Linux-2.6.12-rc2

[~andy/linux] / drivers / block / ub.c

/*
 * 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)
 *  -- Do resets with usb_device_reset (needs a thread context, use khubd)
 *  -- 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)
 *  -- support pphaneuf's SDDR-75 with two LUNs (also broken capacity...)
 *  -- special case some senses, e.g. 3a/0 -> no media present, reduce retries
 *  -- verify the 13 conditions and do bulk resets
 *  -- normal pool of commands instead of cmdv[]?
 *  -- kill last_pipe and simply do two-state clearing on both pipes
 *  -- verify protocol (bulk) from USB descriptors (maybe...)
 *  -- highmem and sg
 *  -- move top_sense and work_bcs into separate allocations (if they survive)
 *     for cache purists and esoteric architectures.
 *  -- prune comments, they are too volumnous
 *  -- Exterminate P3 printks
 *  -- Resove XXX's
 *  -- Redo "benh's retries", perhaps have spin-up code to handle them. V:D=?
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/blkdev.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/timer.h>
#include <scsi/scsi.h>

#define DRV_NAME "ub"
#define DEVFS_NAME DRV_NAME

#define UB_MAJOR 180

/*
 * Definitions which have to be scattered once we understand the layout better.
 */

/* Transport (despite PR in the name) */
#define US_PR_BULK      0x50            /* bulk only */

/* Protocol */
#define US_SC_SCSI      0x06            /* Transparent */

/*
 */
#define UB_MINORS_PER_MAJOR     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 normally 0 */
        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' */
/* This is for Olympus Camedia digital cameras */
#define US_BULK_CS_OLYMPUS_SIGN 0x55425355      /* spells out 'USBU' */
#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   1
#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_SENSE,                 /* Sending Request Sense */
        UB_CMDST_DONE                   /* Final state */
};

static char *ub_scsi_cmd_stname[] = {
        ".  ",
        "Cmd",
        "dat",
        "c2s",
        "sts",
        "clr",
        "Sen",
        "fin"
};

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

        unsigned char dir;              /* 0 - none, 1 - read, 3 - write. */
        unsigned char trace_index;
        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. */

        /*
         * We do not support transfers from highmem pages
         * because the underlying USB framework does not do what we need.
         */
        char *data;                     /* Requested buffer */
        unsigned int len;               /* Requested length */
        // struct scatterlist sgv[UB_MAX_REQ_SG];

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

/*
 */
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 */
};

/*
 * The SCSI command tracing structure.
 */

#define SCMD_ST_HIST_SZ   8
#define SCMD_TRACE_SZ    63             /* Less than 4KB of 61-byte lines */

struct ub_scsi_cmd_trace {
        int hcur;
        unsigned int tag;
        unsigned int req_size, act_size;
        unsigned char op;
        unsigned char dir;
        unsigned char key, asc, ascq;
        char st_hst[SCMD_ST_HIST_SZ];   
};

struct ub_scsi_trace {
        int cur;
        struct ub_scsi_cmd_trace vec[SCMD_TRACE_SZ];
};

/*
 * 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 UB device instance.
 */
struct ub_dev {
        spinlock_t lock;
        int id;                         /* Number among ub's */
        atomic_t poison;                /* The USB device is disconnected */
        int openc;                      /* protected by ub_lock! */
                                        /* kref is too implicit for our taste */
        unsigned int tagcnt;
        int changed;                    /* Media was changed */
        int removable;
        int readonly;
        int first_open;                 /* Kludge. See ub_bd_open. */
        char name[8];
        struct usb_device *dev;
        struct usb_interface *intf;

        struct ub_capacity capacity; 
        struct gendisk *disk;

        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;

        /* XXX Use Ingo's mempool (once we have more than one) */
        int cmda[1];
        struct ub_scsi_cmd cmdv[1];

        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 */
        struct bulk_cb_wrap work_bcb;
        struct bulk_cs_wrap work_bcs;
        struct usb_ctrlrequest work_cr;

        struct ub_scsi_trace tr;
};

/*
 */
static void ub_cleanup(struct ub_dev *sc);
static int ub_bd_rq_fn_1(struct ub_dev *sc, struct request *rq);
static int ub_cmd_build_block(struct ub_dev *sc, struct ub_scsi_cmd *cmd,
    struct request *rq);
static int ub_cmd_build_packet(struct ub_dev *sc, struct ub_scsi_cmd *cmd,
    struct request *rq);
static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_end_rq(struct request *rq, int uptodate);
static int ub_submit_scsi(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_urb_complete(struct urb *urb, struct pt_regs *pt);
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_state_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd, int rc);
static void __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_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 int ub_sync_tur(struct ub_dev *sc);
static int ub_sync_read_cap(struct ub_dev *sc, struct ub_capacity *ret);

/*
 */
static struct usb_device_id ub_usb_ids[] = {
        // { USB_DEVICE_VER(0x0781, 0x0002, 0x0009, 0x0009) },  /* SDDR-31 */
        { USB_INTERFACE_INFO(USB_CLASS_MASS_STORAGE, US_SC_SCSI, US_PR_BULK) },
        { }
};

MODULE_DEVICE_TABLE(usb, ub_usb_ids);

