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Commit e3a9269f authored by Lars-Peter Clausen's avatar Lars-Peter Clausen Committed by Mark Brown
Browse files

ALSA: Add helper function for intersecting two rate masks 



A bit of special care is necessary when creating the intersection of two rate
masks. This comes from the special meaning of the SNDRV_PCM_RATE_CONTINUOUS and
SNDRV_PCM_RATE_KNOT bits, which needs special handling when intersecting two
rate masks. SNDRV_PCM_RATE_CONTINUOUS means the hardware supports all rates in a
specific interval. SNDRV_PCM_RATE_KNOT means the hardware supports a set of
discrete rates specified by a list constraint. For all other cases the supported
rates are specified directly in the rate mask.

Signed-off-by: default avatarLars-Peter Clausen <lars@metafoo.de>
Reviewed-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarMark Brown <broonie@linaro.org>
parent bf103eb4

include/sound/pcm.h

+2 −0
Original line number Diff line number Diff line
@@ -901,6 +901,8 @@ extern const struct snd_pcm_hw_constraint_list snd_pcm_known_rates; 
int snd_pcm_limit_hw_rates(struct snd_pcm_runtime *runtime);

unsigned int snd_pcm_rate_to_rate_bit(unsigned int rate);

unsigned int snd_pcm_rate_bit_to_rate(unsigned int rate_bit);

unsigned int snd_pcm_rate_mask_intersect(unsigned int rates_a,

					 unsigned int rates_b);



static inline void snd_pcm_set_runtime_buffer(struct snd_pcm_substream *substream,

					      struct snd_dma_buffer *bufp)

sound/core/pcm_misc.c

+39 −0
Original line number Diff line number Diff line
@@ -514,3 +514,42 @@ unsigned int snd_pcm_rate_bit_to_rate(unsigned int rate_bit) 
	return 0;

}

EXPORT_SYMBOL(snd_pcm_rate_bit_to_rate);



static unsigned int snd_pcm_rate_mask_sanitize(unsigned int rates)

{

	if (rates & SNDRV_PCM_RATE_CONTINUOUS)

		return SNDRV_PCM_RATE_CONTINUOUS;

	else if (rates & SNDRV_PCM_RATE_KNOT)

		return SNDRV_PCM_RATE_KNOT;

	return rates;

}



/**

 * snd_pcm_rate_mask_intersect - computes the intersection between two rate masks

 * @rates_a: The first rate mask

 * @rates_b: The second rate mask

 *

 * This function computes the rates that are supported by both rate masks passed

 * to the function. It will take care of the special handling of

 * SNDRV_PCM_RATE_CONTINUOUS and SNDRV_PCM_RATE_KNOT.

 *

 * Return: A rate mask containing the rates that are supported by both rates_a

 * and rates_b.

 */

unsigned int snd_pcm_rate_mask_intersect(unsigned int rates_a,

	unsigned int rates_b)

{

	rates_a = snd_pcm_rate_mask_sanitize(rates_a);

	rates_b = snd_pcm_rate_mask_sanitize(rates_b);



	if (rates_a & SNDRV_PCM_RATE_CONTINUOUS)

		return rates_b;

	else if (rates_b & SNDRV_PCM_RATE_CONTINUOUS)

		return rates_a;

	else if (rates_a & SNDRV_PCM_RATE_KNOT)

		return rates_b;

	else if (rates_b & SNDRV_PCM_RATE_KNOT)

		return rates_a;

	return rates_a & rates_b;

}

EXPORT_SYMBOL_GPL(snd_pcm_rate_mask_intersect);