From 96c9346aee41d4fb14fa0ab6fdd81b187f496311 Mon Sep 17 00:00:00 2001 From: Clemens Ladisch 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 Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/usb/usbaudio.h | 1 + 1 file changed, 1 insertion(+) (limited to 'sound/usb/usbaudio.h') diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h index 91d0380431b4..991aa84491cd 100644 --- a/sound/usb/usbaudio.h +++ b/sound/usb/usbaudio.h @@ -94,6 +94,7 @@ 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, -- cgit v1.2.3