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

/*
 * The SCSI command tracing procedures.
 */

static void ub_cmdtr_new(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        int n;
        struct ub_scsi_cmd_trace *t;

        if ((n = sc->tr.cur + 1) == SCMD_TRACE_SZ) n = 0;
        t = &sc->tr.vec[n];

        memset(t, 0, sizeof(struct ub_scsi_cmd_trace));
        t->tag = cmd->tag;
        t->op = cmd->cdb[0];
        t->dir = cmd->dir;
        t->req_size = cmd->len;
        t->st_hst[0] = cmd->state;

        sc->tr.cur = n;
        cmd->trace_index = n;
}

static void ub_cmdtr_state(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        int n;
        struct ub_scsi_cmd_trace *t;

        t = &sc->tr.vec[cmd->trace_index];
        if (t->tag == cmd->tag) {
                if ((n = t->hcur + 1) == SCMD_ST_HIST_SZ) n = 0;
                t->st_hst[n] = cmd->state;
                t->hcur = n;
        }
}

static void ub_cmdtr_act_len(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        struct ub_scsi_cmd_trace *t;

        t = &sc->tr.vec[cmd->trace_index];
        if (t->tag == cmd->tag)
                t->act_size = cmd->act_len;
}

static void ub_cmdtr_sense(struct ub_dev *sc, struct ub_scsi_cmd *cmd,
    unsigned char *sense)
{
        struct ub_scsi_cmd_trace *t;

        t = &sc->tr.vec[cmd->trace_index];
        if (t->tag == cmd->tag) {
                t->key = sense[2] & 0x0F;
                t->asc = sense[12];
                t->ascq = sense[13];
        }
}

static ssize_t ub_diag_show(struct device *dev, char *page)
{
        struct usb_interface *intf;
        struct ub_dev *sc;
        int cnt;
        unsigned long flags;
        int nc, nh;
        int i, j;
        struct ub_scsi_cmd_trace *t;

        intf = to_usb_interface(dev);
        sc = usb_get_intfdata(intf);
        if (sc == NULL)
                return 0;

        cnt = 0;
        spin_lock_irqsave(&sc->lock, flags);

        cnt += sprintf(page + cnt,
            "qlen %d qmax %d changed %d removable %d readonly %d\n",
            sc->cmd_queue.qlen, sc->cmd_queue.qmax,
            sc->changed, sc->removable, sc->readonly);

        if ((nc = sc->tr.cur + 1) == SCMD_TRACE_SZ) nc = 0;
        for (j = 0; j < SCMD_TRACE_SZ; j++) {
                t = &sc->tr.vec[nc];

                cnt += sprintf(page + cnt, "%08x %02x", t->tag, t->op);
                if (t->op == REQUEST_SENSE) {
                        cnt += sprintf(page + cnt, " [sense %x %02x %02x]",
                                        t->key, t->asc, t->ascq);
                } else {
                        cnt += sprintf(page + cnt, " %c", UB_DIR_CHAR(t->dir));
                        cnt += sprintf(page + cnt, " [%5d %5d]",
                                        t->req_size, t->act_size);
                }
                if ((nh = t->hcur + 1) == SCMD_ST_HIST_SZ) nh = 0;
                for (i = 0; i < SCMD_ST_HIST_SZ; i++) {
                        cnt += sprintf(page + cnt, " %s",
                                        ub_scsi_cmd_stname[(int)t->st_hst[nh]]);
                        if (++nh == SCMD_ST_HIST_SZ) nh = 0;
                }
                cnt += sprintf(page + cnt, "\n");

                if (++nc == SCMD_TRACE_SZ) nc = 0;
        }

        spin_unlock_irqrestore(&sc->lock, flags);
        return cnt;
}

static DEVICE_ATTR(diag, S_IRUGO, ub_diag_show, NULL); /* N.B. World readable */

/*
 * 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);
}

/*
 * 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)
{
        request_queue_t *q;

        /* I don't think queue can be NULL. But... Stolen from sx8.c */
        if ((q = sc->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(sc->disk);
        sc->disk = NULL;

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

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

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

static void ub_put_cmd(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        if (cmd != &sc->cmdv[0]) {
                printk(KERN_WARNING "%s: releasing a foreign cmd %p\n",
                    sc->name, cmd);
                return;
        }
        if (!sc->cmda[0]) {
                printk(KERN_WARNING "%s: releasing a free cmd\n", sc->name);
                return;
        }
        sc->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_bd_rq_fn(request_queue_t *q)
{
        struct ub_dev *sc = q->queuedata;
        struct request *rq;

        while ((rq = elv_next_request(q)) != NULL) {
                if (ub_bd_rq_fn_1(sc, rq) != 0) {
                        blk_stop_queue(q);
                        break;
                }
        }
}

static int ub_bd_rq_fn_1(struct ub_dev *sc, struct request *rq)
{
        struct ub_scsi_cmd *cmd;
        int rc;

        if (atomic_read(&sc->poison) || sc->changed) {
                blkdev_dequeue_request(rq);
                ub_end_rq(rq, 0);
                return 0;
        }

        if ((cmd = ub_get_cmd(sc)) == NULL)
                return -1;
        memset(cmd, 0, sizeof(struct ub_scsi_cmd));

        blkdev_dequeue_request(rq);

