[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>
diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index 5164900..92ee079 100644
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -747,25 +747,13 @@
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 @@
/* 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");