/*
 * The low performance USB storage driver (ub).
 *
 * Copyright (c) 1999, 2000 Matthew Dharm (mdharm-usb@one-eyed-alien.net)
 * Copyright (C) 2004 Pete Zaitcev (zaitcev@yahoo.com)
 *
 * This work is a part of Linux kernel, is derived from it,
 * and is not licensed separately. See file COPYING for details.
 *
 * TODO (sorted by decreasing priority)
 *  -- Return sense now that rq allows it (we always auto-sense anyway).
 *  -- set readonly flag for CDs, set removable flag for CF readers
 *  -- do inquiry and verify we got a disk and not a tape (for LUN mismatch)
 *  -- verify the 13 conditions and do bulk resets
 *  -- highmem
 *  -- move top_sense and work_bcs into separate allocations (if they survive)
 *     for cache purists and esoteric architectures.
 *  -- Allocate structure for LUN 0 before the first ub_sync_tur, avoid NULL. ?
 *  -- prune comments, they are too volumnous
 *  -- Resove XXX's
 *  -- CLEAR, CLR2STS, CLRRS seem to be ripe for refactoring.
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/usb_usual.h>
#include <linux/blkdev.h>
#include <linux/timer.h>
#include <linux/scatterlist.h>
#include <scsi/scsi.h>

#define DRV_NAME "ub"

#define UB_MAJOR 180

/*
 * The command state machine is the key model for understanding of this driver.
 *
 * The general rule is that all transitions are done towards the bottom
 * of the diagram, thus preventing any loops.
 *
 * An exception to that is how the STAT state is handled. A counter allows it
 * to be re-entered along the path marked with [C].
 *
 *       +--------+
 *       ! INIT   !
 *       +--------+
 *           !
 *        ub_scsi_cmd_start fails ->--------------------------------------\
 *           !                                                            !
 *           V                                                            !
 *       +--------+                                                       !
 *       ! CMD    !                                                       !
 *       +--------+                                                       !
 *           !                                            +--------+      !
 *         was -EPIPE -->-------------------------------->! CLEAR  !      !
 *           !                                            +--------+      !
 *           !                                                !           !
 *         was error -->------------------------------------- ! --------->\
 *           !                                                !           !
 *  /--<-- cmd->dir == NONE ?                                 !           !
 *  !        !                                                !           !
 *  !        V                                                !           !
 *  !    +--------+                                           !           !
 *  !    ! DATA   !                                           !           !
 *  !    +--------+                                           !           !
 *  !        !                           +---------+          !           !
 *  !      was -EPIPE -->--------------->! CLR2STS !          !           !
 *  !        !                           +---------+          !           !
 *  !        !                                !               !           !
 *  !        !                              was error -->---- ! --------->\
 *  !      was error -->--------------------- ! ------------- ! --------->\
 *  !        !                                !               !           !
 *  !        V                                !               !           !
 *  \--->+--------+                           !               !           !
 *       ! STAT   !<--------------------------/               !           !
 *  /--->+--------+                                           !           !
 *  !        !                                                !           !
 * [C]     was -EPIPE -->-----------\                         !           !
 *  !        !                      !                         !           !
 *  +<---- len == 0                 !                         !           !
 *  !        !                      !                         !           !
 *  !      was error -->--------------------------------------!---------->\
 *  !        !                      !                         !           !
 *  +<---- bad CSW                  !                         !           !
 *  +<---- bad tag                  !                         !           !
 *  !        !                      V                         !           !
 *  !        !                 +--------+                     !           !
 *  !        !                 ! CLRRS  !                     !           !
 *  !        !                 +--------+                     !           !
 *  !        !                      !                         !           !
 *  \------- ! --------------------[C]--------\               !           !
 *           !                                !               !           !
 *         cmd->error---\                +--------+           !           !
 *           !          +--------------->! SENSE  !<----------/           !
 *         STAT_FAIL----/                +--------+                       !
 *           !                                !                           V
 *           !                                V                      +--------+
 *           \--------------------------------\--------------------->! DONE   !
 *                                                                   +--------+
 */

/*
 * This many LUNs per USB device.
 * Every one of them takes a host, see UB_MAX_HOSTS.
 */
#define UB_MAX_LUNS   9

/*
 */

#define UB_PARTS_PER_LUN      8

#define UB_MAX_CDB_SIZE      16         /* Corresponds to Bulk */

#define UB_SENSE_SIZE  18

/*
 */

/* command block wrapper */
struct bulk_cb_wrap {
        __le32  Signature;              /* contains 'USBC' */
        u32     Tag;                    /* unique per command id */
        __le32  DataTransferLength;     /* size of data */
        u8      Flags;                  /* direction in bit 0 */
        u8      Lun;                    /* LUN */
        u8      Length;                 /* of of the CDB */
        u8      CDB[UB_MAX_CDB_SIZE];   /* max command */
};

#define US_BULK_CB_WRAP_LEN     31
#define US_BULK_CB_SIGN         0x43425355      /*spells out USBC */
#define US_BULK_FLAG_IN         1
#define US_BULK_FLAG_OUT        0

/* command status wrapper */
struct bulk_cs_wrap {
        __le32  Signature;              /* should = 'USBS' */
        u32     Tag;                    /* same as original command */
        __le32  Residue;                /* amount not transferred */
        u8      Status;                 /* see below */
};

#define US_BULK_CS_WRAP_LEN     13
#define US_BULK_CS_SIGN         0x53425355      /* spells out 'USBS' */
#define US_BULK_STAT_OK         0
#define US_BULK_STAT_FAIL       1
#define US_BULK_STAT_PHASE      2

/* bulk-only class specific requests */
#define US_BULK_RESET_REQUEST   0xff
#define US_BULK_GET_MAX_LUN     0xfe

/*
 */
struct ub_dev;

#define UB_MAX_REQ_SG   9       /* cdrecord requires 32KB and maybe a header */
#define UB_MAX_SECTORS 64

/*
 * A second is more than enough for a 32K transfer (UB_MAX_SECTORS)
 * even if a webcam hogs the bus, but some devices need time to spin up.
 */
#define UB_URB_TIMEOUT  (HZ*2)
#define UB_DATA_TIMEOUT (HZ*5)  /* ZIP does spin-ups in the data phase */
#define UB_STAT_TIMEOUT (HZ*5)  /* Same spinups and eject for a dataless cmd. */
#define UB_CTRL_TIMEOUT (HZ/2)  /* 500ms ought to be enough to clear a stall */

/*
 * An instance of a SCSI command in transit.
 */
#define UB_DIR_NONE     0
#define UB_DIR_READ     1
#define UB_DIR_ILLEGAL2 2
#define UB_DIR_WRITE    3

#define UB_DIR_CHAR(c)  (((c)==UB_DIR_WRITE)? 'w': \
                         (((c)==UB_DIR_READ)? 'r': 'n'))

enum ub_scsi_cmd_state {
        UB_CMDST_INIT,                  /* Initial state */
        UB_CMDST_CMD,                   /* Command submitted */
        UB_CMDST_DATA,                  /* Data phase */
        UB_CMDST_CLR2STS,               /* Clearing before requesting status */
        UB_CMDST_STAT,                  /* Status phase */
        UB_CMDST_CLEAR,                 /* Clearing a stall (halt, actually) */
        UB_CMDST_CLRRS,                 /* Clearing before retrying status */
        UB_CMDST_SENSE,                 /* Sending Request Sense */
        UB_CMDST_DONE                   /* Final state */
};

struct ub_scsi_cmd {
        unsigned char cdb[UB_MAX_CDB_SIZE];
        unsigned char cdb_len;

        unsigned char dir;              /* 0 - none, 1 - read, 3 - write. */
        enum ub_scsi_cmd_state state;
        unsigned int tag;
        struct ub_scsi_cmd *next;

        int error;                      /* Return code - valid upon done */
        unsigned int act_len;           /* Return size */
        unsigned char key, asc, ascq;   /* May be valid if error==-EIO */

        int stat_count;                 /* Retries getting status. */
        unsigned int timeo;             /* jiffies until rq->timeout changes */

        unsigned int len;               /* Requested length */
        unsigned int current_sg;
        unsigned int nsg;               /* sgv[nsg] */
        struct scatterlist sgv[UB_MAX_REQ_SG];

        struct ub_lun *lun;
        void (*done)(struct ub_dev *, struct ub_scsi_cmd *);
        void *back;
};

struct ub_request {
        struct request *rq;
        unsigned int current_try;
        unsigned int nsg;               /* sgv[nsg] */
        struct scatterlist sgv[UB_MAX_REQ_SG];
};

