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 13a27e66e17926935bb1627ea37c88a29010121d..736783b9d1a2dddc2e49f7674b6ab72811b7f821 100644 (file)
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -2215,6 +2215,9 @@ 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 45d586b6e8b533f817d9744fd2910a3b2df7993d..9ec5ce4e35fb1bbc37d54a071d4361d965af449d 100644 (file)
--- a/sound/usb/quirks-table.h
+++ b/sound/usb/quirks-table.h
@@ -3041,6 +3041,17 @@ 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 734c6579b1946c92b858d2f89ce43635dc3f69c6..94cd28c2bd8d561ae6c72a00896d14d14afce48d 100644 (file)
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -313,6 +313,7 @@ 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 bc43bcaddf4d5ade6c4c32794c324c565b7ab7ff..d6f3fefc882f29e29c0c285e21f746e1a8f903c1 100644 (file)
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -83,6 +83,7 @@ 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,