTS_DEBUG_INT() MTS_NUL_STATEMENT

#endif



#define MTS_INT_INIT()\
        struct mts_transfer_context* context = (struct mts_transfer_context*)transfer->context; \
        MTS_DEBUG_INT();\

#ifdef MTS_DO_DEBUG

static inline void mts_debug_dump(struct mts_desc* desc) {
        MTS_DEBUG("desc at 0x%x: toggle = %02x%02x\n",
                  (int)desc,
                  (int)desc->usb_dev->toggle[1],(int)desc->usb_dev->toggle[0]
                );
        MTS_DEBUG("ep_out=%x ep_response=%x ep_image=%x\n",
                  usb_sndbulkpipe(desc->usb_dev,desc->ep_out),
                  usb_rcvbulkpipe(desc->usb_dev,desc->ep_response),
                  usb_rcvbulkpipe(desc->usb_dev,desc->ep_image)
                );
}


static inline void mts_show_command(struct scsi_cmnd *srb)
{
        char *what = NULL;

        switch (srb->cmnd[0]) {
        case TEST_UNIT_READY: what = "TEST_UNIT_READY"; break;
        case REZERO_UNIT: what = "REZERO_UNIT"; break;
        case REQUEST_SENSE: what = "REQUEST_SENSE"; break;
        case FORMAT_UNIT: what = "FORMAT_UNIT"; break;
        case READ_BLOCK_LIMITS: what = "READ_BLOCK_LIMITS"; break;
        case REASSIGN_BLOCKS: what = "REASSIGN_BLOCKS"; break;
        case READ_6: what = "READ_6"; break;
        case WRITE_6: what = "WRITE_6"; break;
        case SEEK_6: what = "SEEK_6"; break;
        case READ_REVERSE: what = "READ_REVERSE"; break;
        case WRITE_FILEMARKS: what = "WRITE_FILEMARKS"; break;
        case SPACE: what = "SPACE"; break;
        case INQUIRY: what = "INQUIRY"; break;
        case RECOVER_BUFFERED_DATA: what = "RECOVER_BUFFERED_DATA"; break;
        case MODE_SELECT: what = "MODE_SELECT"; break;
        case RESERVE: what = "RESERVE"; break;
        case RELEASE: what = "RELEASE"; break;
        case COPY: what = "COPY"; break;
        case ERASE: what = "ERASE"; break;
        case MODE_SENSE: what = "MODE_SENSE"; break;
        case START_STOP: what = "START_STOP"; break;
        case RECEIVE_DIAGNOSTIC: what = "RECEIVE_DIAGNOSTIC"; break;
        case SEND_DIAGNOSTIC: what = "SEND_DIAGNOSTIC"; break;
        case ALLOW_MEDIUM_REMOVAL: what = "ALLOW_MEDIUM_REMOVAL"; break;
        case SET_WINDOW: what = "SET_WINDOW"; break;
        case READ_CAPACITY: what = "READ_CAPACITY"; break;
        case READ_10: what = "READ_10"; break;
        case WRITE_10: what = "WRITE_10"; break;
        case SEEK_10: what = "SEEK_10"; break;
        case WRITE_VERIFY: what = "WRITE_VERIFY"; break;
        case VERIFY: what = "VERIFY"; break;
        case SEARCH_HIGH: what = "SEARCH_HIGH"; break;
        case SEARCH_EQUAL: what = "SEARCH_EQUAL"; break;
        case SEARCH_LOW: what = "SEARCH_LOW"; break;
        case SET_LIMITS: what = "SET_LIMITS"; break;
        case READ_POSITION: what = "READ_POSITION"; break;
        case SYNCHRONIZE_CACHE: what = "SYNCHRONIZE_CACHE"; break;
        case LOCK_UNLOCK_CACHE: what = "LOCK_UNLOCK_CACHE"; break;
        case READ_DEFECT_DATA: what = "READ_DEFECT_DATA"; break;
        case MEDIUM_SCAN: what = "MEDIUM_SCAN"; break;
        case COMPARE: what = "COMPARE"; break;
        case COPY_VERIFY: what = "COPY_VERIFY"; break;
        case WRITE_BUFFER: what = "WRITE_BUFFER"; break;
        case READ_BUFFER: what = "READ_BUFFER"; break;
        case UPDATE_BLOCK: what = "UPDATE_BLOCK"; break;
        case READ_LONG: what = "READ_LONG"; break;
        case WRITE_LONG: what = "WRITE_LONG"; break;
        case CHANGE_DEFINITION: what = "CHANGE_DEFINITION"; break;
        case WRITE_SAME: what = "WRITE_SAME"; break;
        case READ_TOC: what = "READ_TOC"; break;
        case LOG_SELECT: what = "LOG_SELECT"; break;
        case LOG_SENSE: what = "LOG_SENSE"; break;
        case MODE_SELECT_10: what = "MODE_SELECT_10"; break;
        case MODE_SENSE_10: what = "MODE_SENSE_10"; break;
        case MOVE_MEDIUM: what = "MOVE_MEDIUM"; break;
        case READ_12: what = "READ_12"; break;
        case WRITE_12: what = "WRITE_12"; break;
        case WRITE_VERIFY_12: what = "WRITE_VERIFY_12"; break;
        case SEARCH_HIGH_12: what = "SEARCH_HIGH_12"; break;
        case SEARCH_EQUAL_12: what = "SEARCH_EQUAL_12"; break;
        case SEARCH_LOW_12: what = "SEARCH_LOW_12"; break;
        case READ_ELEMENT_STATUS: what = "READ_ELEMENT_STATUS"; break;
        case SEND_VOLUME_TAG: what = "SEND_VOLUME_TAG"; break;
        case WRITE_LONG_2: what = "WRITE_LONG_2"; break;
        default:
                MTS_DEBUG("can't decode command\n");
                goto out;
                break;
        }
        MTS_DEBUG( "Command %s (%d bytes)\n", what, srb->cmd_len);

