[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>

2 files changed, 14 insertions, 17 deletions

diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c
index c1ba5301ebfc..e89e945fc4a7 100644
--- a/drivers/usb/storage/transport.c
+++ b/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 | 
diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index 5164900e40c1..92ee079d9172 100644
--- a/drivers/usb/storage/usb.c
+++ b/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");