Re: [alsa-devel] [PATCH 1/2] ASoC: Allow drivers to specify how many bits are significant on a DAI

On 01/16/2012 07:41 PM, Mark Brown wrote:

/*

• • List of sample sizes that might go over the bus for parameter
• • application. There ought to be a wildcard sample size for things
• • like the DAC/ADC resolution to use but there isn't right now.
• */

+static int sample_sizes[] = {

• 8, 16, 24, 32,

+};

+static void soc_pcm_apply_msb(struct snd_pcm_substream *substream,

• 	      struct snd_soc_dai *dai)
  

+{

• int ret, i, bits;
• if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)

• bits = dai->driver->playback.sig_bits;
  

• else

• bits = dai->driver->capture.sig_bits;
  

• if (!bits)

• return;
  

• for (i = 0; i < ARRAY_SIZE(sample_sizes); i++) {

• ret = snd_pcm_hw_constraint_msbits(substream->runtime,
  

• 				   0, sample_sizes[i],
  

• 				   bits);
  

Should we apply the constraint only if the sample size is bigger than the msbit request: if (sample_sizes[i] > bits) { ret = snd_pcm_hw_constraint_msbits(); }

Might be not an issue to say that we have 24msbit on the 8bit sample, but it does not sound right.

• if (ret != 0)
  

• 	dev_warn(dai->dev,
  

• 		 "Failed to set MSB %d/%d: %d\n",
  

• 		 bits, sample_sizes[i], ret);
  

• }

+}

+/*

• Called by ALSA when a PCM substream is opened, the runtime->hw record is
• then initialized and any private data can be allocated. This also calls
• startup for the cpu DAI, platform, machine and codec DAI.

@@ -187,6 +220,9 @@ static int soc_pcm_open(struct snd_pcm_substream *substream) goto config_err; }

• soc_pcm_apply_msb(substream, codec_dai);
• soc_pcm_apply_msb(substream, cpu_dai);
• /* Symmetry only applies if we've already got an active stream. */ if (cpu_dai->active) { ret = soc_pcm_apply_symmetry(substream, cpu_dai);