scsiglue.c

底层驱动开发

/* Driver for USB Mass Storage compliant devices
 * SCSI layer glue code
 *
 * $Id: scsiglue.c,v 1.26 2002/04/22 03:39:43 mdharm Exp $
 *
 * Current development and maintenance by:
 *   (c) 1999-2002 Matthew Dharm ([e-mail])
 *
 * Developed with the assistance of:
 *   (c) 2000 David L. Brown, Jr. ([e-mail])
 *   (c) 2000 Stephen J. Gowdy ([e-mail])
 *
 * Initial work by:
 *   (c) 1999 Michael Gee ([e-mail])
 *
 * This driver is based on the 'USB Mass Storage Class' document. This
 * describes in detail the protocol used to communicate with such
 * devices.  Clearly, the designers had SCSI and ATAPI commands in
 * mind when they created this document.  The commands are all very
 * similar to commands in the SCSI-II and ATAPI specifications.
 *
 * It is important to note that in a number of cases this class
 * exhibits class-specific exemptions from the USB specification.
 * Notably the usage of NAK, STALL and ACK differs from the norm, in
 * that they are used to communicate wait, failed and OK on commands.
 *
 * Also, for certain devices, the interrupt endpoint is used to convey
 * status of a command.
 *
 * Please see http://www.one-eyed-alien.net/~mdharm/linux-usb for more
 * information about this driver.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/slab.h>
#include <linux/module.h>

#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_devinfo.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_eh.h>

#include "usb.h"
#include "scsiglue.h"
#include "debug.h"
#include "transport.h"
#include "protocol.h"

/***********************************************************************
 * Host functions 
 ***********************************************************************/

static const char* host_info(struct Scsi_Host *host)
{
	return "SCSI emulation for USB Mass Storage devices";
}

static int slave_alloc (struct scsi_device *sdev)
{
	/*
	 * Set the INQUIRY transfer length to 36.  We don't use any of
	 * the extra data and many devices choke if asked for more or
	 * less than 36 bytes.
	 */
	sdev->inquiry_len = 36;
	return 0;
}

static int slave_configure(struct scsi_device *sdev)
{
	struct us_data *us = host_to_us(sdev->host);

	/* Scatter-gather buffers (all but the last) must have a length
	 * divisible by the bulk maxpacket size.  Otherwise a data packet
	 * would end up being short, causing a premature end to the data
	 * transfer.  Since high-speed bulk pipes have a maxpacket size
	 * of 512, we'll use that as the scsi device queue's DMA alignment
	 * mask.  Guaranteeing proper alignment of the first buffer will
	 * have the desired effect because, except at the beginning and
	 * the end, scatter-gather buffers follow page boundaries. */
	blk_queue_dma_alignment(sdev->request_queue, (512 - 1));

	/* Set the SCSI level to at least 2.  We'll leave it at 3 if that's
	 * what is originally reported.  We need this to avoid confusing
	 * the SCSI layer with devices that report 0 or 1, but need 10-byte
	 * commands (ala ATAPI devices behind certain bridges, or devices
	 * which simply have broken INQUIRY data).
	 *
	 * NOTE: This means /dev/sg programs (ala cdrecord) will get the
	 * actual information.  This seems to be the preference for
	 * programs like that.
	 *
	 * NOTE: This also means that /proc/scsi/scsi and sysfs may report
	 * the actual value or the modified one, depending on where the
	 * data comes from.
	 */
	if (sdev->scsi_level < SCSI_2)
		sdev->scsi_level = SCSI_2;

	/* According to the technical support people at Genesys Logic,
	 * devices using their chips have problems transferring more than
	 * 32 KB at a time.  In practice people have found that 64 KB
	 * works okay and that's what Windows does.  But we'll be
	 * conservative; people can always use the sysfs interface to
	 * increase max_sectors. */
	if (le16_to_cpu(us->pusb_dev->descriptor.idVendor) == USB_VENDOR_ID_GENESYS &&
			sdev->request_queue->max_sectors > 64)
		blk_queue_max_sectors(sdev->request_queue, 64);

	/* We can't put these settings in slave_alloc() because that gets
	 * called before the device type is known.  Consequently these
	 * settings can't be overridden via the scsi devinfo mechanism. */
	if (sdev->type == TYPE_DISK) {

