USB: Add UAS driver

USB Attached SCSI is a new protocol specified jointly by the SCSI T10
committee and the USB Implementors Forum.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
[mina86@mina86.com: updated to use new USB_ prefix]
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

4 files changed, 773 insertions, 0 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index f2a2b8e647c5..8dac57f53d87 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5934,6 +5934,14 @@ S:	Maintained
 F:      Documentation/usb/acm.txt
 F:      drivers/usb/class/cdc-acm.*
 
+USB ATTACHED SCSI
+M:      Matthew Wilcox <willy@linux.intel.com>
+M:      Sarah Sharp <sarah.a.sharp@linux.intel.com>
+L:      linux-usb@vger.kernel.org
+L:      linux-scsi@vger.kernel.org
+S:      Supported
+F:      drivers/usb/storage/uas.c
+
 USB BLOCK DRIVER (UB ub)
 M:      Pete Zaitcev <zaitcev@redhat.com>
 L:      linux-usb@vger.kernel.org
diff --git a/drivers/usb/storage/Kconfig b/drivers/usb/storage/Kconfig
index 8a372bac0e43..f2767cf2e229 100644
--- a/drivers/usb/storage/Kconfig
+++ b/drivers/usb/storage/Kconfig
@@ -172,6 +172,19 @@ config USB_STORAGE_CYPRESS_ATACB
 
           If this driver is compiled as a module, it will be named ums-cypress.
 
+config USB_UAS
+        tristate "USB Attached SCSI"
+        depends on USB && SCSI
+        help
+          The USB Attached SCSI protocol is supported by some USB
+          storage devices.  It permits higher performance by supporting
+          multiple outstanding commands.
+
+          If you don't know whether you have a UAS device, it is safe to
+          say 'Y' or 'M' here and the kernel will use the right driver.
+
+          If you compile this driver as a module, it will be named uas.
+
 config USB_LIBUSUAL
         bool "The shared table of common (or usual) storage devices"
         depends on USB
diff --git a/drivers/usb/storage/Makefile b/drivers/usb/storage/Makefile
index ef7e5a8ceab5..0332aa5df24f 100644
--- a/drivers/usb/storage/Makefile
+++ b/drivers/usb/storage/Makefile
@@ -7,6 +7,7 @@
 
 EXTRA_CFLAGS    := -Idrivers/scsi
 
+obj-$(CONFIG_USB_UAS)           += uas.o
 obj-$(CONFIG_USB_STORAGE)       += usb-storage.o
 
 usb-storage-obj-$(CONFIG_USB_STORAGE_DEBUG)     += debug.o
diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c
new file mode 100644
index 000000000000..2054b1e25a65
--- /dev/null
+++ b/drivers/usb/storage/uas.c
@@ -0,0 +1,751 @@
+/*
+ * USB Attached SCSI
+ * Note that this is not the same as the USB Mass Storage driver
+ *
+ * Copyright Matthew Wilcox for Intel Corp, 2010
+ * Copyright Sarah Sharp for Intel Corp, 2010
+ *
+ * Distributed under the terms of the GNU GPL, version two.
+ */
+
+#include <linux/blkdev.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/usb.h>
+#include <linux/usb/storage.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_dbg.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_host.h>
+#include <scsi/scsi_tcq.h>
+
+/* Common header for all IUs */
+struct iu {
+        __u8 iu_id;
+        __u8 rsvd1;
+        __be16 tag;
+};
+
+enum {
+        IU_ID_COMMAND           = 0x01,
+        IU_ID_STATUS            = 0x03,
+        IU_ID_RESPONSE          = 0x04,
+        IU_ID_TASK_MGMT         = 0x05,
+        IU_ID_READ_READY        = 0x06,
+        IU_ID_WRITE_READY       = 0x07,
+};
+
+struct command_iu {
+        __u8 iu_id;
+        __u8 rsvd1;
+        __be16 tag;
+        __u8 prio_attr;
+        __u8 rsvd5;
+        __u8 len;
+        __u8 rsvd7;
+        struct scsi_lun lun;
+        __u8 cdb[16];   /* XXX: Overflow-checking tools may misunderstand */
+};
+
+struct sense_iu {
+        __u8 iu_id;
+        __u8 rsvd1;
+        __be16 tag;
+        __be16 status_qual;
+        __u8 status;
+        __u8 service_response;
+        __u8 rsvd8[6];
+        __be16 len;
+        __u8 sense[SCSI_SENSE_BUFFERSIZE];
+};
+
+/*
+ * The r00-r01c specs define this version of the SENSE IU data structure.
+ * It's still in use by several different firmware releases.
+ */
+struct sense_iu_old {
+        __u8 iu_id;
+        __u8 rsvd1;
+        __be16 tag;
+        __be16 len;
+        __u8 status;
+        __u8 service_response;
+        __u8 sense[SCSI_SENSE_BUFFERSIZE];
+};
+
+enum {
+        CMD_PIPE_ID             = 1,
+        STATUS_PIPE_ID          = 2,
+        DATA_IN_PIPE_ID         = 3,
+        DATA_OUT_PIPE_ID        = 4,
+
+        UAS_SIMPLE_TAG          = 0,
+        UAS_HEAD_TAG            = 1,
+        UAS_ORDERED_TAG         = 2,
+        UAS_ACA                 = 4,
+};
+
+struct uas_dev_info {
+        struct usb_interface *intf;
+        struct usb_device *udev;
+        int qdepth;
+        unsigned cmd_pipe, status_pipe, data_in_pipe, data_out_pipe;
+        unsigned use_streams:1;
+        unsigned uas_sense_old:1;
+};
+
+enum {
+        ALLOC_SENSE_URB         = (1 << 0),
+        SUBMIT_SENSE_URB        = (1 << 1),
+        ALLOC_DATA_IN_URB       = (1 << 2),
+        SUBMIT_DATA_IN_URB      = (1 << 3),
+        ALLOC_DATA_OUT_URB      = (1 << 4),
+        SUBMIT_DATA_OUT_URB     = (1 << 5),
+        ALLOC_CMD_URB           = (1 << 6),
+        SUBMIT_CMD_URB          = (1 << 7),
+};
+
+/* Overrides scsi_pointer */
+struct uas_cmd_info {
+        unsigned int state;
+        unsigned int stream;
+        struct urb *cmd_urb;
+        struct urb *sense_urb;
+        struct urb *data_in_urb;
+        struct urb *data_out_urb;
+        struct list_head list;
+};
+
+/* I hate forward declarations, but I actually have a loop */
+static int uas_submit_urbs(struct scsi_cmnd *cmnd,
+                                struct uas_dev_info *devinfo, gfp_t gfp);
+
+static DEFINE_SPINLOCK(uas_work_lock);
+static LIST_HEAD(uas_work_list);
+
+static void uas_do_work(struct work_struct *work)
+{
+        struct uas_cmd_info *cmdinfo;
+        struct list_head list;
+
+        spin_lock_irq(&uas_work_lock);
+        list_replace_init(&uas_work_list, &list);
+        spin_unlock_irq(&uas_work_lock);
+
+        list_for_each_entry(cmdinfo, &list, list) {
+                struct scsi_pointer *scp = (void *)cmdinfo;
+                struct scsi_cmnd *cmnd = container_of(scp,
+                                                        struct scsi_cmnd, SCp);
+                uas_submit_urbs(cmnd, cmnd->device->hostdata, GFP_KERNEL);
+        }
+}
+
+static DECLARE_WORK(uas_work, uas_do_work);
+
+static void uas_sense(struct urb *urb, struct scsi_cmnd *cmnd)
+{
+        struct sense_iu *sense_iu = urb->transfer_buffer;
+        struct scsi_device *sdev = cmnd->device;
+
+        if (urb->actual_length > 16) {
+                unsigned len = be16_to_cpup(&sense_iu->len);
+                if (len + 16 != urb->actual_length) {
+                        int newlen = min(len + 16, urb->actual_length) - 16;
+                        if (newlen < 0)
+                                newlen = 0;
+                        sdev_printk(KERN_INFO, sdev, "%s: urb length %d "
+                                "disagrees with IU sense data length %d, "
+                                "using %d bytes of sense data\n", __func__,
+                                        urb->actual_length, len, newlen);
+                        len = newlen;
+                }
