Patch "ALSA: usb-audio: prevent CH345 multiport output SysEx corruption" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
alsa-usb-audio-prevent-ch345-multiport-output-sysex-corruption.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Clemens Ladisch <[email protected]>
Date: Sun, 15 Nov 2015 22:38:29 +0100
Subject: ALSA: usb-audio: prevent CH345 multiport output SysEx corruption

From: Clemens Ladisch <[email protected]>

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.

---
 sound/usb/midi.c         |    3 +++
 sound/usb/quirks-table.h |   11 +++++++++++
 sound/usb/quirks.c       |    1 +
 sound/usb/usbaudio.h     |    1 +
 4 files changed, 16 insertions(+)

@@ -2291,6 +2291,9 @@ int snd_usbmidi_create(struct snd_card *
 
 		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:
 		snd_printd(KERN_ERR "invalid quirk type %d\n", quirk->type);
 		err = -ENXIO;

@@ -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),

@@ -526,6 +526,7 @@ int snd_usb_create_quirk(struct snd_usb_
 		[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,

@@ -84,6 +84,7 @@ 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,

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/alsa-usb-audio-work-around-ch345-input-sysex-corruption.patch queue-3.14/alsa-usb-audio-prevent-ch345-multiport-output-sysex-corruption.patch queue-3.14/alsa-usb-audio-add-packet-size-quirk-for-the-medeli-dd305.patch