		/* Disk-type devices use MODE SENSE(6) if the protocol
		 * (SubClass) is Transparent SCSI, otherwise they use
		 * MODE SENSE(10). */
		if (us->subclass != US_SC_SCSI)
			sdev->use_10_for_ms = 1;

		/* Many disks only accept MODE SENSE transfer lengths of
		 * 192 bytes (that's what Windows uses). */
		sdev->use_192_bytes_for_3f = 1;

		/* Some devices don't like MODE SENSE with page=0x3f,
		 * which is the command used for checking if a device
		 * is write-protected.  Now that we tell the sd driver
		 * to do a 192-byte transfer with this command the
		 * majority of devices work fine, but a few still can't
		 * handle it.  The sd driver will simply assume those
		 * devices are write-enabled. */
		if (us->flags & US_FL_NO_WP_DETECT)
			sdev->skip_ms_page_3f = 1;

		/* A number of devices have problems with MODE SENSE for
		 * page x08, so we will skip it. */
		sdev->skip_ms_page_8 = 1;

		/* Some disks return the total number of blocks in response
		 * to READ CAPACITY rather than the highest block number.
		 * If this device makes that mistake, tell the sd driver. */
		if (us->flags & US_FL_FIX_CAPACITY)
			sdev->fix_capacity = 1;

		/* Some devices report a SCSI revision level above 2 but are
		 * unable to handle the REPORT LUNS command (for which
		 * support is mandatory at level 3).  Since we already have
		 * a Get-Max-LUN request, we won't lose much by setting the
		 * revision level down to 2.  The only devices that would be
		 * affected are those with sparse LUNs. */
		sdev->scsi_level = SCSI_2;

		/* USB-IDE bridges tend to report SK = 0x04 (Non-recoverable
		 * Hardware Error) when any low-level error occurs,
		 * recoverable or not.  Setting this flag tells the SCSI
		 * midlayer to retry such commands, which frequently will
		 * succeed and fix the error.  The worst this can lead to
		 * is an occasional series of retries that will all fail. */
		sdev->retry_hwerror = 1;

	} else {

		/* Non-disk-type devices don't need to blacklist any pages
		 * or to force 192-byte transfer lengths for MODE SENSE.
		 * But they do need to use MODE SENSE(10). */
		sdev->use_10_for_ms = 1;
	}

	/* Some devices choke when they receive a PREVENT-ALLOW MEDIUM
	 * REMOVAL command, so suppress those commands. */
	if (us->flags & US_FL_NOT_LOCKABLE)
		sdev->lockable = 0;

	/* this is to satisfy the compiler, tho I don't think the 
	 * return code is ever checked anywhere. */
	return 0;
}

/* queue a command */
/* This is always called with scsi_lock(host) held */
static int queuecommand(struct scsi_cmnd *srb,
			void (*done)(struct scsi_cmnd *))
{
	struct us_data *us = host_to_us(srb->device->host);

	US_DEBUGP("%s called\n", __FUNCTION__);

	/* check for state-transition errors */
	if (us->srb != NULL) {
		printk(KERN_ERR USB_STORAGE "Error in %s: us->srb = %p\n",
			__FUNCTION__, us->srb);
		return SCSI_MLQUEUE_HOST_BUSY;
	}

	/* fail the command if we are disconnecting */
	if (test_bit(US_FLIDX_DISCONNECTING, &us->flags)) {
		US_DEBUGP("Fail command during disconnect\n");
		srb->result = DID_NO_CONNECT << 16;
		done(srb);
		return 0;
	}

	/* enqueue the command and wake up the control thread */
	srb->scsi_done = done;
	us->srb = srb;
	up(&(us->sema));

	return 0;
}

/***********************************************************************
 * Error handling functions
 ***********************************************************************/

/* Command timeout and abort */
static int command_abort(struct scsi_cmnd *srb)
{
	struct us_data *us = host_to_us(srb->device->host);

	US_DEBUGP("%s called\n", __FUNCTION__);

	/* us->srb together with the TIMED_OUT, RESETTING, and ABORTING
	 * bits are protected by the host lock. */
	scsi_lock(us_to_host(us));

	/* Is this command still active? */
	if (us->srb != srb) {
		scsi_unlock(us_to_host(us));
		US_DEBUGP ("-- nothing to abort\n");
		return FAILED;