[3.13.y-ckt stable] Patch "ALSA: usb-audio: prevent CH345 multiport output SysEx corruption" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt32.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 3372bcbdbe541f50111f7874e33963d506ced25b Mon Sep 17 00:00:00 2001
From: Clemens Ladisch <clemens at ladisch.de>
Date: Sun, 15 Nov 2015 22:38:29 +0100
Subject: 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 at ladisch.de>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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(+)

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index fa9028e..966051f 100644
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -2291,6 +2291,9 @@ int snd_usbmidi_create(struct snd_card *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;
diff --git a/sound/usb/quirks-table.h b/sound/usb/quirks-table.h
index e3bd28a..e5b9ade 100644
--- a/sound/usb/quirks-table.h
+++ b/sound/usb/quirks-table.h
@@ -2814,6 +2814,17 @@ 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 3fbb455..c3af0ce 100644
--- 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 5d2fe05..e5b2c30 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -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,
--
1.9.1