+                memcpy(cmnd->sense_buffer, sense_iu->sense, len);
+        }
+
+        cmnd->result = sense_iu->status;
+        if (sdev->current_cmnd)
+                sdev->current_cmnd = NULL;
+        cmnd->scsi_done(cmnd);
+        usb_free_urb(urb);
+}
+
+static void uas_sense_old(struct urb *urb, struct scsi_cmnd *cmnd)
+{
+        struct sense_iu_old *sense_iu = urb->transfer_buffer;
+        struct scsi_device *sdev = cmnd->device;
+
+        if (urb->actual_length > 8) {
+                unsigned len = be16_to_cpup(&sense_iu->len) - 2;
+                if (len + 8 != urb->actual_length) {
+                        int newlen = min(len + 8, urb->actual_length) - 8;
+                        if (newlen < 0)
+                                newlen = 0;
+                        sdev_printk(KERN_INFO, sdev, "%s: urb length %d "
+                                "disagrees with IU sense data length %d, "
+                                "using %d bytes of sense data\n", __func__,
+                                        urb->actual_length, len, newlen);
+                        len = newlen;
+                }
+                memcpy(cmnd->sense_buffer, sense_iu->sense, len);
+        }
+
+        cmnd->result = sense_iu->status;
+        if (sdev->current_cmnd)
+                sdev->current_cmnd = NULL;
+        cmnd->scsi_done(cmnd);
+        usb_free_urb(urb);
+}
+
+static void uas_xfer_data(struct urb *urb, struct scsi_cmnd *cmnd,
+                                                        unsigned direction)
+{
+        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
+        int err;
+
+        cmdinfo->state = direction | SUBMIT_SENSE_URB;
+        err = uas_submit_urbs(cmnd, cmnd->device->hostdata, GFP_ATOMIC);
+        if (err) {
+                spin_lock(&uas_work_lock);
+                list_add_tail(&cmdinfo->list, &uas_work_list);
+                spin_unlock(&uas_work_lock);
+                schedule_work(&uas_work);
+        }
+}
+
+static void uas_stat_cmplt(struct urb *urb)
+{
+        struct iu *iu = urb->transfer_buffer;
+        struct scsi_device *sdev = urb->context;
+        struct uas_dev_info *devinfo = sdev->hostdata;
+        struct scsi_cmnd *cmnd;
+        u16 tag;
+
+        if (urb->status) {
+                dev_err(&urb->dev->dev, "URB BAD STATUS %d\n", urb->status);
+                usb_free_urb(urb);
+                return;
+        }
+
+        tag = be16_to_cpup(&iu->tag) - 1;
+        if (sdev->current_cmnd)
+                cmnd = sdev->current_cmnd;
+        else
+                cmnd = scsi_find_tag(sdev, tag);
+        if (!cmnd)
+                return;
+
+        switch (iu->iu_id) {
+        case IU_ID_STATUS:
+                if (urb->actual_length < 16)
+                        devinfo->uas_sense_old = 1;
+                if (devinfo->uas_sense_old)
+                        uas_sense_old(urb, cmnd);
+                else
+                        uas_sense(urb, cmnd);
+                break;
+        case IU_ID_READ_READY:
+                uas_xfer_data(urb, cmnd, SUBMIT_DATA_IN_URB);
+                break;
+        case IU_ID_WRITE_READY:
+                uas_xfer_data(urb, cmnd, SUBMIT_DATA_OUT_URB);
+                break;
+        default:
+                scmd_printk(KERN_ERR, cmnd,
