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

[Takashi Iwai]

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.

I suppose this patchset will go through ASoC tree?  Then take my ack:

    Reviewed-by: Takashi Iwai <tiwai at suse.de>


thanks,

Takashi