[alsa-devel] [PATCH 1/2] ALSA: usb: fix corrupted pointers due to interface setting change

[Takashi Iwai]

On Fri, 14 Aug 2015 17:39:32 +0200,
Pierre-Louis Bossart wrote:
> 
> On 8/14/15 10:28 AM, Takashi Iwai wrote:
> > On Fri, 14 Aug 2015 17:03:10 +0200,
> > Takashi Iwai wrote:
> >>
> >> On Fri, 14 Aug 2015 00:42:32 +0200,
> >> Pierre-Louis Bossart wrote:
> >>>
> >>> When a transition occurs between alternate settings that do not use the
> >>> same synchronization method, the substream pointers were not reset.
> >>> This prevents audio from being played during the second transition.
> >>>
> >>> Identified and tested with M-Audio Transit device
> >>> (0763:2006 Midiman M-Audio Transit)
> >>
> >> Hmm, I have this old device, too, but couldn't reproduce the problem.
> >> Is there any special setup with it?
> >
> > OK, I could see it after switching a few times.  But, also your patch
> > didn't cure, either...
> 
> I tested this with Ubuntu 14.04 and the default madfuload package that 
> comes with it for the firmware.
> 
> I think you need both patches to get the device to work. I split the 
> patches in two since I think the second problem is device specific while 
> the first one is a generic one that can happen on other devices.

I tested both at once, of course :)
With my device, 24/96 -> 16/48 works, then again switching to 24/96
stalls.  After that, it doesn't work no matter which mode is until I
replug the device.


Takashi

> I generated three chirps test files with audacity, one stereo 96kHz 
> 24bits (3 bytes), one stereo 48kHz 24 bits (3 bytes) and then stereo 
> 48kHz 16 bits. This matches the capabilities of the three endpoints.
> If you try first with the 48kHz 16bits one then typically the others 
> won't work.
> 
> >
> >
> > Takashi
> >
> >>
> >>
> >> Takashi
> >>
> >>>
> >>> Details of the issue:
> >>>
> >>> First playback to adaptive endpoint:
> >>> $ aplay -Dhw:1,0 ~/24_96.wav
> >>> Playing WAVE '/home/plb/24_96.wav' : Signed 24 bit Little Endian in 3bytes,
> >>> Rate 96000 Hz, Stereo
> >>>
> >>> [ 3169.297556] usb 1-2: setting usb interface 1:1
> >>> [ 3169.297568] usb 1-2: Creating new playback data endpoint #3
> >>> [ 3169.298563] usb 1-2: Setting params for ep #3 (type 0, 3 urbs), ret=0
> >>> [ 3169.298574] usb 1-2: Starting data EP @ffff880035fc8000
> >>>
> >>> first playback to asynchronous endpoint:
> >>> $ aplay -Dhw:1,0 ~/16_48.wav
> >>> Playing WAVE '/home/plb/16_48.wav' : Signed 16 bit Little Endian,
> >>> Rate 48000 Hz, Stereo
> >>>
> >>> [ 3204.520251] usb 1-2: setting usb interface 1:3
> >>> [ 3204.520264] usb 1-2: Creating new playback data endpoint #3
> >>> [ 3204.520272] usb 1-2: Creating new capture sync endpoint #83
> >>> [ 3204.521162] usb 1-2: Setting params for ep #3 (type 0, 4 urbs), ret=0
> >>> [ 3204.521177] usb 1-2: Setting params for ep #83 (type 1, 4 urbs), ret=0
> >>> [ 3204.521182] usb 1-2: Starting data EP @ffff880035fce000
> >>> [ 3204.521204] usb 1-2: Starting sync EP @ffff8800bd616000
> >>>
> >>> second playback to adaptive endpoint: no audio and error on terminal:
> >>> $ aplay -Dhw:1,0 ~/24_96.wav
> >>> Playing WAVE '/home/plb/24_96.wav' : Signed 24 bit Little Endian in 3bytes,
> >>> Rate 96000 Hz, Stereo
> >>> aplay: pcm_write:1939: write error: Input/output error
> >>>
> >>> [ 3239.483589] usb 1-2: setting usb interface 1:1
> >>> [ 3239.483601] usb 1-2: Re-using EP 3 in iface 1,1 @ffff880035fc8000
> >>> [ 3239.484590] usb 1-2: Setting params for ep #3 (type 0, 4 urbs), ret=0
> >>> [ 3239.484606] usb 1-2: Setting params for ep #83 (type 1, 4 urbs), ret=0
> >>>
> >>> This last line shows that a sync endpoint is used when it shouldn't.
> >>> The sync endpoint is no longer valid and the pointers are corrupted
> >>>
> >>> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
> >>> ---
> >>>   sound/usb/pcm.c | 13 +++++++++++++
> >>>   1 file changed, 13 insertions(+)
> >>>
> >>> diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
> >>> index b4ef410..7cd7c03 100644
> >>> --- a/sound/usb/pcm.c
> >>> +++ b/sound/usb/pcm.c
> >>> @@ -395,6 +395,19 @@ static int set_sync_endpoint(struct snd_usb_substream *subs,
> >>>   	if (err < 0)
> >>>   		return err;
> >>>
> >>> +	if ((is_playback && (attr != USB_ENDPOINT_SYNC_ASYNC)) ||
> >>> +		(!is_playback && (attr != USB_ENDPOINT_SYNC_ADAPTIVE))) {
> >>> +
> >>> +		/*
> >>> +		 * Clean-up subs pointers to make sure sync_endpoint is never
> >>> +		 * configured. This is needed in case of a transition between
> >>> +		 * alternate settings using different synchronization modes
> >>> +		 * where the previous sync_endpoint may no longer be valid.
> >>> +		 */
> >>> +		subs->sync_endpoint = NULL;
> >>> +		subs->data_endpoint->sync_master = NULL;
> >>> +	}
> >>> +
> >>>   	if (altsd->bNumEndpoints < 2)
> >>>   		return 0;
> >>>
> >>> --
> >>> 1.9.1
> >>>
>