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 f2a2b8e647c..8dac57f53d8 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 8a372bac0e4..f2767cf2e22 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 ef7e5a8ceab..0332aa5df24 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 00000000000..2054b1e25a6
--- /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");