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ALSA: Add support for wildcard msbits constraints 

Currently the msbits constraints requires to specify a specific sample
format width for which the constraint should be applied. But often the
number of most significant bits is not sample format specific, but rather a
absolute limit. E.g. the PCM interface might accept 32-bit and 24-bit
samples, but the DAC has a 16-bit resolution and throws away the LSBs. In
this case for both 32-bit and 24-bit format msbits should be set to 16. This
patch extends snd_pcm_hw_constraint_msbits() so that a wildcard constraint
can be setup that is applied for all formats with a sample width larger than
the specified msbits. Choosing the wildcard constraint is done by setting
the sample width parameter of the function to 0.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Lars-Peter Clausen 2014-12-29 18:43:37 +01:00 committed by Takashi Iwai
parent 19f52fae5a
commit 8ef9df55a7
1 changed files with 12 additions and 1 deletions
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13
sound/core/pcm_lib.c
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@ -1299,8 +1299,14 @@ static int snd_pcm_hw_rule_msbits(struct snd_pcm_hw_params *params,
int width = l & 0xffff;
unsigned int msbits = l >> 16;
struct snd_interval *i = hw_param_interval(params, SNDRV_PCM_HW_PARAM_SAMPLE_BITS);
if (snd_interval_single(i) && snd_interval_value(i) == width)
if (!snd_interval_single(i))
return 0;
if ((snd_interval_value(i) == width) ||
(width == 0 && snd_interval_value(i) > msbits))
params->msbits = min_not_zero(params->msbits, msbits);
return 0;
}
@ -1311,6 +1317,11 @@ static int snd_pcm_hw_rule_msbits(struct snd_pcm_hw_params *params,
* @width: sample bits width
* @msbits: msbits width
*
* This constraint will set the number of most significant bits (msbits) if a
* sample format with the specified width has been select. If width is set to 0
* the msbits will be set for any sample format with a width larger than the
* specified msbits.
*
* Return: Zero if successful, or a negative error code on failure.
*/
int snd_pcm_hw_constraint_msbits(struct snd_pcm_runtime *runtime,