        if (blk_pc_request(rq)) {
                rc = ub_cmd_build_packet(sc, cmd, rq);
        } else {
                rc = ub_cmd_build_block(sc, cmd, rq);
        }
        if (rc != 0) {
                ub_put_cmd(sc, cmd);
                ub_end_rq(rq, 0);
                blk_start_queue(sc->disk->queue);
                return 0;
        }

        cmd->state = UB_CMDST_INIT;
        cmd->done = ub_rw_cmd_done;
        cmd->back = rq;

        cmd->tag = sc->tagcnt++;
        if ((rc = ub_submit_scsi(sc, cmd)) != 0) {
                ub_put_cmd(sc, cmd);
                ub_end_rq(rq, 0);
                blk_start_queue(sc->disk->queue);
                return 0;
        }

        return 0;
}

static int ub_cmd_build_block(struct ub_dev *sc, struct ub_scsi_cmd *cmd,
    struct request *rq)
{
        int ub_dir;
#if 0 /* We use rq->buffer for now */
        struct scatterlist *sg;
        int n_elem;
#endif
        unsigned int block, nblks;

        if (rq_data_dir(rq) == WRITE)
                ub_dir = UB_DIR_WRITE;
        else
                ub_dir = UB_DIR_READ;

        /*
         * get scatterlist from block layer
         */
#if 0 /* We use rq->buffer for now */
        sg = &cmd->sgv[0];
        n_elem = blk_rq_map_sg(q, rq, sg);
        if (n_elem <= 0) {
                ub_put_cmd(sc, cmd);
                ub_end_rq(rq, 0);
                blk_start_queue(q);
                return 0;               /* request with no s/g entries? */
        }

        if (n_elem != 1) {              /* Paranoia */
                printk(KERN_WARNING "%s: request with %d segments\n",
                    sc->name, n_elem);
                ub_put_cmd(sc, cmd);
                ub_end_rq(rq, 0);
                blk_start_queue(q);
                return 0;
        }
#endif

        /*
         * XXX Unfortunately, this check does not work. It is quite possible
         * to get bogus non-null rq->buffer if you allow sg by mistake.
         */
        if (rq->buffer == NULL) {
                /*
                 * This must not happen if we set the queue right.
                 * The block level must create bounce buffers for us.
                 */
                static int do_print = 1;
                if (do_print) {
                        printk(KERN_WARNING "%s: unmapped block request"
                            " flags 0x%lx sectors %lu\n",
                            sc->name, rq->flags, rq->nr_sectors);
                        do_print = 0;
                }
                return -1;
        }

        /*
         * 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 >> sc->capacity.bshift;
        nblks = rq->nr_sectors >> sc->capacity.bshift;

        cmd->cdb[0] = (ub_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->dir = ub_dir;
        cmd->data = rq->buffer;
        cmd->len = rq->nr_sectors * 512;

        return 0;
}

static int ub_cmd_build_packet(struct ub_dev *sc, struct ub_scsi_cmd *cmd,
    struct request *rq)
{

        if (rq->data_len != 0 && rq->data == NULL) {
                static int do_print = 1;
                if (do_print) {
                        printk(KERN_WARNING "%s: unmapped packet request"
                            " flags 0x%lx length %d\n",
                            sc->name, rq->flags, rq->data_len);
                        do_print = 0;
                }
                return -1;
        }

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

        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->data = rq->data;
        cmd->len = rq->data_len;

        return 0;
}

static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
        struct request *rq = cmd->back;
        struct gendisk *disk = sc->disk;
        request_queue_t *q = disk->queue;
        int uptodate;

        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 (cmd->error == 0)
                uptodate = 1;
        else
                uptodate = 0;

        ub_put_cmd(sc, cmd);
        ub_end_rq(rq, uptodate);
        blk_start_queue(q);
}

static void ub_end_rq(struct request *rq, int uptodate)
{
        int rc;

        rc = end_that_request_first(rq, uptodate, rq->hard_nr_sectors);
        // assert(rc == 0);
        end_that_request_last(rq);
}

/*
 * 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.
 *
 * XXX We only support Bulk for the moment.
 */
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 = 0;                   /* No multi-LUN yet */
        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);
        sc->work_urb.transfer_flags = URB_ASYNC_UNLINK;

        /* Fill what we shouldn't be filling, because usb-storage did so. */
        sc->work_urb.actual_length = 0;
        sc->work_urb.error_count = 0;
        sc->work_urb.status = 0;

        if ((rc = usb_submit_urb(&sc->work_urb, GFP_ATOMIC)) != 0) {
                /* XXX Clear stalls */
                printk("ub: cmd #%d start failed (%d)\n", cmd->tag, rc); /* P3 */
                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;
        ub_cmdtr_state(sc, 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);
        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 pt_regs *pt)
{
        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);
        del_timer(&sc->work_timer);
        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 ((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) {
                        ub_cmdtr_new(sc, cmd);
                        if ((rc = ub_scsi_cmd_start(sc, cmd)) == 0)
                                break;
                        cmd->error = rc;
                        cmd->state = UB_CMDST_DONE;
                        ub_cmdtr_state(sc, cmd);
                } else {
                        if (!ub_is_completed(&sc->work_done))
                                break;
                        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 pipe;
        int rc;

