USB: storage: Never reset devices that will morph to an old mode

Some devices must be switched to a new mode to fully use them.
A reset would make them revert to the old mode. Therefore a reset
must not be used for error handling with such devices.
Signed-off-by: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/quirks.c

@@ -120,6 +120,7 @@ void usb_detect_quirks(struct usb_device *udev)
 	 * for all devices.  It will affect things like hub resets
 	 * and EMF-related port disables.
 	 */
-	udev->persist_enabled = 1;
+	if (!(udev->quirks & USB_QUIRK_RESET_MORPHS))
+		udev->persist_enabled = 1;
 #endif	/* CONFIG_PM */
 }

drivers/usb/storage/transport.c

@@ -47,6 +47,8 @@
 #include <linux/errno.h>
 #include <linux/slab.h>
 
+#include <linux/usb/quirks.h>
+
 #include <scsi/scsi.h>
 #include <scsi/scsi_eh.h>
 #include <scsi/scsi_device.h>
@@ -1297,6 +1299,10 @@ int usb_stor_port_reset(struct us_data *us)
 {
 	int result;
 
+	/*for these devices we must use the class specific method */
+	if (us->pusb_dev->quirks & USB_QUIRK_RESET_MORPHS)
+		return -EPERM;
+
 	result = usb_lock_device_for_reset(us->pusb_dev, us->pusb_intf);
 	if (result < 0)
 		US_DEBUGP("unable to lock device for reset: %d\n", result);

include/linux/usb/quirks.h

@@ -19,4 +19,7 @@
 /* device can't handle its Configuration or Interface strings */
 #define USB_QUIRK_CONFIG_INTF_STRINGS	0x00000008
 
+/*device will morph if reset, don't use reset for handling errors */
+#define USB_QUIRK_RESET_MORPHS		0x00000010
+
 #endif /* __LINUX_USB_QUIRKS_H */