/*
 */
struct ub_capacity {
        unsigned long nsec;             /* Linux size - 512 byte sectors */
        unsigned int bsize;             /* Linux hardsect_size */
        unsigned int bshift;            /* Shift between 512 and hard sects */
};

/*
 * This is a direct take-off from linux/include/completion.h
 * The difference is that I do not wait on this thing, just poll.
 * When I want to wait (ub_probe), I just use the stock completion.
 *
 * Note that INIT_COMPLETION takes no lock. It is correct. But why
 * in the bloody hell that thing takes struct instead of pointer to struct
 * is quite beyond me. I just copied it from the stock completion.
 */
struct ub_completion {
        unsigned int done;
        spinlock_t lock;
};

static inline void ub_init_completion(struct ub_completion *x)
{
        x->done = 0;
        spin_lock_init(&x->lock);
}

#define UB_INIT_COMPLETION(x)   ((x).done = 0)

static void ub_complete(struct ub_completion *x)
{
        unsigned long flags;

        spin_lock_irqsave(&x->lock, flags);
        x->done++;
        spin_unlock_irqrestore(&x->lock, flags);
}

static int ub_is_completed(struct ub_completion *x)
{
        unsigned long flags;
        int ret;

        spin_lock_irqsave(&x->lock, flags);
        ret = x->done;
        spin_unlock_irqrestore(&x->lock, flags);
        return ret;
}

/*
 */
struct ub_scsi_cmd_queue {
        int qlen, qmax;
        struct ub_scsi_cmd *head, *tail;
};

/*
 * The block device instance (one per LUN).
 */
struct ub_lun {
        struct ub_dev *udev;
        struct list_head link;
        struct gendisk *disk;
        int id;                         /* Host index */
        int num;                        /* LUN number */
        char name[16];

        int changed;                    /* Media was changed */
        int removable;
        int readonly;

        struct ub_request urq;

        /* Use Ingo's mempool if or when we have more than one command. */
        /*
         * Currently we never need more than one command for the whole device.
         * However, giving every LUN a command is a cheap and automatic way
         * to enforce fairness between them.
         */
        int cmda[1];
        struct ub_scsi_cmd cmdv[1];

        struct ub_capacity capacity; 
};

/*
 * The USB device instance.
 */
struct ub_dev {
        spinlock_t *lock;
        atomic_t poison;                /* The USB device is disconnected */
        int openc;                      /* protected by ub_lock! */
                                        /* kref is too implicit for our taste */
        int reset;                      /* Reset is running */
        int bad_resid;
        unsigned int tagcnt;
        char name[12];
        struct usb_device *dev;
        struct usb_interface *intf;

        struct list_head luns;

        unsigned int send_bulk_pipe;    /* cached pipe values */
        unsigned int recv_bulk_pipe;
        unsigned int send_ctrl_pipe;
        unsigned int recv_ctrl_pipe;

        struct tasklet_struct tasklet;

        struct ub_scsi_cmd_queue cmd_queue;
        struct ub_scsi_cmd top_rqs_cmd; /* REQUEST SENSE */
        unsigned char top_sense[UB_SENSE_SIZE];

        struct ub_completion work_done;
        struct urb work_urb;
        struct timer_list work_timer;
        int last_pipe;                  /* What might need clearing */
        __le32 signature;               /* Learned signature */
        struct bulk_cb_wrap work_bcb;
        struct bulk_cs_wrap work_bcs;
        struct usb_ctrlrequest work_cr;

        struct work_struct reset_work;
        wait_queue_head_t reset_wait;

        int sg_stat[6];
};

/*
 */
static void ub_cleanup(struct ub_dev *sc);
static int ub_request_fn_1(struct ub_lun *lun, struct request *rq);
static void ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
    struct ub_scsi_cmd *cmd, struct ub_request *urq);
static void ub_cmd_build_packet(struct ub_dev *sc, struct ub_lun *lun,
    struct ub_scsi_cmd *cmd, struct ub_request *urq);
static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_end_rq(struct request *rq, unsigned int status,
    unsigned int cmd_len);
static int ub_rw_cmd_retry(struct ub_dev *sc, struct ub_lun *lun,
    struct ub_request *urq, struct ub_scsi_cmd *cmd);
static int ub_submit_scsi(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_urb_complete(struct urb *urb);
static void ub_scsi_action(unsigned long _dev);
static void ub_scsi_dispatch(struct ub_dev *sc);
static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_data_start(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_state_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd, int rc);
static int __ub_state_stat(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_state_stat(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_state_stat_counted(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_state_sense(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static int ub_submit_clear_stall(struct ub_dev *sc, struct ub_scsi_cmd *cmd,
    int stalled_pipe);
static void ub_top_sense_done(struct ub_dev *sc, struct ub_scsi_cmd *scmd);
static void ub_reset_enter(struct ub_dev *sc, int try);
static void ub_reset_task(struct work_struct *work);
static int ub_sync_tur(struct ub_dev *sc, struct ub_lun *lun);
static int ub_sync_read_cap(struct ub_dev *sc, struct ub_lun *lun,
    struct ub_capacity *ret);
static int ub_sync_reset(struct ub_dev *sc);
static int ub_probe_clear_stall(struct ub_dev *sc, int stalled_pipe);
static int ub_probe_lun(struct ub_dev *sc, int lnum);

/*
 */
#ifdef CONFIG_USB_LIBUSUAL

#define ub_usb_ids  storage_usb_ids
#else

static struct usb_device_id ub_usb_ids[] = {
        { USB_INTERFACE_INFO(USB_CLASS_MASS_STORAGE, US_SC_SCSI, US_PR_BULK) },
        { }
};

MODULE_DEVICE_TABLE(usb, ub_usb_ids);
#endif /* CONFIG_USB_LIBUSUAL */

/*
 * Find me a way to identify "next free minor" for add_disk(),
 * and the array disappears the next day. However, the number of
 * hosts has something to do with the naming and /proc/partitions.
 * This has to be thought out in detail before changing.
 * If UB_MAX_HOST was 1000, we'd use a bitmap. Or a better data structure.
 */
#define UB_MAX_HOSTS  26
static char ub_hostv[UB_MAX_HOSTS];

#define UB_QLOCK_NUM 5
static spinlock_t ub_qlockv[UB_QLOCK_NUM];
static int ub_qlock_next = 0;

static DEFINE_SPINLOCK(ub_lock);        /* Locks globals and ->openc */

/*
 * The id allocator.
 *
 * This also stores the host for indexing by minor, which is somewhat dirty.
 */
static int ub_id_get(void)
{
        unsigned long flags;
        int i;

        spin_lock_irqsave(&ub_lock, flags);
        for (i = 0; i < UB_MAX_HOSTS; i++) {
                if (ub_hostv[i] == 0) {
                        ub_hostv[i] = 1;
                        spin_unlock_irqrestore(&ub_lock, flags);
                        return i;
                }
        }
        spin_unlock_irqrestore(&ub_lock, flags);
        return -1;
}

static void ub_id_put(int id)
{
        unsigned long flags;

        if (id < 0 || id >= UB_MAX_HOSTS) {
                printk(KERN_ERR DRV_NAME ": bad host ID %d\n", id);
                return;
        }

        spin_lock_irqsave(&ub_lock, flags);
        if (ub_hostv[id] == 0) {
                spin_unlock_irqrestore(&ub_lock, flags);
                printk(KERN_ERR DRV_NAME ": freeing free host ID %d\n", id);
                return;
        }
        ub_hostv[id] = 0;
        spin_unlock_irqrestore(&ub_lock, flags);
}

