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USB: disable reset-resume when USB_QUIRK_RESET is set

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The USB_QUIRK_RESET flag indicates that a USB device changes its
identity in some way when it is reset.  It may lose its firmware, its
descriptors may change, or it may switch back to a default mode of
operation.

If a device does this, the kernel needs to avoid resetting it.  Resets
are likely to fail, or worse, succeed while changing the device's
state in a way the system can't detect.

This means we should disable the reset-resume mechanism whenever this
quirk flag is present.  An attempted reset-resume will fail, the
device will be logically disconnected, and later on the hub driver
will rediscover and re-enumerate the device.  This will cause the
appropriate udev events to be generated, so that userspace will have a
chance to switch the device into its normal operating mode, if
necessary.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Oliver Neukum <oliver@neukum.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alan Stern 2014-03-18 10:39:05 -04:00 committed by Greg Kroah-Hartman
parent 6aec044cc2
commit 1d10255c1c
1 changed files with 12 additions and 2 deletions
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14
drivers/usb/core/hub.c
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@ -3105,9 +3105,19 @@ static int finish_port_resume(struct usb_device *udev)
* operation is carried out here, after the port has been
* resumed.
*/
if (udev->reset_resume)
if (udev->reset_resume) {
/*
* If the device morphs or switches modes when it is reset,
* we don't want to perform a reset-resume. We'll fail the
* resume, which will cause a logical disconnect, and then
* the device will be rediscovered.
*/
retry_reset_resume:
status = usb_reset_and_verify_device(udev);
if (udev->quirks & USB_QUIRK_RESET)
status = -ENODEV;
else
status = usb_reset_and_verify_device(udev);
}
/* 10.5.4.5 says be sure devices in the tree are still there.
* For now let's assume the device didn't go crazy on resume,