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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: Lars-Peter Clausen <lars@metafoo.de>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@linaro.org>
This commit is contained in:
Lars-Peter Clausen 2014-01-11 10:24:43 +01:00 committed by Mark Brown
parent bf103eb4af
commit e3a9269f87
2 changed files with 41 additions and 0 deletions
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2
include/sound/pcm.h
View File

@ -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)

39
sound/core/pcm_misc.c
View File

@ -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);