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>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index d09088727e5fa1d3b7a470686616759c9fed64d4..3f1838732b954d2531192b2205bc28f139844b8b 100644 (file)
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -2292,6 +2292,9 @@ 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 7c24088bcaa4a76423990da01d4371ba38099fdf..c600d4277974e18ee1acc0d3a4a2f6f6bc62762b 100644 (file)
--- a/sound/usb/quirks-table.h
+++ b/sound/usb/quirks-table.h
@@ -2875,6 +2875,17 @@ 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 337067cce25131920b0342b1ff35f254fc414c98..a9945fd050dea5b1d59f120ad461dc1c9a681ee6 100644 (file)
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -526,6 +526,7 @@ 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,