        if (atomic_read(&sc->poison)) {
                /* A little too simplistic, I feel... */
                goto Bad_End;
        }

        if (cmd->state == UB_CMDST_CLEAR) {
                if (urb->status == -EPIPE) {
                        /*
                         * STALL while clearning STALL.
                         * The control pipe clears itself - nothing to do.
                         * XXX Might try to reset the device here and retry.
                         */
                        printk(KERN_NOTICE "%s: "
                            "stall on control pipe for device %u\n",
                            sc->name, sc->dev->devnum);
                        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) {
                        /*
                         * STALL while clearning STALL.
                         * The control pipe clears itself - nothing to do.
                         * XXX Might try to reset the device here and retry.
                         */
                        printk(KERN_NOTICE "%s: "
                            "stall on control pipe for device %u\n",
                            sc->name, sc->dev->devnum);
                        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_CMD) {
                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 for device %u"
                                    " (code %d)\n",
                                    sc->name, sc->dev->devnum, rc);
                                /*
                                 * This is typically ENOMEM or some other such shit.
                                 * Retrying is pointless. Just do Bad End on it...
                                 */
                                goto Bad_End;
                        }
                        cmd->state = UB_CMDST_CLEAR;
                        ub_cmdtr_state(sc, cmd);
                        return;
                }
                if (urb->status != 0) {
                        printk("ub: cmd #%d cmd status (%d)\n", cmd->tag, urb->status); /* P3 */
                        goto Bad_End;
                }
                if (urb->actual_length != US_BULK_CB_WRAP_LEN) {
                        printk("ub: cmd #%d xferred %d\n", cmd->tag, urb->actual_length); /* P3 */
                        /* XXX Must do reset here to unconfuse the device */
                        goto Bad_End;
                }

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

                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,
                    cmd->data, cmd->len, ub_urb_complete, sc);
                sc->work_urb.transfer_flags = URB_ASYNC_UNLINK;
                sc->work_urb.actual_length = 0;
                sc->work_urb.error_count = 0;
                sc->work_urb.status = 0;

                if ((rc = usb_submit_urb(&sc->work_urb, GFP_ATOMIC)) != 0) {
                        /* XXX Clear stalls */
                        printk("ub: data #%d submit failed (%d)\n", cmd->tag, rc); /* P3 */
                        ub_complete(&sc->work_done);
                        ub_state_done(sc, cmd, rc);
                        return;
                }

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

                cmd->state = UB_CMDST_DATA;
                ub_cmdtr_state(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 for device %u"
                                    " (code %d)\n",
                                    sc->name, sc->dev->devnum, rc);
                                /*
                                 * This is typically ENOMEM or some other such shit.
                                 * Retrying is pointless. Just do Bad End on it...
                                 */
                                goto Bad_End;
                        }
                        cmd->state = UB_CMDST_CLR2STS;
                        ub_cmdtr_state(sc, cmd);
                        return;
                }
                if (urb->status == -EOVERFLOW) {
                        /*
                         * A babble? Failure, but we must transfer CSW now.
                         */
                        cmd->error = -EOVERFLOW;        /* A cheap trick... */
                } else {
                        if (urb->status != 0)
                                goto Bad_End;
                }

                cmd->act_len = urb->actual_length;
                ub_cmdtr_act_len(sc, cmd);

                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 for device %u"
                                    " (code %d)\n",
                                    sc->name, sc->dev->devnum, rc);
                                /*
                                 * This is typically ENOMEM or some other such shit.
                                 * Retrying is pointless. Just do Bad End on it...
                                 */
                                goto Bad_End;
                        }
                        cmd->state = UB_CMDST_CLEAR;
                        ub_cmdtr_state(sc, cmd);
                        return;
                }
                if (urb->status != 0)
                        goto Bad_End;

                if (urb->actual_length == 0) {
                        /*
                         * Some broken devices add unnecessary zero-length
                         * packets to the end of their data transfers.
                         * Such packets show up as 0-length CSWs. If we
                         * encounter such a thing, try to read the CSW again.
                         */
                        if (++cmd->stat_count >= 4) {
                                printk(KERN_NOTICE "%s: "
                                    "unable to get CSW on device %u\n",
                                    sc->name, sc->dev->devnum);
                                goto Bad_End;
                        }
                        __ub_state_stat(sc, cmd);
                        return;
                }

                /*
                 * Check the returned Bulk protocol status.
                 */

                bcs = &sc->work_bcs;
                rc = le32_to_cpu(bcs->Residue);
                if (rc != cmd->len - cmd->act_len) {
                        /*
                         * It is all right to transfer less, the caller has
                         * to check. But it's not all right if the device
                         * counts disagree with our counts.
                         */
                        /* P3 */ printk("%s: resid %d len %d act %d\n",
                            sc->name, rc, cmd->len, cmd->act_len);
                        goto Bad_End;
                }

#if 0
                if (bcs->Signature != cpu_to_le32(US_BULK_CS_SIGN) &&
                    bcs->Signature != cpu_to_le32(US_BULK_CS_OLYMPUS_SIGN)) {
                        /* Windows ignores signatures, so do we. */
                }
#endif

                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.
                         */
                        if (++cmd->stat_count >= 4) {
                                printk(KERN_NOTICE "%s: "
                                    "tag mismatch orig 0x%x reply 0x%x "
                                    "on device %u\n",
                                    sc->name, cmd->tag, bcs->Tag,
                                    sc->dev->devnum);
                                goto Bad_End;
                        }
                        __ub_state_stat(sc, cmd);
                        return;
                }

                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:
                        /* XXX We must reset the transport here */
                        /* P3 */ printk("%s: status PHASE\n", sc->name);
                        goto Bad_End;
                default:
                        printk(KERN_INFO "%s: unknown CSW status 0x%x\n",
                            sc->name, bcs->Status);
                        goto Bad_End;
                }

                /* Not zeroing error to preserve a babble indicator */
                cmd->state = UB_CMDST_DONE;
                ub_cmdtr_state(sc, cmd);
                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 on device %u\n",
                    sc->name, cmd->state, sc->dev->devnum);
                goto Bad_End;
        }
        return;

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

/*
 * 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_cmdtr_state(sc, cmd);
        ub_cmdq_pop(sc);
        (*cmd->done)(sc, cmd);
}

/*
 * Factorization helper for the command state machine:
 * Submit a CSW read.
 */
static void __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);
        sc->work_urb.transfer_flags = URB_ASYNC_UNLINK;
        sc->work_urb.actual_length = 0;
        sc->work_urb.error_count = 0;
        sc->work_urb.status = 0;

        if ((rc = usb_submit_urb(&sc->work_urb, GFP_ATOMIC)) != 0) {
                /* XXX Clear stalls */
                printk("%s: CSW #%d submit failed (%d)\n", sc->name, cmd->tag, rc); /* P3 */
                ub_complete(&sc->work_done);
                ub_state_done(sc, cmd, rc);
                return;
        }

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

/*
 * 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)
{
        __ub_state_stat(sc, cmd);

        cmd->stat_count = 0;
        cmd->state = UB_CMDST_STAT;
        ub_cmdtr_state(sc, cmd);
}

/*
 * 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;
        int rc;

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

        scmd = &sc->top_rqs_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->data = sc->top_sense;
        scmd->len = UB_SENSE_SIZE;
        scmd->done = ub_top_sense_done;
        scmd->back = cmd;

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

        cmd->state = UB_CMDST_SENSE;
        ub_cmdtr_state(sc, cmd);

        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);
        sc->work_urb.transfer_flags = URB_ASYNC_UNLINK;
        sc->work_urb.actual_length = 0;
        sc->work_urb.error_count = 0;
        sc->work_urb.status = 0;

        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 = scmd->data;
        struct ub_scsi_cmd *cmd;

        /*
         * Ignoring scmd->act_len, because the buffer was pre-zeroed.
         */
        ub_cmdtr_sense(sc, scmd, sense);

        /*
         * 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 on device %u\n",
                    sc->name, cmd->tag, sc->dev->devnum);
                return;
        }
        if (cmd->state != UB_CMDST_SENSE) {
                printk(KERN_WARNING "%s: "
                    "sense done with bad cmd state %d on device %u\n",
                    sc->name, cmd->state, sc->dev->devnum);
                return;
        }

        cmd->key = sense[2] & 0x0F;
        cmd->asc = sense[12];
        cmd->ascq = sense[13];

        ub_scsi_urb_compl(sc, cmd);
}

#if 0
/* Determine what the maximum LUN supported is */
int usb_stor_Bulk_max_lun(struct us_data *us)
{
        int result;

        /* issue the command */
        result = usb_stor_control_msg(us, us->recv_ctrl_pipe,
                                 US_BULK_GET_MAX_LUN, 
                                 USB_DIR_IN | USB_TYPE_CLASS | 
                                 USB_RECIP_INTERFACE,
                                 0, us->ifnum, us->iobuf, 1, HZ);

        /* 
         * Some devices (i.e. Iomega Zip100) need this -- apparently
         * the bulk pipes get STALLed when the GetMaxLUN request is
         * processed.   This is, in theory, harmless to all other devices
         * (regardless of if they stall or not).
         */
        if (result < 0) {
                usb_stor_clear_halt(us, us->recv_bulk_pipe);
                usb_stor_clear_halt(us, us->send_bulk_pipe);
        }

        US_DEBUGP("GetMaxLUN command result is %d, data is %d\n", 
                  result, us->iobuf[0]);

        /* if we have a successful request, return the result */
        if (result == 1)
                return us->iobuf[0];

        /* return the default -- no LUNs */
        return 0;
}
#endif

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

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

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

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

        if (ub_sync_read_cap(sc, &sc->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, &sc->capacity) != 0) {
                        sc->capacity.nsec = 0;
                        sc->capacity.bsize = 512;
                        sc->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_dev *sc;
        unsigned long flags;
        int rc;

        if ((sc = disk->private_data) == NULL)
                return -ENXIO;
        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);

        /*
         * This is a workaround for a specific problem in our block layer.
         * In 2.6.9, register_disk duplicates the code from rescan_partitions.
         * However, if we do add_disk with a device which persistently reports
         * a changed media, add_disk calls register_disk, which does do_open,
         * which will call rescan_paritions for changed media. After that,
         * register_disk attempts to do it all again and causes double kobject
         * registration and a eventually an oops on module removal.
         *
         * The bottom line is, Al Viro says that we should not allow
         * bdev->bd_invalidated to be set when doing add_disk no matter what.
         */
        if (sc->first_open) {
                if (sc->changed) {
                        sc->first_open = 0;
                        rc = -ENOMEDIUM;
                        goto err_open;
                }
        }

        if (sc->removable || sc->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 (sc->removable && sc->changed && !(filp->f_flags & O_NDELAY)) {
                rc = -ENOMEDIUM;
                goto err_open;
        }

        if (sc->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_dev *sc = disk->private_data;