 out:
        MTS_DEBUG( "  %10ph\n", srb->cmnd);
}

#else

static inline void mts_show_command(struct scsi_cmnd * dummy)
{
}

static inline void mts_debug_dump(struct mts_desc* dummy)
{
}

#endif

static inline void mts_urb_abort(struct mts_desc* desc) {
        MTS_DEBUG_GOT_HERE();
        mts_debug_dump(desc);

        usb_kill_urb( desc->urb );
}

static int mts_slave_alloc (struct scsi_device *s)
{
        s->inquiry_len = 0x24;
        return 0;
}

static int mts_slave_configure (struct scsi_device *s)
{
        blk_queue_dma_alignment(s->request_queue, (512 - 1));
        return 0;
}

static int mts_scsi_abort(struct scsi_cmnd *srb)
{
        struct mts_desc* desc = (struct mts_desc*)(srb->device->host->hostdata[0]);

        MTS_DEBUG_GOT_HERE();

        mts_urb_abort(desc);

        return FAILED;
}

static int mts_scsi_host_reset(struct scsi_cmnd *srb)
{
        struct mts_desc* desc = (struct mts_desc*)(srb->device->host->hostdata[0]);
        int result;

        MTS_DEBUG_GOT_HERE();
        mts_debug_dump(desc);

        result = usb_lock_device_for_reset(desc->usb_dev, desc->usb_intf);
        if (result == 0) {
                result = usb_reset_device(desc->usb_dev);
                usb_unlock_device(desc->usb_dev);
        }
        return result ? FAILED : SUCCESS;
}

static int
mts_scsi_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *srb);

static void mts_transfer_cleanup( struct urb *transfer );
static void mts_do_sg(struct urb * transfer);

static inline
void mts_int_submit_urb (struct urb* transfer,
                        int pipe,
                        void* data,
                        unsigned length,
                        usb_complete_t callback )
/* Interrupt context! */

/* Holding transfer->context->lock! */
{
        int res;

        MTS_INT_INIT();

        usb_fill_bulk_urb(transfer,
                      context->instance->usb_dev,
                      pipe,
                      data,
                      length,
                      callback,
                      context
                );

        res = usb_submit_urb( transfer, GFP_ATOMIC );
        if ( unlikely(res) ) {
                MTS_INT_ERROR( "could not submit URB! Error was %d\n",(int)res );
                context->srb->result = DID_ERROR << 16;
                mts_transfer_cleanup(transfer);
        }
}


static void mts_transfer_cleanup( struct urb *transfer )
/* Interrupt context! */
{
        MTS_INT_INIT();

        if ( likely(context->final_callback != NULL) )
                context->final_callback(context->srb);
}

static void mts_transfer_done( struct urb *transfer )
{
        MTS_INT_INIT();

        context->srb->result &= MTS_SCSI_ERR_MASK;
        context->srb->result |= (unsigned)(*context->scsi_status)<<1;

