Commit b876aef7 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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[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: default avatarAlan Stern <>
Signed-off-by: default avatarMatthew Dharm <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 423e489d
......@@ -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,
......@@ -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 */
/* 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) {
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)
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)) {
us->max_lun = usb_stor_Bulk_max_lun(us);
printk(KERN_DEBUG "usb-storage: device scan complete\n");
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