[alsa-devel] [PATCH 4/5] ALSA: Add helper function for intersecting two rate masks

[Lars-Peter Clausen]

On 01/10/2014 04:17 PM, Takashi Iwai wrote:
> At Fri, 10 Jan 2014 16:06:35 +0100,
> Lars-Peter Clausen wrote:
>>
>> 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 at metafoo.de>
>> ---
>>  include/sound/pcm.h   |  2 ++
>>  sound/core/pcm_misc.c | 39 +++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 41 insertions(+)
>>
>> diff --git a/include/sound/pcm.h b/include/sound/pcm.h
>> index 84b10f9..d017091 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)
>> diff --git a/sound/core/pcm_misc.c b/sound/core/pcm_misc.c
>> index 43f24cc..1552537 100644
>> --- a/sound/core/pcm_misc.c
>> +++ b/sound/core/pcm_misc.c
>> @@ -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(snd_pcm_rate_mask_intersect);
> 
> We can use EXPORT_SYMBOL_GPL() for new functions safely.

Ok, I'll change that.

> 
> I suppose this patchset will go through ASoC tree?  Then take my ack:
> 
>     Reviewed-by: Takashi Iwai <tiwai at suse.de>

Thanks.