+                        "Bogus IU (%d) received on status pipe\n", iu->iu_id);
+        }
+}
+
+static void uas_data_cmplt(struct urb *urb)
+{
+        struct scsi_data_buffer *sdb = urb->context;
+        sdb->resid = sdb->length - urb->actual_length;
+        usb_free_urb(urb);
+}
+
+static struct urb *uas_alloc_data_urb(struct uas_dev_info *devinfo, gfp_t gfp,
+                                unsigned int pipe, u16 stream_id,
+                                struct scsi_data_buffer *sdb,
+                                enum dma_data_direction dir)
+{
+        struct usb_device *udev = devinfo->udev;
+        struct urb *urb = usb_alloc_urb(0, gfp);
+
+        if (!urb)
+                goto out;
+        usb_fill_bulk_urb(urb, udev, pipe, NULL, sdb->length, uas_data_cmplt,
+                                                                        sdb);
+        if (devinfo->use_streams)
+                urb->stream_id = stream_id;
+        urb->num_sgs = udev->bus->sg_tablesize ? sdb->table.nents : 0;
+        urb->sg = sdb->table.sgl;
+ out:
+        return urb;
+}
+
+static struct urb *uas_alloc_sense_urb(struct uas_dev_info *devinfo, gfp_t gfp,
+                                        struct scsi_cmnd *cmnd, u16 stream_id)
+{
+        struct usb_device *udev = devinfo->udev;
+        struct urb *urb = usb_alloc_urb(0, gfp);
+        struct sense_iu *iu;
+
+        if (!urb)
+                goto out;
+
+        iu = kmalloc(sizeof(*iu), gfp);
+        if (!iu)
+                goto free;
+
+        usb_fill_bulk_urb(urb, udev, devinfo->status_pipe, iu, sizeof(*iu),
+                                                uas_stat_cmplt, cmnd->device);
+        urb->stream_id = stream_id;
+        urb->transfer_flags |= URB_FREE_BUFFER;
+ out:
+        return urb;
+ free:
+        usb_free_urb(urb);
+        return NULL;
+}
+
+static struct urb *uas_alloc_cmd_urb(struct uas_dev_info *devinfo, gfp_t gfp,
+                                        struct scsi_cmnd *cmnd, u16 stream_id)
+{
+        struct usb_device *udev = devinfo->udev;
+        struct scsi_device *sdev = cmnd->device;
+        struct urb *urb = usb_alloc_urb(0, gfp);
+        struct command_iu *iu;
+        int len;
+
+        if (!urb)
+                goto out;
+
+        len = cmnd->cmd_len - 16;
+        if (len < 0)
+                len = 0;
+        len = ALIGN(len, 4);
+        iu = kmalloc(sizeof(*iu) + len, gfp);
+        if (!iu)
+                goto free;
+
+        iu->iu_id = IU_ID_COMMAND;
+        iu->tag = cpu_to_be16(stream_id);
+        if (sdev->ordered_tags && (cmnd->request->cmd_flags & REQ_HARDBARRIER))
+                iu->prio_attr = UAS_ORDERED_TAG;
+        else
+                iu->prio_attr = UAS_SIMPLE_TAG;
+        iu->len = len;
+        int_to_scsilun(sdev->lun, &iu->lun);
+        memcpy(iu->cdb, cmnd->cmnd, cmnd->cmd_len);
+
+        usb_fill_bulk_urb(urb, udev, devinfo->cmd_pipe, iu, sizeof(*iu) + len,
+                                                        usb_free_urb, NULL);
+        urb->transfer_flags |= URB_FREE_BUFFER;
+ out:
+        return urb;
+ free:
+        usb_free_urb(urb);
+        return NULL;
+}
+
+/*
+ * Why should I request the Status IU before sending the Command IU?  Spec
+ * says to, but also says the device may receive them in any order.  Seems
+ * daft to me.
