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

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>
Cc: stable@vger.kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index 68e9f9a83fde8a0e255d9a32a1a15b1aee793e98..010094abf7521d0ad9336f0911fe7e229341156a 100644 (file)
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -2377,6 +2377,9 @@ 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 1a1e2e4df35e5809e7f7d81b405ca6dddf2f4311..c60a776e815d72f14b9b6345f2e8a0266f8ec1b6 100644 (file)
--- a/sound/usb/quirks-table.h
+++ b/sound/usb/quirks-table.h
@@ -2829,6 +2829,17 @@ 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 5ca80e7d30cd25bcc67cdf88509f46d39eec42e6..7016ad8981873ca046000d631ac112c12ed62dc1 100644 (file)
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -538,6 +538,7 @@ 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 15a12715bd05154bd9c0b4bbe7084f3df15022b2..b665d85555cb3aad0c9a621232f28d8e1f75344a 100644 (file)
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -95,6 +95,7 @@ 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,