        mts_transfer_cleanup(transfer);
}


static void mts_get_status( struct urb *transfer )
/* Interrupt context! */
{
        MTS_INT_INIT();

        mts_int_submit_urb(transfer,
                           usb_rcvbulkpipe(context->instance->usb_dev,
                                           context->instance->ep_response),
                           context->scsi_status,
                           1,
                           mts_transfer_done );
}

static void mts_data_done( struct urb* transfer )
/* Interrupt context! */
{
        int status = transfer->status;
        MTS_INT_INIT();

        if ( context->data_length != transfer->actual_length ) {
                scsi_set_resid(context->srb, context->data_length -
                               transfer->actual_length);
        } else if ( unlikely(status) ) {
                context->srb->result = (status == -ENOENT ? DID_ABORT : DID_ERROR)<<16;
        }

        mts_get_status(transfer);
}


static void mts_command_done( struct urb *transfer )
/* Interrupt context! */
{
        int status = transfer->status;
        MTS_INT_INIT();

        if ( unlikely(status) ) {
                if (status == -ENOENT) {
                        /* We are being killed */
                        MTS_DEBUG_GOT_HERE();
                        context->srb->result = DID_ABORT<<16;
                } else {
                        /* A genuine error has occurred */
                        MTS_DEBUG_GOT_HERE();

                        context->srb->result = DID_ERROR<<16;
                }
                mts_transfer_cleanup(transfer);

                return;
        }

        if (context->srb->cmnd[0] == REQUEST_SENSE) {
                mts_int_submit_urb(transfer,
                                   context->data_pipe,
                                   context->srb->sense_buffer,
                                   context->data_length,
                                   mts_data_done);
        } else { if ( context->data ) {
                        mts_int_submit_urb(transfer,
                                           context->data_pipe,
                                           context->data,
                                           context->data_length,
                                           scsi_sg_count(context->srb) > 1 ?
                                                   mts_do_sg : mts_data_done);
                } else {
                        mts_get_status(transfer);
                }
        }
}

static void mts_do_sg (struct urb* transfer)
{
        struct scatterlist * sg;
        int status = transfer->status;
        MTS_INT_INIT();

        MTS_DEBUG("Processing fragment %d of %d\n", context->fragment,
                                                  scsi_sg_count(context->srb));

        if (unlikely(status)) {
                context->srb->result = (status == -ENOENT ? DID_ABORT : DID_ERROR)<<16;
                mts_transfer_cleanup(transfer);
        }

        sg = scsi_sglist(context->srb);
        context->fragment++;
        mts_int_submit_urb(transfer,
                           context->data_pipe,
                           sg_virt(&sg[context->fragment]),
                           sg[context->fragment].length,
                           context->fragment + 1 == scsi_sg_count(context->srb) ?
                           mts_data_done : mts_do_sg);
}

static const u8 mts_read_image_sig[] = { 0x28, 00, 00, 00 };
static const u8 mts_read_image_sig_len = 4;
static const unsigned char mts_direction[256/8] = {
        0x28, 0x81, 0x14, 0x14, 0x20, 0x01, 0x90, 0x77,
        0x0C, 0x20, 0x00, 0x04, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};


#define MTS_DIRECTION_IS_IN(x) ((mts_direction[x>>3] >> (x & 7)) & 1)

static void
mts_build_transfer_context(struct scsi_cmnd *srb, struct mts_desc* desc)
{
        int pipe;
        struct scatterlist * sg;
        
        MTS_DEBUG_GOT_HERE();

        desc->context.instance = desc;
        desc->context.srb = srb;
        desc->context.fragment = 0;

        if (!scsi_bufflen(srb)) {
                desc->context.data = NULL;
                desc->context.data_length = 0;
                return;
        } else {
                sg = scsi_sglist(srb);
                desc->context.data = sg_virt(&sg[0]);
                desc->context.data_length = sg[0].length;
        }