+ */
+
+static int uas_submit_urbs(struct scsi_cmnd *cmnd,
+                                        struct uas_dev_info *devinfo, gfp_t gfp)
+{
+        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
+
+        if (cmdinfo->state & ALLOC_SENSE_URB) {
+                cmdinfo->sense_urb = uas_alloc_sense_urb(devinfo, gfp, cmnd,
+                                                        cmdinfo->stream);
+                if (!cmdinfo->sense_urb)
+                        return SCSI_MLQUEUE_DEVICE_BUSY;
+                cmdinfo->state &= ~ALLOC_SENSE_URB;
+        }
+
+        if (cmdinfo->state & SUBMIT_SENSE_URB) {
+                if (usb_submit_urb(cmdinfo->sense_urb, gfp)) {
+                        scmd_printk(KERN_INFO, cmnd,
+                                        "sense urb submission failure\n");
+                        return SCSI_MLQUEUE_DEVICE_BUSY;
+                }
+                cmdinfo->state &= ~SUBMIT_SENSE_URB;
+        }
+
+        if (cmdinfo->state & ALLOC_DATA_IN_URB) {
+                cmdinfo->data_in_urb = uas_alloc_data_urb(devinfo, gfp,
+                                        devinfo->data_in_pipe, cmdinfo->stream,
+                                        scsi_in(cmnd), DMA_FROM_DEVICE);
+                if (!cmdinfo->data_in_urb)
+                        return SCSI_MLQUEUE_DEVICE_BUSY;
+                cmdinfo->state &= ~ALLOC_DATA_IN_URB;
+        }
+
+        if (cmdinfo->state & SUBMIT_DATA_IN_URB) {
+                if (usb_submit_urb(cmdinfo->data_in_urb, gfp)) {
+                        scmd_printk(KERN_INFO, cmnd,
+                                        "data in urb submission failure\n");
+                        return SCSI_MLQUEUE_DEVICE_BUSY;
+                }
+                cmdinfo->state &= ~SUBMIT_DATA_IN_URB;
+        }
+
+        if (cmdinfo->state & ALLOC_DATA_OUT_URB) {
+                cmdinfo->data_out_urb = uas_alloc_data_urb(devinfo, gfp,
+                                        devinfo->data_out_pipe, cmdinfo->stream,
+                                        scsi_out(cmnd), DMA_TO_DEVICE);
+                if (!cmdinfo->data_out_urb)
+                        return SCSI_MLQUEUE_DEVICE_BUSY;
+                cmdinfo->state &= ~ALLOC_DATA_OUT_URB;
+        }
+
+        if (cmdinfo->state & SUBMIT_DATA_OUT_URB) {
+                if (usb_submit_urb(cmdinfo->data_out_urb, gfp)) {
+                        scmd_printk(KERN_INFO, cmnd,
+                                        "data out urb submission failure\n");
+                        return SCSI_MLQUEUE_DEVICE_BUSY;
+                }
+                cmdinfo->state &= ~SUBMIT_DATA_OUT_URB;
+        }
+
+        if (cmdinfo->state & ALLOC_CMD_URB) {
+                cmdinfo->cmd_urb = uas_alloc_cmd_urb(devinfo, gfp, cmnd,
+                                                        cmdinfo->stream);
+                if (!cmdinfo->cmd_urb)
+                        return SCSI_MLQUEUE_DEVICE_BUSY;
+                cmdinfo->state &= ~ALLOC_CMD_URB;
+        }
+
+        if (cmdinfo->state & SUBMIT_CMD_URB) {
+                if (usb_submit_urb(cmdinfo->cmd_urb, gfp)) {
+                        scmd_printk(KERN_INFO, cmnd,
+                                        "cmd urb submission failure\n");
