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>

2 files changed, 43 insertions, 1 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],