[PATCH] USB Storage: revert GetMaxLUN strictness

This is patch as384.  It reverts some of our sanity checks on the GetMaxLUN
part of the Bulk-only protocol.  Apparently, this is one area where vendors
can't even get close to correct.  So, in the face of any sort of error, we
assume a single LUN.

We also include some comments so we don't make this mistake again.
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

@@ -911,7 +911,6 @@ int usb_stor_Bulk_max_lun(struct us_data *us)
 	int result;
 
 	/* issue the command */
-	us->iobuf[0] = 0;
 	result = usb_stor_control_msg(us, us->recv_ctrl_pipe,
 				 US_BULK_GET_MAX_LUN, 
 				 USB_DIR_IN | USB_TYPE_CLASS | 
@@ -922,7 +921,7 @@ int usb_stor_Bulk_max_lun(struct us_data *us)
 		  result, us->iobuf[0]);
 
 	/* if we have a successful request, return the result */
-	if (result >= 0)
+	if (result > 0)
 		return us->iobuf[0];
 
 	/* 
@@ -934,13 +933,16 @@ int usb_stor_Bulk_max_lun(struct us_data *us)
 	if (result == -EPIPE) {
 		usb_stor_clear_halt(us, us->recv_bulk_pipe);
 		usb_stor_clear_halt(us, us->send_bulk_pipe);
-		/* return the default -- no LUNs */
-		return 0;
 	}
 
-	/* An answer or a STALL are the only valid responses.  If we get
-	 * something else, return an indication of error */
-	return -1;
+	/*
+	 * Some devices don't like GetMaxLUN.  They may STALL the control
+	 * pipe, they may return a zero-length result, they may do nothing at
+	 * all and timeout, or they may fail in even more bizarrely creative
+	 * ways.  In these cases the best approach is to use the default
+	 * value: only one LUN.
+	 */
+	return 0;
 }
 
 int usb_stor_Bulk_transport(struct scsi_cmnd *srb, struct us_data *us)