Commit 1ca8b201 authored by Clemens Ladisch's avatar Clemens Ladisch Committed by Takashi Iwai
Browse files

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: default avatarClemens Ladisch <clemens@ladisch.de>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 98d362be

sound/usb/midi.c

+3 −0
Original line number Diff line number Diff line
@@ -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:

sound/usb/quirks-table.h

+11 −0
Original line number Diff line number Diff line
@@ -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),

sound/usb/quirks.c

+1 −0
Original line number Diff line number Diff line
@@ -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,

sound/usb/usbaudio.h

+1 −0
Original line number Diff line number Diff line
@@ -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,

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