+                        return SCSI_MLQUEUE_DEVICE_BUSY;
+                }
+                cmdinfo->state &= ~SUBMIT_CMD_URB;
+        }
+
+        return 0;
+}
+
+static int uas_queuecommand(struct scsi_cmnd *cmnd,
+                                        void (*done)(struct scsi_cmnd *))
+{
+        struct scsi_device *sdev = cmnd->device;
+        struct uas_dev_info *devinfo = sdev->hostdata;
+        struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
+        int err;
+
+        BUILD_BUG_ON(sizeof(struct uas_cmd_info) > sizeof(struct scsi_pointer));
+
+        if (!cmdinfo->sense_urb && sdev->current_cmnd)
+                return SCSI_MLQUEUE_DEVICE_BUSY;
+
+        if (blk_rq_tagged(cmnd->request)) {
+                cmdinfo->stream = cmnd->request->tag + 1;
+        } else {
+                sdev->current_cmnd = cmnd;
+                cmdinfo->stream = 1;
+        }
+
+        cmnd->scsi_done = done;
+
+        cmdinfo->state = ALLOC_SENSE_URB | SUBMIT_SENSE_URB |
+                        ALLOC_CMD_URB | SUBMIT_CMD_URB;
+
+        switch (cmnd->sc_data_direction) {
+        case DMA_FROM_DEVICE:
+                cmdinfo->state |= ALLOC_DATA_IN_URB | SUBMIT_DATA_IN_URB;
+                break;
+        case DMA_BIDIRECTIONAL:
+                cmdinfo->state |= ALLOC_DATA_IN_URB | SUBMIT_DATA_IN_URB;
+        case DMA_TO_DEVICE:
+                cmdinfo->state |= ALLOC_DATA_OUT_URB | SUBMIT_DATA_OUT_URB;
+        case DMA_NONE:
+                break;
+        }
+
+        if (!devinfo->use_streams) {
+                cmdinfo->state &= ~(SUBMIT_DATA_IN_URB | SUBMIT_DATA_OUT_URB);
+                cmdinfo->stream = 0;
+        }
+
+        err = uas_submit_urbs(cmnd, devinfo, GFP_ATOMIC);
+        if (err) {
+                /* If we did nothing, give up now */
+                if (cmdinfo->state & SUBMIT_SENSE_URB) {
+                        usb_free_urb(cmdinfo->sense_urb);
+                        return SCSI_MLQUEUE_DEVICE_BUSY;
+                }
+                spin_lock(&uas_work_lock);
+                list_add_tail(&cmdinfo->list, &uas_work_list);
+                spin_unlock(&uas_work_lock);
+                schedule_work(&uas_work);
+        }
+
+        return 0;
+}
+
+static int uas_eh_abort_handler(struct scsi_cmnd *cmnd)
+{
+        struct scsi_device *sdev = cmnd->device;
+        sdev_printk(KERN_INFO, sdev, "%s tag %d\n", __func__,
+                                                        cmnd->request->tag);
+
+/* XXX: Send ABORT TASK Task Management command */
+        return FAILED;
+}
+
+static int uas_eh_device_reset_handler(struct scsi_cmnd *cmnd)
+{
+        struct scsi_device *sdev = cmnd->device;
+        sdev_printk(KERN_INFO, sdev, "%s tag %d\n", __func__,
+                                                        cmnd->request->tag);
+
+/* XXX: Send LOGICAL UNIT RESET Task Management command */
+        return FAILED;
+}
+
+static int uas_eh_target_reset_handler(struct scsi_cmnd *cmnd)
+{
+        struct scsi_device *sdev = cmnd->device;
+        sdev_printk(KERN_INFO, sdev, "%s tag %d\n", __func__,
+                                                        cmnd->request->tag);
+
+/* XXX: Can we reset just the one USB interface?
+ * Would calling usb_set_interface() have the right effect?