/*
 * This is necessitated by the fact that blk_cleanup_queue does not
 * necesserily destroy the queue. Instead, it may merely decrease q->refcnt.
 * Since our blk_init_queue() passes a spinlock common with ub_dev,
 * we have life time issues when ub_cleanup frees ub_dev.
 */
static spinlock_t *ub_next_lock(void)
{
        unsigned long flags;
        spinlock_t *ret;

        spin_lock_irqsave(&ub_lock, flags);
        ret = &ub_qlockv[ub_qlock_next];
        ub_qlock_next = (ub_qlock_next + 1) % UB_QLOCK_NUM;
        spin_unlock_irqrestore(&ub_lock, flags);
        return ret;
}

/*
 * Downcount for deallocation. This rides on two assumptions:
 *  - once something is poisoned, its refcount cannot grow
 *  - opens cannot happen at this time (del_gendisk was done)
 * If the above is true, we can drop the lock, which we need for
 * blk_cleanup_queue(): the silly thing may attempt to sleep.
 * [Actually, it never needs to sleep for us, but it calls might_sleep()]
 */
static void ub_put(struct ub_dev *sc)
{
        unsigned long flags;

        spin_lock_irqsave(&ub_lock, flags);
        --sc->openc;
        if (sc->openc == 0 && atomic_read(&sc->poison)) {
                spin_unlock_irqrestore(&ub_lock, flags);
                ub_cleanup(sc);
        } else {
                spin_unlock_irqrestore(&ub_lock, flags);
        }
}

/*
 * Final cleanup and deallocation.
 */
static void ub_cleanup(struct ub_dev *sc)
{
        struct list_head *p;
        struct ub_lun *lun;
        struct request_queue *q;

        while (!list_empty(&sc->luns)) {
                p = sc->luns.next;
                lun = list_entry(p, struct ub_lun, link);
                list_del(p);

                /* I don't think queue can be NULL. But... Stolen from sx8.c */
                if ((q = lun->disk->queue) != NULL)
                        blk_cleanup_queue(q);
                /*
                 * If we zero disk->private_data BEFORE put_disk, we have
                 * to check for NULL all over the place in open, release,
                 * check_media and revalidate, because the block level
                 * semaphore is well inside the put_disk.
                 * But we cannot zero after the call, because *disk is gone.
                 * The sd.c is blatantly racy in this area.
                 */
                /* disk->private_data = NULL; */
                put_disk(lun->disk);
                lun->disk = NULL;

                ub_id_put(lun->id);
                kfree(lun);
        }

        usb_set_intfdata(sc->intf, NULL);
        usb_put_intf(sc->intf);
        usb_put_dev(sc->dev);
        kfree(sc);
}

/*
 * The "command allocator".
 */
static struct ub_scsi_cmd *ub_get_cmd(struct ub_lun *lun)
{
        struct ub_scsi_cmd *ret;

        if (lun->cmda[0])
                return NULL;
        ret = &lun->cmdv[0];
        lun->cmda[0] = 1;
        return ret;
}

static void ub_put_cmd(struct ub_lun *lun, struct ub_scsi_cmd *cmd)
{
        if (cmd != &lun->cmdv[0]) {
                printk(KERN_WARNING "%s: releasing a foreign cmd %p\n",
                    lun->name, cmd);
                return;
        }
        if (!lun->cmda[0]) {
                printk(KERN_WARNING "%s: releasing a free cmd\n", lun->name);
                return;
        }
        lun->cmda[0] = 0;
}

/*
 * The command queue.
 */
static void ub_cmdq_add(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        struct ub_scsi_cmd_queue *t = &sc->cmd_queue;

        if (t->qlen++ == 0) {
                t->head = cmd;
                t->tail = cmd;
        } else {
                t->tail->next = cmd;
                t->tail = cmd;
        }

        if (t->qlen > t->qmax)
                t->qmax = t->qlen;
}

static void ub_cmdq_insert(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        struct ub_scsi_cmd_queue *t = &sc->cmd_queue;

        if (t->qlen++ == 0) {
                t->head = cmd;
                t->tail = cmd;
        } else {
                cmd->next = t->head;
                t->head = cmd;
        }

        if (t->qlen > t->qmax)
                t->qmax = t->qlen;
}

static struct ub_scsi_cmd *ub_cmdq_pop(struct ub_dev *sc)
{
        struct ub_scsi_cmd_queue *t = &sc->cmd_queue;
        struct ub_scsi_cmd *cmd;

        if (t->qlen == 0)
                return NULL;
        if (--t->qlen == 0)
                t->tail = NULL;
        cmd = t->head;
        t->head = cmd->next;
        cmd->next = NULL;
        return cmd;
}

#define ub_cmdq_peek(sc)  ((sc)->cmd_queue.head)

/*
 * The request function is our main entry point
 */

static void ub_request_fn(struct request_queue *q)
{
        struct ub_lun *lun = q->queuedata;
        struct request *rq;

        while ((rq = elv_next_request(q)) != NULL) {
                if (ub_request_fn_1(lun, rq) != 0) {
                        blk_stop_queue(q);
                        break;
                }
        }
}

static int ub_request_fn_1(struct ub_lun *lun, struct request *rq)
{
        struct ub_dev *sc = lun->udev;
        struct ub_scsi_cmd *cmd;
        struct ub_request *urq;
        int n_elem;

        if (atomic_read(&sc->poison)) {
                blkdev_dequeue_request(rq);
                ub_end_rq(rq, DID_NO_CONNECT << 16, blk_rq_bytes(rq));
                return 0;
        }

        if (lun->changed && !blk_pc_request(rq)) {
                blkdev_dequeue_request(rq);
                ub_end_rq(rq, SAM_STAT_CHECK_CONDITION, blk_rq_bytes(rq));
                return 0;
        }

        if (lun->urq.rq != NULL)
                return -1;
        if ((cmd = ub_get_cmd(lun)) == NULL)
                return -1;
        memset(cmd, 0, sizeof(struct ub_scsi_cmd));

        blkdev_dequeue_request(rq);

        urq = &lun->urq;
        memset(urq, 0, sizeof(struct ub_request));
        urq->rq = rq;

        /*
         * get scatterlist from block layer
         */
        sg_init_table(&urq->sgv[0], UB_MAX_REQ_SG);
        n_elem = blk_rq_map_sg(lun->disk->queue, rq, &urq->sgv[0]);
        if (n_elem < 0) {
                /* Impossible, because blk_rq_map_sg should not hit ENOMEM. */
                printk(KERN_INFO "%s: failed request map (%d)\n",
                    lun->name, n_elem);
                goto drop;
        }
        if (n_elem > UB_MAX_REQ_SG) {   /* Paranoia */
                printk(KERN_WARNING "%s: request with %d segments\n",
                    lun->name, n_elem);
                goto drop;
        }
        urq->nsg = n_elem;
        sc->sg_stat[n_elem < 5 ? n_elem : 5]++;

        if (blk_pc_request(rq)) {
                ub_cmd_build_packet(sc, lun, cmd, urq);
        } else {
                ub_cmd_build_block(sc, lun, cmd, urq);
        }
        cmd->state = UB_CMDST_INIT;
        cmd->lun = lun;
        cmd->done = ub_rw_cmd_done;
        cmd->back = urq;

        cmd->tag = sc->tagcnt++;
        if (ub_submit_scsi(sc, cmd) != 0)
                goto drop;

        return 0;

drop:
        ub_put_cmd(lun, cmd);
        ub_end_rq(rq, DID_ERROR << 16, blk_rq_bytes(rq));
        return 0;
}

static void ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
    struct ub_scsi_cmd *cmd, struct ub_request *urq)
{
        struct request *rq = urq->rq;
        unsigned int block, nblks;

        if (rq_data_dir(rq) == WRITE)
                cmd->dir = UB_DIR_WRITE;
        else
                cmd->dir = UB_DIR_READ;

        cmd->nsg = urq->nsg;
        memcpy(cmd->sgv, urq->sgv, sizeof(struct scatterlist) * cmd->nsg);

