ALSA: usb-audio: prevent CH345 multiport output SysEx corruption

commit 1ca8b201309d842642f221db7f02f71c0af5be2d upstream.

The CH345 USB MIDI chip has two output ports.  However, they are
multiplexed through one pin, and the number of ports cannot be reduced
even for hardware that implements only one connector, so for those
devices, data sent to either port ends up on the same hardware output.
This becomes a problem when both ports are used at the same time, as
longer MIDI commands (such as SysEx messages) are likely to be
interrupted by messages from the other port, and thus to get lost.

It would not be possible for the driver to detect how many ports the
device actually has, except that in practice, _all_ devices built with
the CH345 have only one port.  So we can just ignore the device's
descriptors, and hardcode one output port.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index 4bed82c70256b9d10e2e3d151196fa02e2237824..5010aadb2534ffc627f9cacea2b1d833e41347d7 100644 (file)
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -2374,6 +2374,9 @@ int snd_usbmidi_create(struct snd_card *card,
                if (err < 0)
                        break;
 
+               err = snd_usbmidi_detect_per_port_endpoints(umidi, endpoints);
+               break;
+       case QUIRK_MIDI_CH345:
                err = snd_usbmidi_detect_per_port_endpoints(umidi, endpoints);
                break;
        default:

diff --git a/sound/usb/quirks-table.h b/sound/usb/quirks-table.h
index e4756651a52c8873457ae340450934dcfbd5dfad..ecc2a4ea014d2ac049c651945054ac24d0584b73 100644 (file)
--- a/sound/usb/quirks-table.h
+++ b/sound/usb/quirks-table.h
@@ -2820,6 +2820,17 @@ YAMAHA_DEVICE(0x7010, "UB99"),
        .idProduct = 0x1020,
 },
 
+/* QinHeng devices */
+{
+       USB_DEVICE(0x1a86, 0x752d),
+       .driver_info = (unsigned long) &(const struct snd_usb_audio_quirk) {
+               .vendor_name = "QinHeng",
+               .product_name = "CH345",
+               .ifnum = 1,
+               .type = QUIRK_MIDI_CH345
+       }
+},
+
 /* KeithMcMillen Stringport */
 {
        USB_DEVICE(0x1f38, 0x0001),

diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index 528fa6e48293f4f8e25196fd5427f55d83bd20db..eef9b8e4b9498883a7ff843f7c7e124e3b1970a1 100644 (file)
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -535,6 +535,7 @@ int snd_usb_create_quirk(struct snd_usb_audio *chip,
                [QUIRK_MIDI_CME] = create_any_midi_quirk,
                [QUIRK_MIDI_AKAI] = create_any_midi_quirk,
                [QUIRK_MIDI_FTDI] = create_any_midi_quirk,
+               [QUIRK_MIDI_CH345] = create_any_midi_quirk,
                [QUIRK_AUDIO_STANDARD_INTERFACE] = create_standard_audio_quirk,
                [QUIRK_AUDIO_FIXED_ENDPOINT] = create_fixed_stream_quirk,
                [QUIRK_AUDIO_EDIROL_UAXX] = create_uaxx_quirk,

diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 91d0380431b4f79f1e209cd973b7f44152caa494..991aa84491cd057b680c76d1ece07292fbc2d42d 100644 (file)
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -94,6 +94,7 @@ enum quirk_type {
        QUIRK_MIDI_AKAI,
        QUIRK_MIDI_US122L,
        QUIRK_MIDI_FTDI,
+       QUIRK_MIDI_CH345,
        QUIRK_AUDIO_STANDARD_INTERFACE,
        QUIRK_AUDIO_FIXED_ENDPOINT,
        QUIRK_AUDIO_EDIROL_UAXX,