[alsa-devel] [PATCH v2 0/2] USB audio fixes

[Takashi Iwai]

On Sat, 15 Aug 2015 00:19:41 +0200,
Pierre-Louis Bossart wrote:
> 
> While trying to understand how asynchronous endpoints are supported, I
> identified two major issues. On my M-Audio transit, the following
> script tries to play using the 3 different endpoints supported and
> fails (error and no audio) after the first playback without the
> patches. With the patches on top of 4.1.5 or Takashi's for-next
> (4.2.0-rc5), I stopped the audio after an hour.
> 
> while true
> do
>     aplay -d5 -Dhw:2,0 ~/16_48.wav # play 48kHz, 16 bit on async ep
>     aplay -d5 -Dhw:2,0 ~/24_48.wav # play 48kHz, 24 bit on 'none'/async ep
>     aplay -d5 -Dhw:2,0 ~/24_96.wav # play 96 kHz, 24 bit on adaptive ep
>     aplay -d5 -Dhw:2,0 ~/24_48.wav 
>     aplay -d5 -Dhw:2,0 ~/16_48.wav
>     aplay -d5 -Dhw:2,0 ~/24_96.wav
> done
> 
> The first issue is pretty bad with corrupted pointers. When
> transitioning from a alternate setting with a sync_endpoint to another
> which doesn't have one by construction (synchronous, adaptive, async
> on capture), the pointers are not reset and the code tries to set the
> parameters of a non-existent endpoint.
> 
> The second issue is that the M-audio Transit descriptors are illegal
> but the logic can be changed without harm.
> 
> I sometimes hear noise on playback start, probably the code needs to
> be changed to add enough silent samples to let the PLL lock. I haven't
> had time to work on this and this is more of an enhancement.
> 
> v2: applied Takashi's comments
>     unconditional clean-up of sync_endpoint pointers
>     better logical tests and removal of goto
> 
> Pierre-Louis Bossart (2):
>   ALSA: usb: fix corrupted pointers due to interface setting change
>   ALSA: usb: handle descriptor with SYNC_NONE illegal value

Applied both now.  Thanks.


Takashi