usb-storage: SCSI level fixes

This patch (as835) removes from usb-storage the code which sets all
devices to a SCSI level of at least SCSI-2.  The original reasons for
doing this no longer apply, and in fact it prevents certain kinds of
ATA pass-thru commands from being used.

The patch also marks CB and CBI devices that are SCSI-0 (legacy SCSI)
as being single-LUN, since the combined SCSI-over-USB transport
protocol has no way to convey LUN information to these devices.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 13 insertions, 18 deletions

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index e1072d52d641..70234f5dbeeb 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -110,23 +110,6 @@ static int slave_configure(struct scsi_device *sdev)
          * 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 = sdev->sdev_target->scsi_level = SCSI_2;
-
         /* Many devices have trouble transfering more than 32KB at a time,
          * while others have trouble with more than 64K. At this time we
          * are limiting both to 32K (64 sectores).
@@ -176,7 +159,9 @@ static int slave_configure(struct scsi_device *sdev)
                  * 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 = sdev->sdev_target->scsi_level = SCSI_2;
+                if (sdev->scsi_level > SCSI_2)
+                        sdev->sdev_target->scsi_level =
+                                        sdev->scsi_level = SCSI_2;
 
                 /* USB-IDE bridges tend to report SK = 0x04 (Non-recoverable
                  * Hardware Error) when any low-level error occurs,
@@ -194,6 +179,16 @@ static int slave_configure(struct scsi_device *sdev)
                 sdev->use_10_for_ms = 1;
         }
 
+        /* The CB and CBI transports have no way to pass LUN values
+         * other than the bits in the second byte of a CDB.  But those
+         * bits don't get set to the LUN value if the device reports
+         * scsi_level == 0 (UNKNOWN).  Hence such devices must necessarily
+         * be single-LUN.
+         */
+        if ((us->protocol == US_PR_CB || us->protocol == US_PR_CBI) &&
+                        sdev->scsi_level == SCSI_UNKNOWN)
+                us->max_lun = 0;
+
         /* Some devices choke when they receive a PREVENT-ALLOW MEDIUM
          * REMOVAL command, so suppress those commands. */
         if (us->flags & US_FL_NOT_LOCKABLE)