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>

4 files changed, 14 insertions, 4 deletions

diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 823296d7d57..a6b88482637 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -3347,7 +3347,7 @@ static int snd_usb_create_quirk(struct snd_usb_audio *chip,
                 [QUIRK_MIDI_YAMAHA] = snd_usb_create_midi_interface,
                 [QUIRK_MIDI_MIDIMAN] = snd_usb_create_midi_interface,
                 [QUIRK_MIDI_NOVATION] = snd_usb_create_midi_interface,
-                [QUIRK_MIDI_RAW] = snd_usb_create_midi_interface,
+                [QUIRK_MIDI_FASTLANE] = snd_usb_create_midi_interface,
                 [QUIRK_MIDI_EMAGIC] = snd_usb_create_midi_interface,
                 [QUIRK_MIDI_CME] = snd_usb_create_midi_interface,
                 [QUIRK_AUDIO_STANDARD_INTERFACE] = create_standard_audio_quirk,
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 36e4f7a29ad..8e7f78941ba 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -153,7 +153,7 @@ enum quirk_type {
         QUIRK_MIDI_YAMAHA,
         QUIRK_MIDI_MIDIMAN,
         QUIRK_MIDI_NOVATION,
-        QUIRK_MIDI_RAW,
+        QUIRK_MIDI_FASTLANE,
         QUIRK_MIDI_EMAGIC,
         QUIRK_MIDI_CME,
         QUIRK_MIDI_US122L,
diff --git a/sound/usb/usbmidi.c b/sound/usb/usbmidi.c
index 26bad373fe6..2fb35cc22a3 100644
--- a/sound/usb/usbmidi.c
+++ b/sound/usb/usbmidi.c
@@ -1778,8 +1778,18 @@ int snd_usb_create_midi_interface(struct snd_usb_audio* chip,
                 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:
diff --git a/sound/usb/usbquirks.h b/sound/usb/usbquirks.h
index 647ef502965..5d955aaad85 100644
--- a/sound/usb/usbquirks.h
+++ b/sound/usb/usbquirks.h
@@ -1868,7 +1868,7 @@ YAMAHA_DEVICE(0x7010, "UB99"),
                 .data = & (const struct snd_usb_audio_quirk[]) {
                         {
                                 .ifnum = 0,
-                                .type = QUIRK_MIDI_RAW
+                                .type = QUIRK_MIDI_FASTLANE
                         },
                         {
                                 .ifnum = 1,