+ */
+        return FAILED;
+}
+
+static int uas_eh_bus_reset_handler(struct scsi_cmnd *cmnd)
+{
+        struct scsi_device *sdev = cmnd->device;
+        struct uas_dev_info *devinfo = sdev->hostdata;
+        struct usb_device *udev = devinfo->udev;
+
+        sdev_printk(KERN_INFO, sdev, "%s tag %d\n", __func__,
+                                                        cmnd->request->tag);
+
+        if (usb_reset_device(udev))
+                return SUCCESS;
+
+        return FAILED;
+}
+
+static int uas_slave_alloc(struct scsi_device *sdev)
+{
+        sdev->hostdata = (void *)sdev->host->hostdata[0];
+        return 0;
+}
+
+static int uas_slave_configure(struct scsi_device *sdev)
+{
+        struct uas_dev_info *devinfo = sdev->hostdata;
+        scsi_set_tag_type(sdev, MSG_ORDERED_TAG);
+        scsi_activate_tcq(sdev, devinfo->qdepth - 1);
+        return 0;
+}
+
+static struct scsi_host_template uas_host_template = {
+        .module = THIS_MODULE,
+        .name = "uas",
+        .queuecommand = uas_queuecommand,
+        .slave_alloc = uas_slave_alloc,
+        .slave_configure = uas_slave_configure,
+        .eh_abort_handler = uas_eh_abort_handler,
+        .eh_device_reset_handler = uas_eh_device_reset_handler,
+        .eh_target_reset_handler = uas_eh_target_reset_handler,
+        .eh_bus_reset_handler = uas_eh_bus_reset_handler,
+        .can_queue = 65536,     /* Is there a limit on the _host_ ? */
+        .this_id = -1,
+        .sg_tablesize = SG_NONE,
+        .cmd_per_lun = 1,       /* until we override it */
+        .skip_settle_delay = 1,
+        .ordered_tag = 1,
+};
+
+static struct usb_device_id uas_usb_ids[] = {
+        { USB_INTERFACE_INFO(USB_CLASS_MASS_STORAGE, USB_SC_SCSI, USB_PR_BULK) },
+        { USB_INTERFACE_INFO(USB_CLASS_MASS_STORAGE, USB_SC_SCSI, USB_PR_UAS) },
+        /* 0xaa is a prototype device I happen to have access to */
+        { USB_INTERFACE_INFO(USB_CLASS_MASS_STORAGE, USB_SC_SCSI, 0xaa) },
+        { }
+};
+MODULE_DEVICE_TABLE(usb, uas_usb_ids);
+
+static void uas_configure_endpoints(struct uas_dev_info *devinfo)
+{
+        struct usb_host_endpoint *eps[4] = { };
+        struct usb_interface *intf = devinfo->intf;
+        struct usb_device *udev = devinfo->udev;
+        struct usb_host_endpoint *endpoint = intf->cur_altsetting->endpoint;
+        unsigned i, n_endpoints = intf->cur_altsetting->desc.bNumEndpoints;
+
+        devinfo->uas_sense_old = 0;
+
+        for (i = 0; i < n_endpoints; i++) {
+                unsigned char *extra = endpoint[i].extra;
+                int len = endpoint[i].extralen;
+                while (len > 1) {
+                        if (extra[1] == USB_DT_PIPE_USAGE) {
+                                unsigned pipe_id = extra[2];
+                                if (pipe_id > 0 && pipe_id < 5)
+                                        eps[pipe_id - 1] = &endpoint[i];
+                                break;
+                        }
+                        len -= extra[0];
+                        extra += extra[0];
+                }
+        }
+
+        /*
+         * Assume that if we didn't find a control pipe descriptor, we're
+         * using a device with old firmware that happens to be set up like
+         * this.
+         */
+        if (!eps[0]) {
+                devinfo->cmd_pipe = usb_sndbulkpipe(udev, 1);
+                devinfo->status_pipe = usb_rcvbulkpipe(udev, 1);
+                devinfo->data_in_pipe = usb_rcvbulkpipe(udev, 2);
+                devinfo->data_out_pipe = usb_sndbulkpipe(udev, 2);
+
+                eps[1] = usb_pipe_endpoint(udev, devinfo->status_pipe);
+                eps[2] = usb_pipe_endpoint(udev, devinfo->data_in_pipe);
+                eps[3] = usb_pipe_endpoint(udev, devinfo->data_out_pipe);
+        } else {
+                devinfo->cmd_pipe = usb_sndbulkpipe(udev,
+                                                eps[0]->desc.bEndpointAddress);
+                devinfo->status_pipe = usb_rcvbulkpipe(udev,
+                                                eps[1]->desc.bEndpointAddress);
+                devinfo->data_in_pipe = usb_rcvbulkpipe(udev,
+                                                eps[2]->desc.bEndpointAddress);
+                devinfo->data_out_pipe = usb_sndbulkpipe(udev,
+                                                eps[3]->desc.bEndpointAddress);
+        }
+
+        devinfo->qdepth = usb_alloc_streams(devinfo->intf, eps + 1, 3, 256,
+                                                                GFP_KERNEL);
+        if (devinfo->qdepth < 0) {
+                devinfo->qdepth = 256;
+                devinfo->use_streams = 0;
+        } else {
+                devinfo->use_streams = 1;
+        }
+}
+
+/*
+ * XXX: What I'd like to do here is register a SCSI host for each USB host in
+ * the system.  Follow usb-storage's design of registering a SCSI host for
+ * each USB device for the moment.  Can implement this by walking up the
+ * USB hierarchy until we find a USB host.
