[PATCH 0/3] various USB MIDI workarounds

[PATCH 0/3] various USB MIDI workarounds

[Clemens Ladisch]

Just a bunch of MIDI quirks, with various degrees of quirkiness.

 sound/usb/midi.c         |   46 +++++++++++++++++++++++++++++++++++++++
 sound/usb/quirks-table.h |   11 +++++++++
 sound/usb/quirks.c       |    1
 sound/usb/usbaudio.h     |    1
 4 files changed, 59 insertions(+)

[PATCH 1/3] ALSA: usb-audio: add packet size quirk for the Medeli DD305

[Clemens Ladisch]

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
---
 sound/usb/midi.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index 7661616..68e9f9a 100644
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -1341,6 +1341,7 @@ static int snd_usbmidi_out_endpoint_create(struct snd_usb_midi *umidi,
 		 * Various chips declare a packet size larger than 4 bytes, but
 		 * do not actually work with larger packets:
 		 */
+	case USB_ID(0x0a67, 0x5011): /* Medeli DD305 */
 	case USB_ID(0x0a92, 0x1020): /* ESI M4U */
 	case USB_ID(0x1430, 0x474b): /* RedOctane GH MIDI INTERFACE */
 	case USB_ID(0x15ca, 0x0101): /* Textech USB Midi Cable */

[PATCH 2/3] ALSA: usb-audio: prevent CH345 multiport output SysEx corruption

[Clemens Ladisch]

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>
Cc: stable@vger.kernel.org
---
 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 68e9f9a..010094a 100644
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -2379,6 +2379,9 @@ 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:
 		dev_err(&umidi->dev->dev, "invalid quirk type %d\n",
 			quirk->type);
diff --git a/sound/usb/quirks-table.h b/sound/usb/quirks-table.h
index 1a1e2e4..c60a776 100644
--- a/sound/usb/quirks-table.h
+++ b/sound/usb/quirks-table.h
@@ -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),
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index 75a9d4b..f529102 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -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,
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 15a1271..b665d85 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -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,

[PATCH 3/3] ALSA: usb-audio: work around CH345 input SysEx corruption

[Clemens Ladisch]

One of the many faults of the QinHeng CH345 USB MIDI interface chip is
that it does not handle received SysEx messages correctly -- every second
event packet has a wrong code index number, which is the one from the last
seen message, instead of 4.  For example, the two messages "FE F0 01 02 03
04 05 06 07 08 09 0A 0B 0C 0D 0E F7" result in the following event
packets:

correct:       CH345:
0F FE 00 00    0F FE 00 00
04 F0 01 02    04 F0 01 02
04 03 04 05    0F 03 04 05
04 06 07 08    04 06 07 08
04 09 0A 0B    0F 09 0A 0B
04 0C 0D 0E    04 0C 0D 0E
05 F7 00 00    05 F7 00 00

A class-compliant driver must interpret an event packet with CIN 15 as
having a single data byte, so the other two bytes would be ignored.  The
message received by the host would then be missing two bytes out of six;
in this example, "F0 01 02 03 06 07 08 09 0C 0D 0E F7".

These corrupted SysEx event packages contain only data bytes, while the
CH345 uses event packets with a correct CIN value only for messages with
a status byte, so it is possible to distinguish between these two cases by
checking for the presence of this status byte.

(Other bugs in the CH345's input handling, such as the corruption resulting
from running status, cannot be worked around.)

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Cc: stable@vger.kernel.org
---
 sound/usb/midi.c |   42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index 010094a..5b4c58c 100644
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -174,6 +174,8 @@ struct snd_usb_midi_in_endpoint {
 		u8 running_status_length;
 	} ports[0x10];
 	u8 seen_f5;
+	bool in_sysex;
+	u8 last_cin;
 	u8 error_resubmit;
 	int current_port;
 };
@@ -468,6 +470,39 @@ static void snd_usbmidi_maudio_broken_running_status_input(
 }

 /*
+ * QinHeng CH345 is buggy: every second packet inside a SysEx has not CIN 4
+ * but the previously seen CIN, but still with three data bytes.
+ */
+static void ch345_broken_sysex_input(struct snd_usb_midi_in_endpoint *ep,
+				     uint8_t *buffer, int buffer_length)
+{
+	unsigned int i, cin, length;
+
+	for (i = 0; i + 3 < buffer_length; i += 4) {
+		if (buffer[i] == 0 && i > 0)
+			break;
+		cin = buffer[i] & 0x0f;
+		if (ep->in_sysex &&
+		    cin == ep->last_cin &&
+		    (buffer[i + 1 + (cin == 0x6)] & 0x80) == 0)
+			cin = 0x4;
+#if 0
+		if (buffer[i + 1] == 0x90) {
+			/*
+			 * Either a corrupted running status or a real note-on
+			 * message; impossible to detect reliably.
+			 */
+		}
+#endif
+		length = snd_usbmidi_cin_length[cin];
+		snd_usbmidi_input_data(ep, 0, &buffer[i + 1], length);
+		ep->in_sysex = cin == 0x4;
+		if (!ep->in_sysex)
+			ep->last_cin = cin;
+	}
+}
+
+/*
  * CME protocol: like the standard protocol, but SysEx commands are sent as a
  * single USB packet preceded by a 0x0F byte.
  */
@@ -660,6 +695,12 @@ static struct usb_protocol_ops snd_usbmidi_cme_ops = {
 	.output_packet = snd_usbmidi_output_standard_packet,
 };

+static struct usb_protocol_ops snd_usbmidi_ch345_broken_sysex_ops = {
+	.input = ch345_broken_sysex_input,
+	.output = snd_usbmidi_standard_output,
+	.output_packet = snd_usbmidi_output_standard_packet,
+};
+
 /*
  * AKAI MPD16 protocol:
  *
@@ -2380,6 +2421,7 @@ int snd_usbmidi_create(struct snd_card *card,
 		err = snd_usbmidi_detect_per_port_endpoints(umidi, endpoints);
 		break;
 	case QUIRK_MIDI_CH345:
+		umidi->usb_protocol_ops = &snd_usbmidi_ch345_broken_sysex_ops;
 		err = snd_usbmidi_detect_per_port_endpoints(umidi, endpoints);
 		break;
 	default:

Re: [PATCH 0/3] various USB MIDI workarounds

[Takashi Iwai]

On Sun, 15 Nov 2015 22:36:45 +0100,
Clemens Ladisch wrote:
> 
> Just a bunch of MIDI quirks, with various degrees of quirkiness.
> 
>  sound/usb/midi.c         |   46 +++++++++++++++++++++++++++++++++++++++
>  sound/usb/quirks-table.h |   11 +++++++++
>  sound/usb/quirks.c       |    1
>  sound/usb/usbaudio.h     |    1
>  4 files changed, 59 insertions(+)

Applied all three patches (with Cc to stable to the first one, too).
Thanks.


Takashi