[PATCH] PATCH: usb-storage: move GetMaxLUN later in time (b876aef7) · Commits · 戴 / test

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

+1 −0

Original line number	Diff line number	Diff line
		@@ -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

+13 −17

Original line number	Diff line number	Diff line
		@@ -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");

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