// SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
/*
 * 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.rst> 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/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 <asm/unaligned.h>

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

#include <linux/nospec.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;
        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;
        void                    *exception_arg;

        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;

        /* Gadget's private data. */
        void                    *private_data;

        char inquiry_string[INQUIRY_STRING_LEN];
};

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);
}

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,
                              void *arg)
{
        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;
                common->exception_arg = arg;
                if (common->thread_task)
                        send_sig_info(SIGUSR1, SEND_SIG_PRIV,
                                      common->thread_task);
        }
        spin_unlock_irqrestore(&common->lock, flags);
}

static void raise_exception(struct fsg_common *common, enum fsg_state new_state)
{
        __raise_exception(common, new_state, NULL);
}

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

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 = kernel_read(curlun->filp, 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 = kernel_write(curlun->filp, 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 = kernel_read(curlun->filp, 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,