        /*
         * build the command
         *
         * The call to blk_queue_hardsect_size() guarantees that request
         * is aligned, but it is given in terms of 512 byte units, always.
         */
        block = rq->sector >> lun->capacity.bshift;
        nblks = rq->nr_sectors >> lun->capacity.bshift;

        cmd->cdb[0] = (cmd->dir == UB_DIR_READ)? READ_10: WRITE_10;
        /* 10-byte uses 4 bytes of LBA: 2147483648KB, 2097152MB, 2048GB */
        cmd->cdb[2] = block >> 24;
        cmd->cdb[3] = block >> 16;
        cmd->cdb[4] = block >> 8;
        cmd->cdb[5] = block;
        cmd->cdb[7] = nblks >> 8;
        cmd->cdb[8] = nblks;
        cmd->cdb_len = 10;

        cmd->len = rq->nr_sectors * 512;
}

static void ub_cmd_build_packet(struct ub_dev *sc, struct ub_lun *lun,
    struct ub_scsi_cmd *cmd, struct ub_request *urq)
{
        struct request *rq = urq->rq;

        if (rq->data_len == 0) {
                cmd->dir = UB_DIR_NONE;
        } else {
                if (rq_data_dir(rq) == WRITE)
                        cmd->dir = UB_DIR_WRITE;
                else
                        cmd->dir = UB_DIR_READ;
        }

        cmd->nsg = urq->nsg;
        memcpy(cmd->sgv, urq->sgv, sizeof(struct scatterlist) * cmd->nsg);

        memcpy(&cmd->cdb, rq->cmd, rq->cmd_len);
        cmd->cdb_len = rq->cmd_len;

        cmd->len = rq->data_len;

        /*
         * To reapply this to every URB is not as incorrect as it looks.
         * In return, we avoid any complicated tracking calculations.
         */
        cmd->timeo = rq->timeout;
}

static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        struct ub_lun *lun = cmd->lun;
        struct ub_request *urq = cmd->back;
        struct request *rq;
        unsigned int scsi_status;
        unsigned int cmd_len;

        rq = urq->rq;

        if (cmd->error == 0) {
                if (blk_pc_request(rq)) {
                        if (cmd->act_len >= rq->data_len)
                                rq->data_len = 0;
                        else
                                rq->data_len -= cmd->act_len;
                        scsi_status = 0;
                } else {
                        if (cmd->act_len != cmd->len) {
                                scsi_status = SAM_STAT_CHECK_CONDITION;
                        } else {
                                scsi_status = 0;
                        }
                }
        } else {
                if (blk_pc_request(rq)) {
                        /* UB_SENSE_SIZE is smaller than SCSI_SENSE_BUFFERSIZE */
                        memcpy(rq->sense, sc->top_sense, UB_SENSE_SIZE);
                        rq->sense_len = UB_SENSE_SIZE;
                        if (sc->top_sense[0] != 0)
                                scsi_status = SAM_STAT_CHECK_CONDITION;
                        else
                                scsi_status = DID_ERROR << 16;
                } else {
                        if (cmd->error == -EIO &&
                            (cmd->key == 0 ||
                             cmd->key == MEDIUM_ERROR ||
                             cmd->key == UNIT_ATTENTION)) {
                                if (ub_rw_cmd_retry(sc, lun, urq, cmd) == 0)
                                        return;
                        }
                        scsi_status = SAM_STAT_CHECK_CONDITION;
                }
        }

        urq->rq = NULL;

        cmd_len = cmd->len;
        ub_put_cmd(lun, cmd);
        ub_end_rq(rq, scsi_status, cmd_len);
        blk_start_queue(lun->disk->queue);
}

static void ub_end_rq(struct request *rq, unsigned int scsi_status,
    unsigned int cmd_len)
{
        int error;
        long rqlen;

        if (scsi_status == 0) {
                error = 0;
        } else {
                error = -EIO;
                rq->errors = scsi_status;
        }
        rqlen = blk_rq_bytes(rq);    /* Oddly enough, this is the residue. */
        if (__blk_end_request(rq, error, cmd_len)) {
                printk(KERN_WARNING DRV_NAME
                    ": __blk_end_request blew, %s-cmd total %u rqlen %ld\n",
                    blk_pc_request(rq)? "pc": "fs", cmd_len, rqlen);
        }
}

static int ub_rw_cmd_retry(struct ub_dev *sc, struct ub_lun *lun,
    struct ub_request *urq, struct ub_scsi_cmd *cmd)
{

        if (atomic_read(&sc->poison))
                return -ENXIO;

        ub_reset_enter(sc, urq->current_try);

        if (urq->current_try >= 3)
                return -EIO;
        urq->current_try++;

        /* Remove this if anyone complains of flooding. */
        printk(KERN_DEBUG "%s: dir %c len/act %d/%d "
            "[sense %x %02x %02x] retry %d\n",
            sc->name, UB_DIR_CHAR(cmd->dir), cmd->len, cmd->act_len,
            cmd->key, cmd->asc, cmd->ascq, urq->current_try);

        memset(cmd, 0, sizeof(struct ub_scsi_cmd));
        ub_cmd_build_block(sc, lun, cmd, urq);

        cmd->state = UB_CMDST_INIT;
        cmd->lun = lun;
        cmd->done = ub_rw_cmd_done;
        cmd->back = urq;

        cmd->tag = sc->tagcnt++;

#if 0 /* Wasteful */
        return ub_submit_scsi(sc, cmd);
#else
        ub_cmdq_add(sc, cmd);
        return 0;
#endif
}

/*
 * Submit a regular SCSI operation (not an auto-sense).
 *
 * The Iron Law of Good Submit Routine is:
 * Zero return - callback is done, Nonzero return - callback is not done.
 * No exceptions.
 *
 * Host is assumed locked.
 */
static int ub_submit_scsi(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{

        if (cmd->state != UB_CMDST_INIT ||
            (cmd->dir != UB_DIR_NONE && cmd->len == 0)) {
                return -EINVAL;
        }

        ub_cmdq_add(sc, cmd);
        /*
         * We can call ub_scsi_dispatch(sc) right away here, but it's a little
         * safer to jump to a tasklet, in case upper layers do something silly.
         */
        tasklet_schedule(&sc->tasklet);
        return 0;
}

/*
 * Submit the first URB for the queued command.
 * This function does not deal with queueing in any way.
 */
static int ub_scsi_cmd_start(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        struct bulk_cb_wrap *bcb;
        int rc;

        bcb = &sc->work_bcb;

        /*
         * ``If the allocation length is eighteen or greater, and a device
         * server returns less than eithteen bytes of data, the application
         * client should assume that the bytes not transferred would have been
         * zeroes had the device server returned those bytes.''
         *
         * We zero sense for all commands so that when a packet request
         * fails it does not return a stale sense.
         */
        memset(&sc->top_sense, 0, UB_SENSE_SIZE);

        /* set up the command wrapper */
        bcb->Signature = cpu_to_le32(US_BULK_CB_SIGN);
        bcb->Tag = cmd->tag;            /* Endianness is not important */
        bcb->DataTransferLength = cpu_to_le32(cmd->len);
        bcb->Flags = (cmd->dir == UB_DIR_READ) ? 0x80 : 0;
        bcb->Lun = (cmd->lun != NULL) ? cmd->lun->num : 0;
        bcb->Length = cmd->cdb_len;

        /* copy the command payload */
        memcpy(bcb->CDB, cmd->cdb, UB_MAX_CDB_SIZE);

