[PATCH] USB: Patch to signal underflow in usb-storage driver

This patch causes the usb-storage driver to return an error indication
(DID_ERROR together with SUGGEST_RETRY) when the amount transferred by a
SCSI command is smaller than the "underflow" amount.  Some devices, like
the iRiver H100 series, occasionally transfer 0 bytes with GOOD status.
This change will make the sd driver aware that something unexpected has
happened so it can retry the command.
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 <greg@kroah.com>

drivers/usb/storage/transport.c

@@ -708,6 +708,12 @@ void usb_stor_invoke_transport(Scsi_Cmnd *srb, struct us_data *us)
 			srb->sense_buffer[0] = 0x0;
 		}
 	}
+
+	/* Did we transfer less than the minimum amount required? */
+	if (srb->result == SAM_STAT_GOOD &&
+			srb->request_bufflen - srb->resid < srb->underflow)
+		srb->result = (DID_ERROR << 16) | (SUGGEST_RETRY << 24);
+
 	return;
 
 	/* abort processing: the bulk-only transport requires a reset