        /* can't rely on srb->sc_data_direction */

        /* Brutally ripped from usb-storage */

        if ( !memcmp( srb->cmnd, mts_read_image_sig, mts_read_image_sig_len )
) {             pipe = usb_rcvbulkpipe(desc->usb_dev,desc->ep_image);
                MTS_DEBUG( "transferring from desc->ep_image == %d\n",
                           (int)desc->ep_image );
        } else if ( MTS_DIRECTION_IS_IN(srb->cmnd[0]) ) {
                        pipe = usb_rcvbulkpipe(desc->usb_dev,desc->ep_response);
                        MTS_DEBUG( "transferring from desc->ep_response == %d\n",
                                   (int)desc->ep_response);
        } else {
                MTS_DEBUG("transferring to desc->ep_out == %d\n",
                          (int)desc->ep_out);
                pipe = usb_sndbulkpipe(desc->usb_dev,desc->ep_out);
        }
        desc->context.data_pipe = pipe;
}


static int
mts_scsi_queuecommand_lck(struct scsi_cmnd *srb, mts_scsi_cmnd_callback callback)
{
        struct mts_desc* desc = (struct mts_desc*)(srb->device->host->hostdata[0]);
        int err = 0;
        int res;

        MTS_DEBUG_GOT_HERE();
        mts_show_command(srb);
        mts_debug_dump(desc);

        if ( srb->device->lun || srb->device->id || srb->device->channel ) {

                MTS_DEBUG("Command to LUN=%d ID=%d CHANNEL=%d from SCSI layer\n",(int)srb->device->lun,(int)srb->device->id, (int)srb->device->channel );

                MTS_DEBUG("this device doesn't exist\n");

                srb->result = DID_BAD_TARGET << 16;

                if(likely(callback != NULL))
                        callback(srb);

                goto out;
        }

        
        usb_fill_bulk_urb(desc->urb,
                      desc->usb_dev,
                      usb_sndbulkpipe(desc->usb_dev,desc->ep_out),
                      srb->cmnd,
                      srb->cmd_len,
                      mts_command_done,
                      &desc->context
                      );


        mts_build_transfer_context( srb, desc );
        desc->context.final_callback = callback;
        
        /* here we need ATOMIC as we are called with the iolock */
        res=usb_submit_urb(desc->urb, GFP_ATOMIC);

        if(unlikely(res)){
                MTS_ERROR("error %d submitting URB\n",(int)res);
                srb->result = DID_ERROR << 16;

                if(likely(callback != NULL))
                        callback(srb);

        }
out:
        return err;
}

static DEF_SCSI_QCMD(mts_scsi_queuecommand)

static struct scsi_host_template mts_scsi_host_template = {
        .module                 = THIS_MODULE,
        .name                   = "microtekX6",
        .proc_name              = "microtekX6",
        .queuecommand           = mts_scsi_queuecommand,
        .eh_abort_handler       = mts_scsi_abort,
        .eh_host_reset_handler  = mts_scsi_host_reset,
        .sg_tablesize =         SG_ALL,
        .can_queue =            1,
        .this_id =              -1,
        .use_clustering =       1,
        .emulated =             1,
        .slave_alloc =          mts_slave_alloc,
        .slave_configure =      mts_slave_configure,
        .max_sectors=           256, /* 128 K */
};

/* The entries of microtek_table must correspond, line-by-line to
   the entries of mts_supported_products[]. */

static const struct usb_device_id mts_usb_ids[] =
{
        { USB_DEVICE(0x4ce, 0x0300) },
        { USB_DEVICE(0x5da, 0x0094) },
        { USB_DEVICE(0x5da, 0x0099) },
        { USB_DEVICE(0x5da, 0x009a) },
        { USB_DEVICE(0x5da, 0x00a0) },
        { USB_DEVICE(0x5da, 0x00a3) },
        { USB_DEVICE(0x5da, 0x80a3) },
        { USB_DEVICE(0x5da, 0x80ac) },
        { USB_DEVICE(0x5da, 0x00b6) },
        { }                                             /* Terminating entry */
};

MODULE_DEVICE_TABLE (usb, mts_usb_ids);


static int mts_usb_probe(struct usb_interface *intf,
                         const struct usb_device_id *id)
{
        int i;
        int ep_out = -1;
        int ep_in_set[3]; /* this will break if we have more than three endpoints
                           which is why we check */
        int *ep_in_current = ep_in_set;
        int err_retval = -ENOMEM;

        struct mts_desc * new_desc;
        struct usb_device *dev = interface_to_usbdev (intf);

        /* the current altsetting on the interface we're probing */
        struct usb_host_interface *altsetting;

        MTS_DEBUG_GOT_HERE();
        MTS_DEBUG( "usb-device descriptor at %x\n", (int)dev );