        UB_INIT_COMPLETION(sc->work_done);

        sc->last_pipe = sc->send_bulk_pipe;
        usb_fill_bulk_urb(&sc->work_urb, sc->dev, sc->send_bulk_pipe,
            bcb, US_BULK_CB_WRAP_LEN, ub_urb_complete, sc);

        if ((rc = usb_submit_urb(&sc->work_urb, GFP_ATOMIC)) != 0) {
                /* XXX Clear stalls */
                ub_complete(&sc->work_done);
                return rc;
        }

        sc->work_timer.expires = jiffies + UB_URB_TIMEOUT;
        add_timer(&sc->work_timer);

        cmd->state = UB_CMDST_CMD;
        return 0;
}

/*
 * Timeout handler.
 */
static void ub_urb_timeout(unsigned long arg)
{
        struct ub_dev *sc = (struct ub_dev *) arg;
        unsigned long flags;

        spin_lock_irqsave(sc->lock, flags);
        if (!ub_is_completed(&sc->work_done))
                usb_unlink_urb(&sc->work_urb);
        spin_unlock_irqrestore(sc->lock, flags);
}

/*
 * Completion routine for the work URB.
 *
 * This can be called directly from usb_submit_urb (while we have
 * the sc->lock taken) and from an interrupt (while we do NOT have
 * the sc->lock taken). Therefore, bounce this off to a tasklet.
 */
static void ub_urb_complete(struct urb *urb)
{
        struct ub_dev *sc = urb->context;

        ub_complete(&sc->work_done);
        tasklet_schedule(&sc->tasklet);
}

static void ub_scsi_action(unsigned long _dev)
{
        struct ub_dev *sc = (struct ub_dev *) _dev;
        unsigned long flags;

        spin_lock_irqsave(sc->lock, flags);
        ub_scsi_dispatch(sc);

        spin_unlock_irqrestore(sc->lock, flags);
}

static void ub_scsi_dispatch(struct ub_dev *sc)
{
        struct ub_scsi_cmd *cmd;
        int rc;

        while (!sc->reset && (cmd = ub_cmdq_peek(sc)) != NULL) {
                if (cmd->state == UB_CMDST_DONE) {
                        ub_cmdq_pop(sc);
                        (*cmd->done)(sc, cmd);
                } else if (cmd->state == UB_CMDST_INIT) {
                        if ((rc = ub_scsi_cmd_start(sc, cmd)) == 0)
                                break;
                        cmd->error = rc;
                        cmd->state = UB_CMDST_DONE;
                } else {
                        if (!ub_is_completed(&sc->work_done))
                                break;
                        del_timer(&sc->work_timer);
                        ub_scsi_urb_compl(sc, cmd);
                }
        }
}

static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        struct urb *urb = &sc->work_urb;
        struct bulk_cs_wrap *bcs;
        int len;
        int rc;

        if (atomic_read(&sc->poison)) {
                ub_state_done(sc, cmd, -ENODEV);
                return;
        }

        if (cmd->state == UB_CMDST_CLEAR) {
                if (urb->status == -EPIPE) {
                        /*
                         * STALL while clearning STALL.
                         * The control pipe clears itself - nothing to do.
                         */
                        printk(KERN_NOTICE "%s: stall on control pipe\n",
                            sc->name);
                        goto Bad_End;
                }

                /*
                 * We ignore the result for the halt clear.
                 */

                /* reset the endpoint toggle */
                usb_settoggle(sc->dev, usb_pipeendpoint(sc->last_pipe),
                        usb_pipeout(sc->last_pipe), 0);

                ub_state_sense(sc, cmd);

        } else if (cmd->state == UB_CMDST_CLR2STS) {
                if (urb->status == -EPIPE) {
                        printk(KERN_NOTICE "%s: stall on control pipe\n",
                            sc->name);
                        goto Bad_End;
                }

                /*
                 * We ignore the result for the halt clear.
                 */

                /* reset the endpoint toggle */
                usb_settoggle(sc->dev, usb_pipeendpoint(sc->last_pipe),
                        usb_pipeout(sc->last_pipe), 0);

                ub_state_stat(sc, cmd);

        } else if (cmd->state == UB_CMDST_CLRRS) {
                if (urb->status == -EPIPE) {
                        printk(KERN_NOTICE "%s: stall on control pipe\n",
                            sc->name);
                        goto Bad_End;
                }

                /*
                 * We ignore the result for the halt clear.
                 */

                /* reset the endpoint toggle */
                usb_settoggle(sc->dev, usb_pipeendpoint(sc->last_pipe),
                        usb_pipeout(sc->last_pipe), 0);

                ub_state_stat_counted(sc, cmd);

        } else if (cmd->state == UB_CMDST_CMD) {
                switch (urb->status) {
                case 0:
                        break;
                case -EOVERFLOW:
                        goto Bad_End;
                case -EPIPE:
                        rc = ub_submit_clear_stall(sc, cmd, sc->last_pipe);
                        if (rc != 0) {
                                printk(KERN_NOTICE "%s: "
                                    "unable to submit clear (%d)\n",
                                    sc->name, rc);
                                /*
                                 * This is typically ENOMEM or some other such shit.
                                 * Retrying is pointless. Just do Bad End on it...
                                 */
                                ub_state_done(sc, cmd, rc);
                                return;
                        }
                        cmd->state = UB_CMDST_CLEAR;
                        return;
                case -ESHUTDOWN:        /* unplug */
                case -EILSEQ:           /* unplug timeout on uhci */
                        ub_state_done(sc, cmd, -ENODEV);
                        return;
                default:
                        goto Bad_End;
                }
                if (urb->actual_length != US_BULK_CB_WRAP_LEN) {
                        goto Bad_End;
                }

                if (cmd->dir == UB_DIR_NONE || cmd->nsg < 1) {
                        ub_state_stat(sc, cmd);
                        return;
                }

                // udelay(125);         // usb-storage has this
                ub_data_start(sc, cmd);

        } else if (cmd->state == UB_CMDST_DATA) {
                if (urb->status == -EPIPE) {
                        rc = ub_submit_clear_stall(sc, cmd, sc->last_pipe);
                        if (rc != 0) {
                                printk(KERN_NOTICE "%s: "
                                    "unable to submit clear (%d)\n",
                                    sc->name, rc);
                                ub_state_done(sc, cmd, rc);
                                return;
                        }
                        cmd->state = UB_CMDST_CLR2STS;
                        return;
                }
                if (urb->status == -EOVERFLOW) {
                        /*
                         * A babble? Failure, but we must transfer CSW now.
                         */
                        cmd->error = -EOVERFLOW;        /* A cheap trick... */
                        ub_state_stat(sc, cmd);
                        return;
                }

                if (cmd->dir == UB_DIR_WRITE) {
                        /*
                         * Do not continue writes in case of a failure.
                         * Doing so would cause sectors to be mixed up,
                         * which is worse than sectors lost.
                         *
                         * We must try to read the CSW, or many devices
                         * get confused.
                         */
                        len = urb->actual_length;
                        if (urb->status != 0 ||
                            len != cmd->sgv[cmd->current_sg].length) {
                                cmd->act_len += len;

                                cmd->error = -EIO;
                                ub_state_stat(sc, cmd);
                                return;
                        }

                } else {
                        /*
                         * If an error occurs on read, we record it, and
                         * continue to fetch data in order to avoid bubble.
                         *
                         * As a small shortcut, we stop if we detect that
                         * a CSW mixed into data.
                         */
                        if (urb->status != 0)
                                cmd->error = -EIO;

                        len = urb->actual_length;
                        if (urb->status != 0 ||
                            len != cmd->sgv[cmd->current_sg].length) {
                                if ((len & 0x1FF) == US_BULK_CS_WRAP_LEN)
                                        goto Bad_End;
                        }
                }

                cmd->act_len += urb->actual_length;

                if (++cmd->current_sg < cmd->nsg) {
                        ub_data_start(sc, cmd);
                        return;
                }
                ub_state_stat(sc, cmd);

        } else if (cmd->state == UB_CMDST_STAT) {
                if (urb->status == -EPIPE) {
                        rc = ub_submit_clear_stall(sc, cmd, sc->last_pipe);
                        if (rc != 0) {
                                printk(KERN_NOTICE "%s: "
                                    "unable to submit clear (%d)\n",
                                    sc->name, rc);
                                ub_state_done(sc, cmd, rc);
                                return;
                        }