        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)
{
        struct gendisk *disk = inode->i_bdev->bd_disk;
        void __user *usermem = (void __user *) arg;

        return scsi_cmd_ioctl(filp, disk, cmd, usermem);
}

/*
 * This is called once a new disk was seen by the block layer or by ub_probe().
 * 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_dev *sc = disk->private_data;

        ub_revalidate(sc);
        /* This is pretty much a long term P3 */
        if (!atomic_read(&sc->poison)) {                /* Cover sc->dev */
                printk(KERN_INFO "%s: device %u capacity nsec %ld bsize %u\n",
                    sc->name, sc->dev->devnum,
                    sc->capacity.nsec, sc->capacity.bsize);
        }

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

        if (!sc->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(sc) != 0) {
                sc->changed = 1;
                return 1;
        }

        return sc->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_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 = kmalloc(ALLOC_SIZE, GFP_KERNEL)) == NULL)
                goto err_alloc;
        memset(cmd, 0, ALLOC_SIZE);

        cmd->cdb[0] = TEST_UNIT_READY;
        cmd->cdb_len = 6;
        cmd->dir = UB_DIR_NONE;
        cmd->state = UB_CMDST_INIT;
        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) {
                printk("ub: testing ready: submit error (%d)\n", rc); /* P3 */
                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_capacity *ret)
{
        struct ub_scsi_cmd *cmd;
        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 = kmalloc(ALLOC_SIZE, GFP_KERNEL)) == NULL)
                goto err_alloc;
        memset(cmd, 0, ALLOC_SIZE);
        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->data = p;
        cmd->len = 8;
        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) {
                printk("ub: reading capacity: submit error (%d)\n", rc); /* P3 */
                goto err_submit;
        }

        wait_for_completion(&compl);

        if (cmd->error != 0) {
                printk("ub: reading capacity: error %d\n", cmd->error); /* P3 */
                rc = -EIO;
                goto err_read;
        }
        if (cmd->act_len != 8) {
                printk("ub: reading capacity: size %d\n", cmd->act_len); /* P3 */
                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:
                printk("ub: Bad sector size %u\n", bsize); /* P3 */
                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 pt_regs *pt)
{
        struct completion *cop = urb->context;
        complete(cop);
}

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

/*
 * Clear initial stalls.
 */
static int ub_probe_clear_stall(struct ub_dev *sc, int stalled_pipe)
{
        int endp;
        struct usb_ctrlrequest *cr;
        struct completion compl;
        struct timer_list timer;
        int rc;

        init_completion(&compl);

        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);

        usb_fill_control_urb(&sc->work_urb, sc->dev, sc->send_ctrl_pipe,
            (unsigned char*) cr, NULL, 0, ub_probe_urb_complete, &compl);
        sc->work_urb.transfer_flags = 0;
        sc->work_urb.actual_length = 0;
        sc->work_urb.error_count = 0;
        sc->work_urb.status = 0;

        if ((rc = usb_submit_urb(&sc->work_urb, GFP_KERNEL)) != 0) {
                printk(KERN_WARNING
                     "%s: Unable to submit a probe clear (%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);

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

        return 0;
}

/*
 * Get the pipe settings.
 */
static int ub_get_pipes(struct ub_dev *sc, struct usb_device *dev,
    struct usb_interface *intf)
{
        struct usb_host_interface *altsetting = intf->cur_altsetting;
        struct usb_endpoint_descriptor *ep_in = NULL;
        struct usb_endpoint_descriptor *ep_out = NULL;
        struct usb_endpoint_descriptor *ep;
        int i;

        /*
         * Find the endpoints we need.
         * We are expecting a minimum of 2 endpoints - in and out (bulk).
         * We will ignore any others.
         */
        for (i = 0; i < altsetting->desc.bNumEndpoints; i++) {
                ep = &altsetting->endpoint[i].desc;

                /* Is it a BULK endpoint? */
                if ((ep->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK)
                                == USB_ENDPOINT_XFER_BULK) {
                        /* BULK in or out? */
                        if (ep->bEndpointAddress & USB_DIR_IN)
                                ep_in = ep;
                        else
                                ep_out = ep;
                }
        }

        if (ep_in == NULL || ep_out == NULL) {
                printk(KERN_NOTICE "%s: device %u failed endpoint check\n",
                    sc->name, sc->dev->devnum);
                return -EIO;
        }

