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>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 84b10f9a2832..d0170913374d 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -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)