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Commit d05cc104 authored by Clemens Ladisch's avatar Clemens Ladisch Committed by Jaroslav Kysela
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[ALSA] usb-audio: work around broken M-Audio MidiSport Uno firmware 



The firmware of the M-Audio USB Uno MIDI Interface has, at least in
hardware revision 1.25, a bug that garbles its USB output.  When it
receives a Note On MIDI message that uses running status, the resulting
USB MIDI packet has a wrong CIN (4 instead of 9) and a wrong length
(2 bytes, the status byte is still missing).
This patch adds a workaround to track the CINs and the MIDI messages of
received USB MIDI packets to detect whether a packet with CIN 4 is a
correct SysEx packet or a buggy running status packet.

Signed-off-by: default avatarClemens Ladisch <clemens@ladisch.de>
Signed-off-by: default avatarJaroslav Kysela <perex@suse.cz>
parent a9121458

sound/usb/usbmidi.c

+51 −1
Original line number Diff line number Diff line 
/*

 * usbmidi.c - ALSA USB MIDI driver

 *

 * Copyright (c) 2002-2005 Clemens Ladisch

 * Copyright (c) 2002-2007 Clemens Ladisch

 * All rights reserved.

 *

 * Based on the OSS usb-midi driver by NAGANO Daisuke,
@@ -145,6 +145,7 @@ struct snd_usb_midi_in_endpoint { 
	struct urb* urb;

	struct usbmidi_in_port {

		struct snd_rawmidi_substream *substream;

		u8 running_status_length;

	} ports[0x10];

	u8 seen_f5;

	u8 error_resubmit;
@@ -365,6 +366,46 @@ static void snd_usbmidi_midiman_input(struct snd_usb_midi_in_endpoint* ep, 
		}

}



/*

 * Buggy M-Audio device: running status on input results in a packet that has

 * the data bytes but not the status byte and that is marked with CIN 4.

 */

static void snd_usbmidi_maudio_broken_running_status_input(

					struct snd_usb_midi_in_endpoint* ep,

					uint8_t* buffer, int buffer_length)

{

	int i;



	for (i = 0; i + 3 < buffer_length; i += 4)

		if (buffer[i] != 0) {

			int cable = buffer[i] >> 4;

			u8 cin = buffer[i] & 0x0f;

			struct usbmidi_in_port *port = &ep->ports[cable];

			int length;

			

			length = snd_usbmidi_cin_length[cin];

			if (cin == 0xf && buffer[i + 1] >= 0xf8)

				; /* realtime msg: no running status change */

			else if (cin >= 0x8 && cin <= 0xe)

				/* channel msg */

				port->running_status_length = length - 1;

			else if (cin == 0x4 &&

				 port->running_status_length != 0 &&

				 buffer[i + 1] < 0x80)

				/* CIN 4 that is not a SysEx */

				length = port->running_status_length;

			else

				/*

				 * All other msgs cannot begin running status.

				 * (A channel msg sent as two or three CIN 0xF

				 * packets could in theory, but this device

				 * doesn't use this format.)

				 */

				port->running_status_length = 0;

			snd_usbmidi_input_data(ep, cable, &buffer[i + 1], length);

		}

}



/*

 * Adds one USB MIDI packet to the output buffer.

 */
@@ -525,6 +566,12 @@ static struct usb_protocol_ops snd_usbmidi_midiman_ops = { 
	.output_packet = snd_usbmidi_output_midiman_packet,

};



static struct usb_protocol_ops snd_usbmidi_maudio_broken_running_status_ops = {

	.input = snd_usbmidi_maudio_broken_running_status_input,

	.output = snd_usbmidi_standard_output, 

	.output_packet = snd_usbmidi_output_standard_packet,

};



/*

 * Novation USB MIDI protocol: number of data bytes is in the first byte

 * (when receiving) (+1!) or in the second byte (when sending); data begins
@@ -1606,6 +1653,9 @@ int snd_usb_create_midi_interface(struct snd_usb_audio* chip, 
	switch (quirk ? quirk->type : QUIRK_MIDI_STANDARD_INTERFACE) {

	case QUIRK_MIDI_STANDARD_INTERFACE:

		err = snd_usbmidi_get_ms_info(umidi, endpoints);

		if (chip->usb_id == USB_ID(0x0763, 0x0150)) /* M-Audio Uno */

			umidi->usb_protocol_ops =

				&snd_usbmidi_maudio_broken_running_status_ops;

		break;

	case QUIRK_MIDI_FIXED_ENDPOINT:

		memcpy(&endpoints[0], quirk->data,