ALSA: Add support for wildcard msbits constraints (8ef9df55) · Commits · 戴 / test

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>

sound/core/pcm_lib.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -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,

Admin message