sound: usb-audio: make the MotU Fastlane work again
Kernel 2.6.18 broke the MotU Fastlane, which uses duplicate endpoint
numbers in a manner that is not only illegal but also confuses the
kernel's endpoint descriptor caching mechanism. To work around this, we
have to add a separate usb_set_interface() call to guide the USB core to
the correct descriptors.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Reported-and-tested-by: David Fries <david@fries.net>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/usbmidi.c b/sound/usb/usbmidi.c
index 26bad37..2fb35cc 100644
--- a/sound/usb/usbmidi.c
+++ b/sound/usb/usbmidi.c
@@ -1778,8 +1778,18 @@
umidi->usb_protocol_ops = &snd_usbmidi_novation_ops;
err = snd_usbmidi_detect_per_port_endpoints(umidi, endpoints);
break;
- case QUIRK_MIDI_RAW:
+ case QUIRK_MIDI_FASTLANE:
umidi->usb_protocol_ops = &snd_usbmidi_raw_ops;
+ /*
+ * Interface 1 contains isochronous endpoints, but with the same
+ * numbers as in interface 0. Since it is interface 1 that the
+ * USB core has most recently seen, these descriptors are now
+ * associated with the endpoint numbers. This will foul up our
+ * attempts to submit bulk/interrupt URBs to the endpoints in
+ * interface 0, so we have to make sure that the USB core looks
+ * again at interface 0 by calling usb_set_interface() on it.
+ */
+ usb_set_interface(umidi->chip->dev, 0, 0);
err = snd_usbmidi_detect_per_port_endpoints(umidi, endpoints);
break;
case QUIRK_MIDI_EMAGIC: