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From: Qais Yousef <>
To: Mark Brown <>
Cc: <>, Vinod Koul <>,
	"Liam Girdwood" <>,
	Jaroslav Kysela <>, "Takashi Iwai" <>,
Subject: Re: [PATCH] ALSA: ASoC: soc-compress.c: fix NULL dereference
Date: Fri, 2 Jan 2015 09:07:32 +0000	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 12/29/2014 04:13 PM, Mark Brown wrote:
> On Tue, Dec 23, 2014 at 09:09:27AM +0000, Qais Yousef wrote:
>> In soc_new_compress() when rtd->dai_link->daynmic is set, we create the pcm
>> substreams with this call:
>>     ret = snd_pcm_new_internal(rtd->card->snd_card, new_name, num,
>>                                     1, 0, &be_pcm);
>> which passes 0 as capture_count leading to
>>     be_pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream
>> being NULL, hence when trying to set rtd a few lines below we get an oops.
>> Fix by removing this line of code since CAPTURE substream will always be NULL.
> Why will the capture stream always be NULL?  There should be no
> intrinsic reason why we can't have hardware support for capturing
> compressed audio.

I think because we pass 0 as capture_count in snd_pcm_new_internal(). If 
I read the code correctly this will lead to _snd_pcm_new() to be called 
which in return will call snd_pcm_new_stream(pcm, 
SNDRV_PCM_STREAM_CAPTURE, capture_count) which will cause no substream 
to be allocated for the capture case, hence being NULL. I get an oops in 
my experimental driver when I set dynamic = 1 in FE dai link. If I did 
something wrong there that caused this, it's not obvious to me how.

Maybe a better fix would be to replace the 1 and 0 in 
snd_pcm_new_internal() call with rtd->dai_link->dpcm_playback and 

      reply	other threads:[~2015-01-02  9:07 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-23  9:09 Qais Yousef
2014-12-29 16:13 ` Mark Brown
2015-01-02  9:07   ` Qais Yousef [this message]

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