[PATCH] sbp2: default to serialize_io=1

Set serialize_io=1 by default.  This is safer and required by seemingly more
and more hardware.  It causes little or no performance loss for S400 devices.
Performance of S800 1394b devices may drop by 25...30%.  Therefore make the
parameter's description and dmesg message clearer about performance impact.

Update description of the max_speed parameter too.  IEEE1394_SPEED_MAX is
currently S800.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NJody McIntyre <scjody@steamballoon.com>
Cc: Ben Collins <bcollins@debian.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

drivers/ieee1394/sbp2.c

@@ -97,16 +97,18 @@ static char version[] __devinitdata =
  */
 static int max_speed = IEEE1394_SPEED_MAX;
 module_param(max_speed, int, 0644);
-MODULE_PARM_DESC(max_speed, "Force max speed (3 = 800mb, 2 = 400mb default, 1 = 200mb, 0 = 100mb)");
+MODULE_PARM_DESC(max_speed, "Force max speed (3 = 800mb, 2 = 400mb, 1 = 200mb, 0 = 100mb)");
 
 /*
  * Set serialize_io to 1 if you'd like only one scsi command sent
  * down to us at a time (debugging). This might be necessary for very
  * badly behaved sbp2 devices.
+ *
+ * TODO: Make this configurable per device.
  */
-static int serialize_io;
+static int serialize_io = 1;
 module_param(serialize_io, int, 0444);
-MODULE_PARM_DESC(serialize_io, "Serialize all I/O coming down from the scsi drivers (default = 0)");
+MODULE_PARM_DESC(serialize_io, "Serialize I/O coming from scsi drivers (default = 1, faster = 0)");
 
 /*
  * Bump up max_sectors if you'd like to support very large sized
@@ -2857,7 +2859,8 @@ static int sbp2_module_init(void)
 
 	/* Module load debug option to force one command at a time (serializing I/O) */
 	if (serialize_io) {
-		SBP2_ERR("Driver forced to serialize I/O (serialize_io = 1)");
+		SBP2_INFO("Driver forced to serialize I/O (serialize_io=1)");
+		SBP2_INFO("Try serialize_io=0 for better performance");
 		scsi_driver_template.can_queue = 1;
 		scsi_driver_template.cmd_per_lun = 1;
 	}