        /* Calculate and store the pipe values */
        sc->send_ctrl_pipe = usb_sndctrlpipe(dev, 0);
        sc->recv_ctrl_pipe = usb_rcvctrlpipe(dev, 0);
        sc->send_bulk_pipe = usb_sndbulkpipe(dev,
                ep_out->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK);
        sc->recv_bulk_pipe = usb_rcvbulkpipe(dev, 
                ep_in->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK);

        return 0;
}

/*
 * Probing is done in the process context, which allows us to cheat
 * and not to build a state machine for the discovery.
 */
static int ub_probe(struct usb_interface *intf,
    const struct usb_device_id *dev_id)
{
        struct ub_dev *sc;
        request_queue_t *q;
        struct gendisk *disk;
        int rc;
        int i;

        rc = -ENOMEM;
        if ((sc = kmalloc(sizeof(struct ub_dev), GFP_KERNEL)) == NULL)
                goto err_core;
        memset(sc, 0, sizeof(struct ub_dev));
        spin_lock_init(&sc->lock);
        usb_init_urb(&sc->work_urb);
        tasklet_init(&sc->tasklet, ub_scsi_action, (unsigned long)sc);
        atomic_set(&sc->poison, 0);

        init_timer(&sc->work_timer);
        sc->work_timer.data = (unsigned long) sc;
        sc->work_timer.function = ub_urb_timeout;

        ub_init_completion(&sc->work_done);
        sc->work_done.done = 1;         /* A little yuk, but oh well... */

        rc = -ENOSR;
        if ((sc->id = ub_id_get()) == -1)
                goto err_id;
        snprintf(sc->name, 8, DRV_NAME "%c", sc->id + 'a');

        sc->dev = interface_to_usbdev(intf);
        sc->intf = intf;
        // sc->ifnum = intf->cur_altsetting->desc.bInterfaceNumber;

        usb_set_intfdata(intf, sc);
        usb_get_dev(sc->dev);
        // usb_get_intf(sc->intf);      /* Do we need this? */

        /* XXX Verify that we can handle the device (from descriptors) */

        ub_get_pipes(sc, sc->dev, intf);

        if (device_create_file(&sc->intf->dev, &dev_attr_diag) != 0)
                goto err_diag;

        /*
         * At this point, all USB initialization is done, do upper layer.
         * We really hate halfway initialized structures, so from the
         * invariants perspective, this ub_dev is fully constructed at
         * this point.
         */

        /*
         * This is needed to clear toggles. It is a problem only if we do
         * `rmmod ub && modprobe ub` without disconnects, but we like that.
         */
        ub_probe_clear_stall(sc, sc->recv_bulk_pipe);
        ub_probe_clear_stall(sc, sc->send_bulk_pipe);

        /*
         * The way this is used by the startup code is a little specific.
         * A SCSI check causes a USB stall. Our common case code sees it
         * and clears the check, after which the device is ready for use.
         * But if a check was not present, any command other than
         * TEST_UNIT_READY ends with a lockup (including REQUEST_SENSE).
         *
         * If we neglect to clear the SCSI check, the first real command fails
         * (which is the capacity readout). We clear that and retry, but why
         * causing spurious retries for no reason.
         *
         * Revalidation may start with its own TEST_UNIT_READY, but that one
         * has to succeed, so we clear checks with an additional one here.
         * In any case it's not our business how revaliadation is implemented.
         */
        for (i = 0; i < 3; i++) {       /* Retries for benh's key */
                if ((rc = ub_sync_tur(sc)) <= 0) break;
                if (rc != 0x6) break;
                msleep(10);
        }

        sc->removable = 1;              /* XXX Query this from the device */
        sc->changed = 1;                /* ub_revalidate clears only */
        sc->first_open = 1;

        ub_revalidate(sc);
        /* This is pretty much a long term P3 */
        printk(KERN_INFO "%s: device %u capacity nsec %ld bsize %u\n",
            sc->name, sc->dev->devnum, sc->capacity.nsec, sc->capacity.bsize);

        /*
         * Just one disk per sc currently, but maybe more.
         */
        rc = -ENOMEM;
        if ((disk = alloc_disk(UB_MINORS_PER_MAJOR)) == NULL)
                goto err_diskalloc;

        sc->disk = disk;
        sprintf(disk->disk_name, DRV_NAME "%c", sc->id + 'a');
        sprintf(disk->devfs_name, DEVFS_NAME "/%c", sc->id + 'a');
        disk->major = UB_MAJOR;
        disk->first_minor = sc->id * UB_MINORS_PER_MAJOR;
        disk->fops = &ub_bd_fops;
        disk->private_data = sc;
        disk->driverfs_dev = &intf->dev;

        rc = -ENOMEM;
        if ((q = blk_init_queue(ub_bd_rq_fn, &sc->lock)) == NULL)
                goto err_blkqinit;

        disk->queue = q;

        // blk_queue_bounce_limit(q, hba[i]->pdev->dma_mask);
        blk_queue_max_hw_segments(q, UB_MAX_REQ_SG);
        blk_queue_max_phys_segments(q, UB_MAX_REQ_SG);
        // blk_queue_segment_boundary(q, CARM_SG_BOUNDARY);
        blk_queue_max_sectors(q, UB_MAX_SECTORS);
        blk_queue_hardsect_size(q, sc->capacity.bsize);

