Re: [alsa-devel] [PATCH] ALSA: ASoC: move dma_data from snd_soc_dai to snd_soc_pcm_stream

19 Mar 2010

Hello,
On Thursday 18 March 2010 21:23:58 ext Daniel Mack wrote:
...
This fixes a memory corruption when ASoC devices are used in
full-duplex mode. Specifically for pxa-ssp code, where this pointer
is dynamically allocated for each direction and destroyed upon each
stream start.
All other platforms are fixed blindly, I couldn't even compile-test
them. Sorry for any breakage I may have caused.
At least the OMAP code should not be affected by the bug, that you have with the 
pxa-ssp. I think the bug could be also fixed within the pxa code, since the 
whole thing goes down to inconsistent memory management within the pxa code.
Having said that, I do think having separate dma_data for each streams is a 
really good idea.
One thing that I can think of in OMAP case, where this could fix a nasty race 
condition is (have never seen it, but it is in theory possible):
Also in duplex case, when the second hw_param gets called after the first 
omap_mcbsp_hw_params, and before the omap_pcm_hw_params for the first stream.
The second omap_mcbsp_hw_params will override the dma_data, thus we would set 
bogus parameters for the first stream.
I do have comment however (down).
For the omap-mcbsp.c and omap-pcm.c changes:
Acked-by: Peter Ujfalusi peter.ujfalusi@nokia.com
..
...
b/sound/soc/atmel/atmel_ssc_dai.c index e588e63..0b59806 100644
--- a/sound/soc/atmel/atmel_ssc_dai.c
+++ b/sound/soc/atmel/atmel_ssc_dai.c
@@ -363,12 +363,12 @@ static int atmel_ssc_hw_params(struct
snd_pcm_substream *substream, ssc_p->dma_params[dir] = dma_params;
    /*


   * The cpu_dai->dma_data field is only used to communicate the


   * appropriate DMA parameters to the pcm driver hw_params()




   * The snd_soc_pcm_stream->dma_data field is only used to



communicate +        * the appropriate DMA parameters to the pcm driver
hw_params() * function.  It should not be used for other purposes
         * as it is common to all substreams.
         */

  rtd->dai->cpu_dai->dma_data = dma_params;




  snd_soc_dai_set_dma_data(rtd->dai->cpu_dai, substream, dma_params);

  channels = params_channels(params);

diff --git a/sound/soc/davinci/davinci-i2s.c
b/sound/soc/davinci/davinci-i2s.c index 6362ca0..4aad7ec 100644
--- a/sound/soc/davinci/davinci-i2s.c
+++ b/sound/soc/davinci/davinci-i2s.c
@@ -585,7 +585,8 @@ static int davinci_i2s_probe(struct platform_device
*pdev) dev->dma_params[SNDRV_PCM_STREAM_CAPTURE].channel = res->start;
    davinci_i2s_dai.private_data = dev;


  davinci_i2s_dai.dma_data = dev->dma_params;




  davinci_i2s_dai.capture.dma_data = dev->dma_params;


  davinci_i2s_dai.playback.dma_data = dev->dma_params;



Would not be more consistent around the places to actually use the
    	snd_soc_dai_set_dma_data(...);
function instead of direct assignment here, and there randomly?
...
    ret = snd_soc_register_dai(&davinci_i2s_dai);
    if (ret != 0)
            goto err_free_mem;

-- 
Péter

    