USB: disable reset-resume when USB_QUIRK_RESET is set

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 <[email protected]>
CC: Oliver Neukum <[email protected]>
Reviewed-by: Hans de Goede <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/usb/core/hub.c

@@ -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,