                        /*
                         * Having a stall when getting CSW is an error, so
                         * make sure uppper levels are not oblivious to it.
                         */
                        cmd->error = -EIO;              /* A cheap trick... */

                        cmd->state = UB_CMDST_CLRRS;
                        return;
                }

                /* Catch everything, including -EOVERFLOW and other nasties. */
                if (urb->status != 0)
                        goto Bad_End;

                if (urb->actual_length == 0) {
                        ub_state_stat_counted(sc, cmd);
                        return;
                }

                /*
                 * Check the returned Bulk protocol status.
                 * The status block has to be validated first.
                 */

                bcs = &sc->work_bcs;

                if (sc->signature == cpu_to_le32(0)) {
                        /*
                         * This is the first reply, so do not perform the check.
                         * Instead, remember the signature the device uses
                         * for future checks. But do not allow a nul.
                         */
                        sc->signature = bcs->Signature;
                        if (sc->signature == cpu_to_le32(0)) {
                                ub_state_stat_counted(sc, cmd);
                                return;
                        }
                } else {
                        if (bcs->Signature != sc->signature) {
                                ub_state_stat_counted(sc, cmd);
                                return;
                        }
                }

                if (bcs->Tag != cmd->tag) {
                        /*
                         * This usually happens when we disagree with the
                         * device's microcode about something. For instance,
                         * a few of them throw this after timeouts. They buffer
                         * commands and reply at commands we timed out before.
                         * Without flushing these replies we loop forever.
                         */
                        ub_state_stat_counted(sc, cmd);
                        return;
                }

                if (!sc->bad_resid) {
                        len = le32_to_cpu(bcs->Residue);
                        if (len != cmd->len - cmd->act_len) {
                                /*
                                 * Only start ignoring if this cmd ended well.
                                 */
                                if (cmd->len == cmd->act_len) {
                                        printk(KERN_NOTICE "%s: "
                                            "bad residual %d of %d, ignoring\n",
                                            sc->name, len, cmd->len);
                                        sc->bad_resid = 1;
                                }
                        }
                }

                switch (bcs->Status) {
                case US_BULK_STAT_OK:
                        break;
                case US_BULK_STAT_FAIL:
                        ub_state_sense(sc, cmd);
                        return;
                case US_BULK_STAT_PHASE:
                        goto Bad_End;
                default:
                        printk(KERN_INFO "%s: unknown CSW status 0x%x\n",
                            sc->name, bcs->Status);
                        ub_state_done(sc, cmd, -EINVAL);
                        return;
                }

                /* Not zeroing error to preserve a babble indicator */
                if (cmd->error != 0) {
                        ub_state_sense(sc, cmd);
                        return;
                }
                cmd->state = UB_CMDST_DONE;
                ub_cmdq_pop(sc);
                (*cmd->done)(sc, cmd);

        } else if (cmd->state == UB_CMDST_SENSE) {
                ub_state_done(sc, cmd, -EIO);

        } else {
                printk(KERN_WARNING "%s: wrong command state %d\n",
                    sc->name, cmd->state);
                ub_state_done(sc, cmd, -EINVAL);
                return;
        }
        return;

Bad_End: /* Little Excel is dead */
        ub_state_done(sc, cmd, -EIO);
}

/*
 * Factorization helper for the command state machine:
 * Initiate a data segment transfer.
 */
static void ub_data_start(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        struct scatterlist *sg = &cmd->sgv[cmd->current_sg];
        int pipe;
        int rc;

        UB_INIT_COMPLETION(sc->work_done);

        if (cmd->dir == UB_DIR_READ)
                pipe = sc->recv_bulk_pipe;
        else
                pipe = sc->send_bulk_pipe;
        sc->last_pipe = pipe;
        usb_fill_bulk_urb(&sc->work_urb, sc->dev, pipe, sg_virt(sg),
            sg->length, ub_urb_complete, sc);

        if ((rc = usb_submit_urb(&sc->work_urb, GFP_ATOMIC)) != 0) {
                /* XXX Clear stalls */
                ub_complete(&sc->work_done);
                ub_state_done(sc, cmd, rc);
                return;
        }

        if (cmd->timeo)
                sc->work_timer.expires = jiffies + cmd->timeo;
        else
                sc->work_timer.expires = jiffies + UB_DATA_TIMEOUT;
        add_timer(&sc->work_timer);

        cmd->state = UB_CMDST_DATA;
}

/*
 * Factorization helper for the command state machine:
 * Finish the command.
 */
static void ub_state_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd, int rc)
{

        cmd->error = rc;
        cmd->state = UB_CMDST_DONE;
        ub_cmdq_pop(sc);
        (*cmd->done)(sc, cmd);
}

/*
 * Factorization helper for the command state machine:
 * Submit a CSW read.
 */
static int __ub_state_stat(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        int rc;

        UB_INIT_COMPLETION(sc->work_done);

        sc->last_pipe = sc->recv_bulk_pipe;
        usb_fill_bulk_urb(&sc->work_urb, sc->dev, sc->recv_bulk_pipe,
            &sc->work_bcs, US_BULK_CS_WRAP_LEN, ub_urb_complete, sc);

        if ((rc = usb_submit_urb(&sc->work_urb, GFP_ATOMIC)) != 0) {
                /* XXX Clear stalls */
                ub_complete(&sc->work_done);
                ub_state_done(sc, cmd, rc);
                return -1;
        }

        if (cmd->timeo)
                sc->work_timer.expires = jiffies + cmd->timeo;
        else
                sc->work_timer.expires = jiffies + UB_STAT_TIMEOUT;
        add_timer(&sc->work_timer);
        return 0;
}

/*
 * Factorization helper for the command state machine:
 * Submit a CSW read and go to STAT state.
 */
static void ub_state_stat(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{

        if (__ub_state_stat(sc, cmd) != 0)
                return;

        cmd->stat_count = 0;
        cmd->state = UB_CMDST_STAT;
}

/*
 * Factorization helper for the command state machine:
 * Submit a CSW read and go to STAT state with counter (along [C] path).
 */
static void ub_state_stat_counted(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{

        if (++cmd->stat_count >= 4) {
                ub_state_sense(sc, cmd);
                return;
        }

        if (__ub_state_stat(sc, cmd) != 0)
                return;

        cmd->state = UB_CMDST_STAT;
}

/*
 * Factorization helper for the command state machine:
 * Submit a REQUEST SENSE and go to SENSE state.
 */
static void ub_state_sense(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        struct ub_scsi_cmd *scmd;
        struct scatterlist *sg;
        int rc;

        if (cmd->cdb[0] == REQUEST_SENSE) {
                rc = -EPIPE;
                goto error;
        }

        scmd = &sc->top_rqs_cmd;
        memset(scmd, 0, sizeof(struct ub_scsi_cmd));
        scmd->cdb[0] = REQUEST_SENSE;
        scmd->cdb[4] = UB_SENSE_SIZE;
        scmd->cdb_len = 6;
        scmd->dir = UB_DIR_READ;
        scmd->state = UB_CMDST_INIT;
        scmd->nsg = 1;
        sg = &scmd->sgv[0];
        sg_init_table(sg, UB_MAX_REQ_SG);
        sg_set_page(sg, virt_to_page(sc->top_sense), UB_SENSE_SIZE,
                        (unsigned long)sc->top_sense & (PAGE_SIZE-1));
        scmd->len = UB_SENSE_SIZE;
        scmd->lun = cmd->lun;
        scmd->done = ub_top_sense_done;
        scmd->back = cmd;

        scmd->tag = sc->tagcnt++;

        cmd->state = UB_CMDST_SENSE;

        ub_cmdq_insert(sc, scmd);
        return;

error:
        ub_state_done(sc, cmd, rc);
}

/*
 * A helper for the command's state machine:
 * Submit a stall clear.
 */
static int ub_submit_clear_stall(struct ub_dev *sc, struct ub_scsi_cmd *cmd,
    int stalled_pipe)
{
        int endp;
        struct usb_ctrlrequest *cr;
        int rc;

        endp = usb_pipeendpoint(stalled_pipe);
        if (usb_pipein (stalled_pipe))
                endp |= USB_DIR_IN;

        cr = &sc->work_cr;
        cr->bRequestType = USB_RECIP_ENDPOINT;
        cr->bRequest = USB_REQ_CLEAR_FEATURE;
        cr->wValue = cpu_to_le16(USB_ENDPOINT_HALT);
        cr->wIndex = cpu_to_le16(endp);
        cr->wLength = cpu_to_le16(0);

