USB: storage devices and SAT

Add the SANE SENSE flag to indicate that a device is capable of handling
more than 18-bytes of sense data.  This functionality is required for
USB-ATA bridges implementing SAT.  A future patch will actually enable this
function for several devices.

The logic behind this is that we can detect support for SANE_SENSE in a few ways:
 1) ATA PASS THROUGH (12) or (16) execute successfully
 2) SPC-3 or higher is in use
 3) A previous CHECK CONDITION occurred with sense format 70-73 and had
    a length greater than 18-bytes total

Signed-off-by: Ben Efros <ben@pc-doctor.com>
Signed-off-by: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 46 insertions, 3 deletions

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 09779f6a8179..1b35e011a34f 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -170,6 +170,10 @@ static int slave_configure(struct scsi_device *sdev)
                 if (us->fflags & US_FL_CAPACITY_HEURISTICS)
                         sdev->guess_capacity = 1;
 
+                /* assume SPC3 or latter devices support sense size > 18 */
+                if (sdev->scsi_level > SCSI_SPC_2)
+                        us->fflags |= US_FL_SANE_SENSE;
+
                 /* 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
diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c
index 2058db41618c..f584e72cc689 100644
--- a/drivers/usb/storage/transport.c
+++ b/drivers/usb/storage/transport.c
@@ -579,6 +579,20 @@ void usb_stor_invoke_transport(struct scsi_cmnd *srb, struct us_data *us)
         }
 
         /*
+         * Determine if this device is SAT by seeing if the
+         * command executed successfully.  Otherwise we'll have
+         * to wait for at least one CHECK_CONDITION to determine
+         * SANE_SENSE support
+         */
+        if ((srb->cmnd[0] == ATA_16 || srb->cmnd[0] == ATA_12) &&
+            result == USB_STOR_TRANSPORT_GOOD &&
+            !(us->fflags & US_FL_SANE_SENSE) &&
+            !(srb->cmnd[2] & 0x20)) {
+                US_DEBUGP("-- SAT supported, increasing auto-sense\n");
+                us->fflags |= US_FL_SANE_SENSE;
+        }
+
+        /*
          * A short transfer on a command where we don't expect it
          * is unusual, but it doesn't mean we need to auto-sense.
          */
@@ -595,10 +609,15 @@ void usb_stor_invoke_transport(struct scsi_cmnd *srb, struct us_data *us)
         if (need_auto_sense) {
                 int temp_result;
                 struct scsi_eh_save ses;
+                int sense_size = US_SENSE_SIZE;
+
+                /* device supports and needs bigger sense buffer */
+                if (us->fflags & US_FL_SANE_SENSE)
+                        sense_size = ~0;
 
                 US_DEBUGP("Issuing auto-REQUEST_SENSE\n");
 
-                scsi_eh_prep_cmnd(srb, &ses, NULL, 0, US_SENSE_SIZE);
+                scsi_eh_prep_cmnd(srb, &ses, NULL, 0, sense_size);
 
                 /* FIXME: we must do the protocol translation here */
                 if (us->subclass == US_SC_RBC || us->subclass == US_SC_SCSI ||
@@ -632,6 +651,25 @@ void usb_stor_invoke_transport(struct scsi_cmnd *srb, struct us_data *us)
                         return;
                 }
 
+                /* If the sense data returned is larger than 18-bytes then we
+                 * assume this device supports requesting more in the future.
+                 * The response code must be 70h through 73h inclusive.
+                 */
+                if (srb->sense_buffer[7] > (US_SENSE_SIZE - 8) &&
+                    !(us->fflags & US_FL_SANE_SENSE) &&
+                    (srb->sense_buffer[0] & 0x7C) == 0x70) {
+                        US_DEBUGP("-- SANE_SENSE support enabled\n");
+                        us->fflags |= US_FL_SANE_SENSE;
+
+                        /* Indicate to the user that we truncated their sense
+                         * because we didn't know it supported larger sense.
+                         */
+                        US_DEBUGP("-- Sense data truncated to %i from %i\n",
+                                  US_SENSE_SIZE,
+                                  srb->sense_buffer[7] + 8);
+                        srb->sense_buffer[7] = (US_SENSE_SIZE - 8);
+                }
+
                 US_DEBUGP("-- Result from auto-sense is %d\n", temp_result);
                 US_DEBUGP("-- code: 0x%x, key: 0x%x, ASC: 0x%x, ASCQ: 0x%x\n",
                           srb->sense_buffer[0],
diff --git a/include/linux/usb_usual.h b/include/linux/usb_usual.h
index d9a3bbe38e6b..998e5cbbf29e 100644
--- a/include/linux/usb_usual.h
+++ b/include/linux/usb_usual.h
@@ -52,8 +52,9 @@
         US_FLAG(MAX_SECTORS_MIN,0x00002000)                     \
                 /* Sets max_sectors to arch min */              \
         US_FLAG(BULK_IGNORE_TAG,0x00004000)                     \
-                /* Ignore tag mismatch in bulk operations */
-
+                /* Ignore tag mismatch in bulk operations */    \
+        US_FLAG(SANE_SENSE,     0x00008000)
+                /* Sane Sense (> 18 bytes) */
 
 #define US_FLAG(name, value)    US_FL_##name = value ,
 enum { US_DO_ALL_FLAGS };