        /*
         * This is a serious infraction, caused by a deficiency in the
         * USB sg interface (usb_sg_wait()). We plan to remove this once
         * we get mileage on the driver and can justify a change to USB API.
         * See blk_queue_bounce_limit() to understand this part.
         *
         * XXX And I still need to be aware of the DMA mask in the HC.
         */
        q->bounce_pfn = blk_max_low_pfn;
        q->bounce_gfp = GFP_NOIO;

        q->queuedata = sc;

        set_capacity(disk, sc->capacity.nsec);
        if (sc->removable)
                disk->flags |= GENHD_FL_REMOVABLE;

        add_disk(disk);

        return 0;

err_blkqinit:
        put_disk(disk);
err_diskalloc:
        device_remove_file(&sc->intf->dev, &dev_attr_diag);
err_diag:
        usb_set_intfdata(intf, NULL);
        // usb_put_intf(sc->intf);
        usb_put_dev(sc->dev);
        ub_id_put(sc->id);
err_id:
        kfree(sc);
err_core:
        return rc;
}

static void ub_disconnect(struct usb_interface *intf)
{
        struct ub_dev *sc = usb_get_intfdata(intf);
        struct gendisk *disk = sc->disk;
        unsigned long flags;

        /*
         * Prevent ub_bd_release from pulling the rug from under us.
         * XXX This is starting to look like a kref.
         * XXX Why not to take this ref at probe time?
         */
        spin_lock_irqsave(&ub_lock, flags);
        sc->openc++;
        spin_unlock_irqrestore(&ub_lock, flags);

        /*
         * Fence stall clearnings, operations triggered by unlinkings and so on.
         * We do not attempt to unlink any URBs, because we do not trust the
         * unlink paths in HC drivers. Also, we get -84 upon disconnect anyway.
         */
        atomic_set(&sc->poison, 1);

        /*
         * Blow away queued commands.
         *
         * Actually, this never works, because before we get here
         * the HCD terminates outstanding URB(s). It causes our
         * SCSI command queue to advance, commands fail to submit,
         * and the whole queue drains. So, we just use this code to
         * print warnings.
         */
        spin_lock_irqsave(&sc->lock, flags);
        {
                struct ub_scsi_cmd *cmd;
                int cnt = 0;
                while ((cmd = ub_cmdq_pop(sc)) != NULL) {
                        cmd->error = -ENOTCONN;
                        cmd->state = UB_CMDST_DONE;
                        ub_cmdtr_state(sc, cmd);
                        ub_cmdq_pop(sc);
                        (*cmd->done)(sc, cmd);
                        cnt++;
                }
                if (cnt != 0) {
                        printk(KERN_WARNING "%s: "
                            "%d was queued after shutdown\n", sc->name, cnt);
                }
        }
        spin_unlock_irqrestore(&sc->lock, flags);

        /*
         * Unregister the upper layer.
         */
        if (disk->flags & GENHD_FL_UP)
                del_gendisk(disk);
        /*
         * I wish I could do:
         *    set_bit(QUEUE_FLAG_DEAD, &q->queue_flags);
         * As it is, we rely on our internal poisoning and let
         * the upper levels to spin furiously failing all the I/O.
         */

        /*
         * Taking a lock on a structure which is about to be freed
         * is very nonsensual. Here it is largely a way to do a debug freeze,
         * and a bracket which shows where the nonsensual code segment ends.
         *
         * Testing for -EINPROGRESS is always a bug, so we are bending
         * the rules a little.
         */
        spin_lock_irqsave(&sc->lock, flags);
        if (sc->work_urb.status == -EINPROGRESS) {      /* janitors: ignore */
                printk(KERN_WARNING "%s: "
                    "URB is active after disconnect\n", sc->name);
        }
        spin_unlock_irqrestore(&sc->lock, flags);

        /*
         * There is virtually no chance that other CPU runs times so long
         * after ub_urb_complete should have called del_timer, but only if HCD
         * didn't forget to deliver a callback on unlink.
         */
        del_timer_sync(&sc->work_timer);

        /*
         * At this point there must be no commands coming from anyone
         * and no URBs left in transit.
         */

        device_remove_file(&sc->intf->dev, &dev_attr_diag);
        usb_set_intfdata(intf, NULL);
        // usb_put_intf(sc->intf);
        sc->intf = NULL;
        usb_put_dev(sc->dev);
        sc->dev = NULL;

        ub_put(sc);
}

static struct usb_driver ub_driver = {
        .owner =        THIS_MODULE,
        .name =         "ub",
        .probe =        ub_probe,
        .disconnect =   ub_disconnect,
        .id_table =     ub_usb_ids,
};

static int __init ub_init(void)
{
        int rc;

        /* P3 */ printk("ub: sizeof ub_scsi_cmd %zu ub_dev %zu\n",
                        sizeof(struct ub_scsi_cmd), sizeof(struct ub_dev));

        if ((rc = register_blkdev(UB_MAJOR, DRV_NAME)) != 0)
                goto err_regblkdev;
        devfs_mk_dir(DEVFS_NAME);

        if ((rc = usb_register(&ub_driver)) != 0)
                goto err_register;

        return 0;

err_register:
        devfs_remove(DEVFS_NAME);
        unregister_blkdev(UB_MAJOR, DRV_NAME);
err_regblkdev:
        return rc;
}

static void __exit ub_exit(void)
{
        usb_deregister(&ub_driver);

        devfs_remove(DEVFS_NAME);
        unregister_blkdev(UB_MAJOR, DRV_NAME);
}

module_init(ub_init);
module_exit(ub_exit);

MODULE_LICENSE("GPL");