        UB_INIT_COMPLETION(sc->work_done);

        usb_fill_control_urb(&sc->work_urb, sc->dev, sc->send_ctrl_pipe,
            (unsigned char*) cr, NULL, 0, ub_urb_complete, sc);

        if ((rc = usb_submit_urb(&sc->work_urb, GFP_ATOMIC)) != 0) {
                ub_complete(&sc->work_done);
                return rc;
        }

        sc->work_timer.expires = jiffies + UB_CTRL_TIMEOUT;
        add_timer(&sc->work_timer);
        return 0;
}

/*
 */
static void ub_top_sense_done(struct ub_dev *sc, struct ub_scsi_cmd *scmd)
{
        unsigned char *sense = sc->top_sense;
        struct ub_scsi_cmd *cmd;

        /*
         * Find the command which triggered the unit attention or a check,
         * save the sense into it, and advance its state machine.
         */
        if ((cmd = ub_cmdq_peek(sc)) == NULL) {
                printk(KERN_WARNING "%s: sense done while idle\n", sc->name);
                return;
        }
        if (cmd != scmd->back) {
                printk(KERN_WARNING "%s: "
                    "sense done for wrong command 0x%x\n",
                    sc->name, cmd->tag);
                return;
        }
        if (cmd->state != UB_CMDST_SENSE) {
                printk(KERN_WARNING "%s: sense done with bad cmd state %d\n",
                    sc->name, cmd->state);
                return;
        }

        /*
         * Ignoring scmd->act_len, because the buffer was pre-zeroed.
         */
        cmd->key = sense[2] & 0x0F;
        cmd->asc = sense[12];
        cmd->ascq = sense[13];

        ub_scsi_urb_compl(sc, cmd);
}

/*
 * Reset management
 * XXX Move usb_reset_device to khubd. Hogging kevent is not a good thing.
 * XXX Make usb_sync_reset asynchronous.
 */

static void ub_reset_enter(struct ub_dev *sc, int try)
{

        if (sc->reset) {
                /* This happens often on multi-LUN devices. */
                return;
        }
        sc->reset = try + 1;

#if 0 /* Not needed because the disconnect waits for us. */
        unsigned long flags;
        spin_lock_irqsave(&ub_lock, flags);
        sc->openc++;
        spin_unlock_irqrestore(&ub_lock, flags);
#endif

#if 0 /* We let them stop themselves. */
        struct ub_lun *lun;
        list_for_each_entry(lun, &sc->luns, link) {
                blk_stop_queue(lun->disk->queue);
        }
#endif

        schedule_work(&sc->reset_work);
}

static void ub_reset_task(struct work_struct *work)
{
        struct ub_dev *sc = container_of(work, struct ub_dev, reset_work);
        unsigned long flags;
        struct ub_lun *lun;
        int lkr, rc;

        if (!sc->reset) {
                printk(KERN_WARNING "%s: Running reset unrequested\n",
                    sc->name);
                return;
        }

        if (atomic_read(&sc->poison)) {
                ;
        } else if ((sc->reset & 1) == 0) {
                ub_sync_reset(sc);
                msleep(700);    /* usb-storage sleeps 6s (!) */
                ub_probe_clear_stall(sc, sc->recv_bulk_pipe);
                ub_probe_clear_stall(sc, sc->send_bulk_pipe);
        } else if (sc->dev->actconfig->desc.bNumInterfaces != 1) {
                ;
        } else {
                if ((lkr = usb_lock_device_for_reset(sc->dev, sc->intf)) < 0) {
                        printk(KERN_NOTICE
                            "%s: usb_lock_device_for_reset failed (%d)\n",
                            sc->name, lkr);
                } else {
                        rc = usb_reset_device(sc->dev);
                        if (rc < 0) {
                                printk(KERN_NOTICE "%s: "
                                    "usb_lock_device_for_reset failed (%d)\n",
                                    sc->name, rc);
                        }

                        if (lkr)
                                usb_unlock_device(sc->dev);
                }
        }

        /*
         * In theory, no commands can be running while reset is active,
         * so nobody can ask for another reset, and so we do not need any
         * queues of resets or anything. We do need a spinlock though,
         * to interact with block layer.
         */
        spin_lock_irqsave(sc->lock, flags);
        sc->reset = 0;
        tasklet_schedule(&sc->tasklet);
        list_for_each_entry(lun, &sc->luns, link) {
                blk_start_queue(lun->disk->queue);
        }
        wake_up(&sc->reset_wait);
        spin_unlock_irqrestore(sc->lock, flags);
}

/*
 * This is called from a process context.
 */
static void ub_revalidate(struct ub_dev *sc, struct ub_lun *lun)
{

        lun->readonly = 0;      /* XXX Query this from the device */

        lun->capacity.nsec = 0;
        lun->capacity.bsize = 512;
        lun->capacity.bshift = 0;

        if (ub_sync_tur(sc, lun) != 0)
                return;                 /* Not ready */
        lun->changed = 0;

        if (ub_sync_read_cap(sc, lun, &lun->capacity) != 0) {
                /*
                 * The retry here means something is wrong, either with the
                 * device, with the transport, or with our code.
                 * We keep this because sd.c has retries for capacity.
                 */
                if (ub_sync_read_cap(sc, lun, &lun->capacity) != 0) {
                        lun->capacity.nsec = 0;
                        lun->capacity.bsize = 512;
                        lun->capacity.bshift = 0;
                }
        }
}

/*
 * The open funcion.
 * This is mostly needed to keep refcounting, but also to support
 * media checks on removable media drives.
 */
static int ub_bd_open(struct inode *inode, struct file *filp)
{
        struct gendisk *disk = inode->i_bdev->bd_disk;
        struct ub_lun *lun = disk->private_data;
        struct ub_dev *sc = lun->udev;
        unsigned long flags;
        int rc;

        spin_lock_irqsave(&ub_lock, flags);
        if (atomic_read(&sc->poison)) {
                spin_unlock_irqrestore(&ub_lock, flags);
                return -ENXIO;
        }
        sc->openc++;
        spin_unlock_irqrestore(&ub_lock, flags);

        if (lun->removable || lun->readonly)
                check_disk_change(inode->i_bdev);

        /*
         * The sd.c considers ->media_present and ->changed not equivalent,
         * under some pretty murky conditions (a failure of READ CAPACITY).
         * We may need it one day.
         */
        if (lun->removable && lun->changed && !(filp->f_flags & O_NDELAY)) {
                rc = -ENOMEDIUM;
                goto err_open;
        }

        if (lun->readonly && (filp->f_mode & FMODE_WRITE)) {
                rc = -EROFS;
                goto err_open;
        }

        return 0;

err_open:
        ub_put(sc);
        return rc;
}

/*
 */
static int ub_bd_release(struct inode *inode, struct file *filp)
{
        struct gendisk *disk = inode->i_bdev->bd_disk;
        struct ub_lun *lun = disk->private_data;
        struct ub_dev *sc = lun->udev;

        ub_put(sc);
        return 0;
}

/*
 * The ioctl interface.
 */
static int ub_bd_ioctl(struct inode *inode, struct file *filp,
    unsigned int cmd, unsigned long arg)
{
        void __user *usermem = (void __user *) arg;

        return scsi_cmd_blk_ioctl(filp, inode->i_bdev, cmd, usermem);
}

/*
 * This is called by check_disk_change if we reported a media change.
 * The main onjective here is to discover the features of the media such as
 * the capacity, read-only status, etc. USB storage generally does not
 * need to be spun up, but if we needed it, this would be the place.
 *
 * This call can sleep.
 *
 * The return code is not used.
 */
static int ub_bd_revalidate(struct gendisk *disk)
{
        struct ub_lun *lun = disk->private_data;

        ub_revalidate(lun->udev, lun);

