Re: [PATCH v1 3/6] drm/edid: Add cea_sad helpers for freq/length

[Sam Ravnborg <sam@ravnborg.org>]

Hi Markus,

On Mon, Sep 06, 2021 at 09:35:26PM +0200, Markus Schneider-Pargmann wrote:
> This patch adds two helper functions that extract the frequency and word
> length from a struct cea_sad.
> 
> For these helper functions new defines are added that help translate the
> 'freq' and 'byte2' fields into real numbers.
> 
> Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 57 ++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_edid.h     | 18 ++++++++++--
>  2 files changed, 73 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 81d5f2524246..2389d34ce10e 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -4666,6 +4666,63 @@ int drm_edid_to_speaker_allocation(struct edid *edid, u8 **sadb)
>  }
>  EXPORT_SYMBOL(drm_edid_to_speaker_allocation);
>  
> +/**
> + * drm_cea_sad_get_sample_rate - Extract the sample rate from cea_sad
> + * @sad: Pointer to the cea_sad struct
> + *
> + * Extracts the cea_sad frequency field and returns the sample rate in Hz.
> + *
> + * Return: Sample rate in Hz or a negative errno if parsing failed.
> + */
> +int drm_cea_sad_get_sample_rate(struct cea_sad *sad)

It would be nice to use const struct cea_sad *sad here.

> +{
> +	switch (sad->freq) {
> +	case CEA_SAD_FREQ_32KHZ:
> +		return 32000;
> +	case CEA_SAD_FREQ_44KHZ:
> +		return 44100;
> +	case CEA_SAD_FREQ_48KHZ:
> +		return 48000;
> +	case CEA_SAD_FREQ_88KHZ:
> +		return 88200;
> +	case CEA_SAD_FREQ_96KHZ:
> +		return 96000;
> +	case CEA_SAD_FREQ_176KHZ:
> +		return 176400;
> +	case CEA_SAD_FREQ_192KHZ:
> +		return 192000;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +EXPORT_SYMBOL(drm_cea_sad_get_sample_rate);
> +
> +/**
> + * drm_cea_sad_get_uncompressed_word_length - Extract word length
> + * @sad: Pointer to the cea_sad struct
> + *
> + * Extracts the cea_sad byte2 field and returns the word length for an
> + * uncompressed stream.
> + *
> + * Note: This function may only be called for uncompressed audio.
Can you check or this and WARN (or drm_WARN) if this is not the case?

> + *
> + * Return: Word length in bits or a negative errno if parsing failed.
> + */
> +int drm_cea_sad_get_uncompressed_word_length(struct cea_sad *sad)
Again, consider to use const.

	Sam

> +{
> +	switch (sad->byte2) {
> +	case CEA_SAD_UNCOMPRESSED_WORD_16BIT:
> +		return 16;
> +	case CEA_SAD_UNCOMPRESSED_WORD_20BIT:
> +		return 20;
> +	case CEA_SAD_UNCOMPRESSED_WORD_24BIT:
> +		return 24;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +EXPORT_SYMBOL(drm_cea_sad_get_uncompressed_word_length);
> +
>  /**
>   * drm_av_sync_delay - compute the HDMI/DP sink audio-video sync delay
>   * @connector: connector associated with the HDMI/DP sink
> diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
> index 759328a5eeb2..bed091a749ef 100644
> --- a/include/drm/drm_edid.h
> +++ b/include/drm/drm_edid.h
> @@ -361,12 +361,24 @@ struct edid {
>  
>  /* Short Audio Descriptor */
>  struct cea_sad {
> -	u8 format;
> +	u8 format; /* See HDMI_AUDIO_CODING_TYPE_* */
>  	u8 channels; /* max number of channels - 1 */
> -	u8 freq;
> +	u8 freq; /* See CEA_SAD_FREQ_* */
>  	u8 byte2; /* meaning depends on format */
>  };
>  
> +#define CEA_SAD_FREQ_32KHZ  BIT(0)
> +#define CEA_SAD_FREQ_44KHZ  BIT(1)
> +#define CEA_SAD_FREQ_48KHZ  BIT(2)
> +#define CEA_SAD_FREQ_88KHZ  BIT(3)
> +#define CEA_SAD_FREQ_96KHZ  BIT(4)
> +#define CEA_SAD_FREQ_176KHZ BIT(5)
> +#define CEA_SAD_FREQ_192KHZ BIT(6)
> +
> +#define CEA_SAD_UNCOMPRESSED_WORD_16BIT BIT(0)
> +#define CEA_SAD_UNCOMPRESSED_WORD_20BIT BIT(1)
> +#define CEA_SAD_UNCOMPRESSED_WORD_24BIT BIT(2)
> +
>  struct drm_encoder;
>  struct drm_connector;
>  struct drm_connector_state;
> @@ -374,6 +386,8 @@ struct drm_display_mode;
>  
>  int drm_edid_to_sad(struct edid *edid, struct cea_sad **sads);
>  int drm_edid_to_speaker_allocation(struct edid *edid, u8 **sadb);
> +int drm_cea_sad_get_sample_rate(struct cea_sad *sad);
> +int drm_cea_sad_get_uncompressed_word_length(struct cea_sad *sad);
>  int drm_av_sync_delay(struct drm_connector *connector,
>  		      const struct drm_display_mode *mode);
>  
> -- 
> 2.33.0

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