[PATCH] PATCH: usb-storage: move GetMaxLUN later in time

This patch is originally from Alan Stern (as557).  It has been re-diffed
against a current tree, and I also corrected a minor merging error.

Some time ago we introduced a delay before device scanning, because many
devices do not like to receive SCSI commands right after enumeration.
Now it turns out there's a device that doesn't like to receive
Get-Max-LUN right after enumeration either.  Accordingly this patch
delays the Get-Max-LUN request until the beginning of the scanning
procedure.  This fixes Bugzilla entry #5010.

Three things are worth noting.  First, I removed the locking code from
usb_stor_acquire_resources.  It's not needed, because the locking is to
protect against disconnect events and acquire_resources is only called
during probe (so the disconnect routine can't be called).  Second, I
initialized to 0 the buffer used for the Get-Max-LUN response.  It's not
really necessary, but it will prevent random values from showing up in
the debugging log when the request fails.  Third, I added a test against
the SINGLE_LUN flag.  This will allow us to use the flag to indicate
Bulk-only devices that can't handle Get-Max-LUN.
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 <gregkh@suse.de>

drivers/usb/storage/transport.c

@@ -923,6 +923,7 @@ 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 | 

drivers/usb/storage/usb.c

@@ -747,25 +747,13 @@ static int usb_stor_acquire_resources(struct us_data *us)
 		return -ENOMEM;
 	}
 
-	/* Lock the device while we carry out the next two operations */
-	down(&us->dev_semaphore);
-
-	/* For bulk-only devices, determine the max LUN value */
-	if (us->protocol == US_PR_BULK) {
-		p = usb_stor_Bulk_max_lun(us);
-		if (p < 0) {
-			up(&us->dev_semaphore);
-			return p;
-		}
-		us->max_lun = p;
-	}
-
 	/* Just before we start our control thread, initialize
 	 * the device if it needs initialization */
-	if (us->unusual_dev->initFunction)
-		us->unusual_dev->initFunction(us);
-
-	up(&us->dev_semaphore);
+	if (us->unusual_dev->initFunction) {
+		p = us->unusual_dev->initFunction(us);
+		if (p)
+			return p;
+	}
 
 	/* Start up our control thread */
 	p = kernel_thread(usb_stor_control_thread, us, CLONE_VM);
@@ -904,6 +892,14 @@ retry:
 
 	/* If the device is still connected, perform the scanning */
 	if (!test_bit(US_FLIDX_DISCONNECTING, &us->flags)) {
+
+		/* For bulk-only devices, determine the max LUN value */
+		if (us->protocol == US_PR_BULK &&
+				!(us->flags & US_FL_SINGLE_LUN)) {
+			down(&us->dev_semaphore);
+			us->max_lun = usb_stor_Bulk_max_lun(us);
+			up(&us->dev_semaphore);
+		}
 		scsi_scan_host(us_to_host(us));
 		printk(KERN_DEBUG "usb-storage: device scan complete\n");