        /* XXX Support sector size switching like in sr.c */
        blk_queue_hardsect_size(disk->queue, lun->capacity.bsize);
        set_capacity(disk, lun->capacity.nsec);
        // set_disk_ro(sdkp->disk, lun->readonly);

        return 0;
}

/*
 * The check is called by the block layer to verify if the media
 * is still available. It is supposed to be harmless, lightweight and
 * non-intrusive in case the media was not changed.
 *
 * This call can sleep.
 *
 * The return code is bool!
 */
static int ub_bd_media_changed(struct gendisk *disk)
{
        struct ub_lun *lun = disk->private_data;

        if (!lun->removable)
                return 0;

        /*
         * We clean checks always after every command, so this is not
         * as dangerous as it looks. If the TEST_UNIT_READY fails here,
         * the device is actually not ready with operator or software
         * intervention required. One dangerous item might be a drive which
         * spins itself down, and come the time to write dirty pages, this
         * will fail, then block layer discards the data. Since we never
         * spin drives up, such devices simply cannot be used with ub anyway.
         */
        if (ub_sync_tur(lun->udev, lun) != 0) {
                lun->changed = 1;
                return 1;
        }

        return lun->changed;
}

static struct block_device_operations ub_bd_fops = {
        .owner          = THIS_MODULE,
        .open           = ub_bd_open,
        .release        = ub_bd_release,
        .ioctl          = ub_bd_ioctl,
        .media_changed  = ub_bd_media_changed,
        .revalidate_disk = ub_bd_revalidate,
};

/*
 * Common ->done routine for commands executed synchronously.
 */
static void ub_probe_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        struct completion *cop = cmd->back;
        complete(cop);
}

/*
 * Test if the device has a check condition on it, synchronously.
 */
static int ub_sync_tur(struct ub_dev *sc, struct ub_lun *lun)
{
        struct ub_scsi_cmd *cmd;
        enum { ALLOC_SIZE = sizeof(struct ub_scsi_cmd) };
        unsigned long flags;
        struct completion compl;
        int rc;

        init_completion(&compl);

        rc = -ENOMEM;
        if ((cmd = kzalloc(ALLOC_SIZE, GFP_KERNEL)) == NULL)
                goto err_alloc;

        cmd->cdb[0] = TEST_UNIT_READY;
        cmd->cdb_len = 6;
        cmd->dir = UB_DIR_NONE;
        cmd->state = UB_CMDST_INIT;
        cmd->lun = lun;                 /* This may be NULL, but that's ok */
        cmd->done = ub_probe_done;
        cmd->back = &compl;

        spin_lock_irqsave(sc->lock, flags);
        cmd->tag = sc->tagcnt++;

        rc = ub_submit_scsi(sc, cmd);
        spin_unlock_irqrestore(sc->lock, flags);

        if (rc != 0)
                goto err_submit;

        wait_for_completion(&compl);

        rc = cmd->error;

        if (rc == -EIO && cmd->key != 0)        /* Retries for benh's key */
                rc = cmd->key;

err_submit:
        kfree(cmd);
err_alloc:
        return rc;
}

/*
 * Read the SCSI capacity synchronously (for probing).
 */
static int ub_sync_read_cap(struct ub_dev *sc, struct ub_lun *lun,
    struct ub_capacity *ret)
{
        struct ub_scsi_cmd *cmd;
        struct scatterlist *sg;
        char *p;
        enum { ALLOC_SIZE = sizeof(struct ub_scsi_cmd) + 8 };
        unsigned long flags;
        unsigned int bsize, shift;
        unsigned long nsec;
        struct completion compl;
        int rc;

        init_completion(&compl);

        rc = -ENOMEM;
        if ((cmd = kzalloc(ALLOC_SIZE, GFP_KERNEL)) == NULL)
                goto err_alloc;
        p = (char *)cmd + sizeof(struct ub_scsi_cmd);

        cmd->cdb[0] = 0x25;
        cmd->cdb_len = 10;
        cmd->dir = UB_DIR_READ;
        cmd->state = UB_CMDST_INIT;
        cmd->nsg = 1;
        sg = &cmd->sgv[0];
        sg_init_table(sg, UB_MAX_REQ_SG);
        sg_set_page(sg, virt_to_page(p), 8, (unsigned long)p & (PAGE_SIZE-1));
        cmd->len = 8;
        cmd->lun = lun;
        cmd->done = ub_probe_done;
        cmd->back = &compl;

        spin_lock_irqsave(sc->lock, flags);
        cmd->tag = sc->tagcnt++;

        rc = ub_submit_scsi(sc, cmd);
        spin_unlock_irqrestore(sc->lock, flags);

        if (rc != 0)
                goto err_submit;

        wait_for_completion(&compl);

        if (cmd->error != 0) {
                rc = -EIO;
                goto err_read;
        }
        if (cmd->act_len != 8) {
                rc = -EIO;
                goto err_read;
        }

        /* sd.c special-cases sector size of 0 to mean 512. Needed? Safe? */
        nsec = be32_to_cpu(*(__be32 *)p) + 1;
        bsize = be32_to_cpu(*(__be32 *)(p + 4));
        switch (bsize) {
        case 512:       shift = 0;      break;
        case 1024:      shift = 1;      break;
        case 2048:      shift = 2;      break;
        case 4096:      shift = 3;      break;
        default:
                rc = -EDOM;
                goto err_inv_bsize;
        }

        ret->bsize = bsize;
        ret->bshift = shift;
        ret->nsec = nsec << shift;
        rc = 0;

err_inv_bsize:
err_read:
err_submit:
        kfree(cmd);
err_alloc:
        return rc;
}

/*
 */
static void ub_probe_urb_complete(struct urb *urb)
{
        struct completion *cop = urb->context;
        complete(cop);
}

static void ub_probe_timeout(unsigned long arg)
{
        struct completion *cop = (struct completion *) arg;
        complete(cop);
}

/*
 * Reset with a Bulk reset.
 */
static int ub_sync_reset(struct ub_dev *sc)
{
        int ifnum = sc->intf->cur_altsetting->desc.bInterfaceNumber;
        struct usb_ctrlrequest *cr;
        struct completion compl;
        struct timer_list timer;
        int rc;

        init_completion(&compl);

        cr = &sc->work_cr;
        cr->bRequestType = USB_TYPE_CLASS | USB_RECIP_INTERFACE;
        cr->bRequest = US_BULK_RESET_REQUEST;
        cr->wValue = cpu_to_le16(0);
        cr->wIndex = cpu_to_le16(ifnum);
        cr->wLength = cpu_to_le16(0);

        usb_fill_control_urb(&sc->work_urb, sc->dev, sc->send_ctrl_pipe,
            (unsigned char*) cr, NULL, 0, ub_probe_urb_complete, &compl);

        if ((rc = usb_submit_urb(&sc->work_urb, GFP_KERNEL)) != 0) {
                printk(KERN_WARNING
                     "%s: Unable to submit a bulk reset (%d)\n", sc->name, rc);
                return rc;
        }

        init_timer(&timer);
        timer.function = ub_probe_timeout;
        timer.data = (unsigned long) &compl;
        timer.expires = jiffies + UB_CTRL_TIMEOUT;
        add_timer(&timer);

        wait_for_completion(&compl);

        del_timer_sync(&timer);
        usb_kill_urb(&sc->work_urb);

        return sc->work_urb.status;
}

/*
 * Get number of LUNs by the way of Bulk GetMaxLUN command.
 */