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: Ben Hutchings <ben@decadent.org.uk>

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index 11d324aea1416e20a3f1373ce51bef2b670360b2..01c498241a0f7f22af5b11892db88ba22e61beb4 100644 (file)
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -2213,6 +2213,9 @@ 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 c014f004a0f1316189aae3b7ba7b16d593510908..0f18c753e660eedaa1ac8c92d5145af9ac703d6d 100644 (file)
--- a/sound/usb/quirks-table.h
+++ b/sound/usb/quirks-table.h
@@ -2611,6 +2611,17 @@ 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 9c82f8b67a61f71b2117f3a7c414feedd414bedd..b01d3cf3759ed171f5300e15295a4713245b5a87 100644 (file)
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -311,6 +311,7 @@ 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 6c805a51d7d79e7064e8abeb51f0363c25428a77..5e0e58adfcdbc013eac6558117de8d284c4452f9 100644 (file)
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -81,6 +81,7 @@ 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,