+ */
+static int uas_probe(struct usb_interface *intf, const struct usb_device_id *id)
+{
+        int result;
+        struct Scsi_Host *shost;
+        struct uas_dev_info *devinfo;
+        struct usb_device *udev = interface_to_usbdev(intf);
+
+        if (id->bInterfaceProtocol == 0x50) {
+                int ifnum = intf->cur_altsetting->desc.bInterfaceNumber;
+/* XXX: Shouldn't assume that 1 is the alternative we want */
+                int ret = usb_set_interface(udev, ifnum, 1);
+                if (ret)
+                        return -ENODEV;
+        }
+
+        devinfo = kmalloc(sizeof(struct uas_dev_info), GFP_KERNEL);
+        if (!devinfo)
+                return -ENOMEM;
+
+        result = -ENOMEM;
+        shost = scsi_host_alloc(&uas_host_template, sizeof(void *));
+        if (!shost)
+                goto free;
+
+        shost->max_cmd_len = 16 + 252;
+        shost->max_id = 1;
+        shost->sg_tablesize = udev->bus->sg_tablesize;
+
+        result = scsi_add_host(shost, &intf->dev);
+        if (result)
+                goto free;
+        shost->hostdata[0] = (unsigned long)devinfo;
+
+        devinfo->intf = intf;
+        devinfo->udev = udev;
+        uas_configure_endpoints(devinfo);
+
+        scsi_scan_host(shost);
+        usb_set_intfdata(intf, shost);
+        return result;
+ free:
+        kfree(devinfo);
+        if (shost)
+                scsi_host_put(shost);
+        return result;
+}
+
+static int uas_pre_reset(struct usb_interface *intf)
+{
+/* XXX: Need to return 1 if it's not our device in error handling */
+        return 0;
+}
+
+static int uas_post_reset(struct usb_interface *intf)
+{
+/* XXX: Need to return 1 if it's not our device in error handling */
+        return 0;
+}
+
+static void uas_disconnect(struct usb_interface *intf)
+{
+        struct usb_device *udev = interface_to_usbdev(intf);
+        struct usb_host_endpoint *eps[3];
+        struct Scsi_Host *shost = usb_get_intfdata(intf);
+        struct uas_dev_info *devinfo = (void *)shost->hostdata[0];
+
+        scsi_remove_host(shost);
+
+        eps[0] = usb_pipe_endpoint(udev, devinfo->status_pipe);
+        eps[1] = usb_pipe_endpoint(udev, devinfo->data_in_pipe);
+        eps[2] = usb_pipe_endpoint(udev, devinfo->data_out_pipe);
+        usb_free_streams(intf, eps, 3, GFP_KERNEL);
+
+        kfree(devinfo);
+}
+
+/*
+ * XXX: Should this plug into libusual so we can auto-upgrade devices from
+ * Bulk-Only to UAS?
+ */
+static struct usb_driver uas_driver = {
+        .name = "uas",
+        .probe = uas_probe,
+        .disconnect = uas_disconnect,
+        .pre_reset = uas_pre_reset,
+        .post_reset = uas_post_reset,
+        .id_table = uas_usb_ids,
+};
+
+static int uas_init(void)
+{
+        return usb_register(&uas_driver);
+}
+
+static void uas_exit(void)
+{
+        usb_deregister(&uas_driver);
+}
+
+module_init(uas_init);
+module_exit(uas_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Matthew Wilcox and Sarah Sharp");