        MTS_DEBUG( "product id = 0x%x, vendor id = 0x%x\n",
                   le16_to_cpu(dev->descriptor.idProduct),
                   le16_to_cpu(dev->descriptor.idVendor) );

        MTS_DEBUG_GOT_HERE();

        /* the current altsetting on the interface we're probing */
        altsetting = intf->cur_altsetting;


        /* Check if the config is sane */

        if ( altsetting->desc.bNumEndpoints != MTS_EP_TOTAL ) {
                MTS_WARNING( "expecting %d got %d endpoints! Bailing out.\n",
                             (int)MTS_EP_TOTAL, (int)altsetting->desc.bNumEndpoints );
                return -ENODEV;
        }

        for( i = 0; i < altsetting->desc.bNumEndpoints; i++ ) {
                if ((altsetting->endpoint[i].desc.bmAttributes &
                     USB_ENDPOINT_XFERTYPE_MASK) != USB_ENDPOINT_XFER_BULK) {

                        MTS_WARNING( "can only deal with bulk endpoints; endpoint %d is not bulk.\n",
                             (int)altsetting->endpoint[i].desc.bEndpointAddress );
                } else {
                        if (altsetting->endpoint[i].desc.bEndpointAddress &
                            USB_DIR_IN)
                                *ep_in_current++
                                        = altsetting->endpoint[i].desc.bEndpointAddress &
                                        USB_ENDPOINT_NUMBER_MASK;
                        else {
                                if ( ep_out != -1 ) {
                                        MTS_WARNING( "can only deal with one output endpoints. Bailing out." );
                                        return -ENODEV;
                                }

                                ep_out = altsetting->endpoint[i].desc.bEndpointAddress &
                                        USB_ENDPOINT_NUMBER_MASK;
                        }
                }

        }


        if ( ep_out == -1 ) {
                MTS_WARNING( "couldn't find an output bulk endpoint. Bailing out.\n" );
                return -ENODEV;
        }


        new_desc = kzalloc(sizeof(struct mts_desc), GFP_KERNEL);
        if (!new_desc)
                goto out;

        new_desc->urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!new_desc->urb)
                goto out_kfree;

        new_desc->context.scsi_status = kmalloc(1, GFP_KERNEL);
        if (!new_desc->context.scsi_status)
                goto out_free_urb;

        new_desc->usb_dev = dev;
        new_desc->usb_intf = intf;

        /* endpoints */
        new_desc->ep_out = ep_out;
        new_desc->ep_response = ep_in_set[0];
        new_desc->ep_image = ep_in_set[1];

        if ( new_desc->ep_out != MTS_EP_OUT )
                MTS_WARNING( "will this work? Command EP is not usually %d\n",
                             (int)new_desc->ep_out );

        if ( new_desc->ep_response != MTS_EP_RESPONSE )
                MTS_WARNING( "will this work? Response EP is not usually %d\n",
                             (int)new_desc->ep_response );

        if ( new_desc->ep_image != MTS_EP_IMAGE )
                MTS_WARNING( "will this work? Image data EP is not usually %d\n",
                             (int)new_desc->ep_image );

        new_desc->host = scsi_host_alloc(&mts_scsi_host_template,
                        sizeof(new_desc));
        if (!new_desc->host)
                goto out_kfree2;

        new_desc->host->hostdata[0] = (unsigned long)new_desc;
        if (scsi_add_host(new_desc->host, &dev->dev)) {
                err_retval = -EIO;
                goto out_host_put;
        }
        scsi_scan_host(new_desc->host);

        usb_set_intfdata(intf, new_desc);
        return 0;

 out_host_put:
        scsi_host_put(new_desc->host);
 out_kfree2:
        kfree(new_desc->context.scsi_status);
 out_free_urb:
        usb_free_urb(new_desc->urb);
 out_kfree:
        kfree(new_desc);
 out:
        return err_retval;
}

static void mts_usb_disconnect (struct usb_interface *intf)
{
        struct mts_desc *desc = usb_get_intfdata(intf);

        usb_set_intfdata(intf, NULL);

        usb_kill_urb(desc->urb);
        scsi_remove_host(desc->host);

        scsi_host_put(desc->host);
        usb_free_urb(desc->urb);
        kfree(desc->context.scsi_status);
        kfree(desc);
}

module_usb_driver(mts_usb_driver);

MODULE_AUTHOR( DRIVER_AUTHOR );
MODULE_DESCRIPTION( DRIVER_DESC );
MODULE_LICENSE("GPL");