Re: [PATCH v15 03/11] drm/edid: Add cea_sad helpers for freq/length

[Jani Nikula]

On Wed, 27 Jul 2022, Bo-Chen Chen <rex-bc.chen@xxxxxxxxxxxx> wrote:
> From: Guillaume Ranquet <granquet@xxxxxxxxxxxx>
>
> 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.

I think we should stop adding a plethora of functions that deal with
sads like this.

There should probably be *one* struct that contains all the details you
and everyone need extracted. There should be *one* function that fills
in all the details. The struct should be placed in
connector->display_info, and the function should be called *once* from
update_display_info().

Ideally, the function shouldn't even be exposed from drm_edid.c, but if
you still need to deal with situations where you don't call connector
update, maybe it needs to be exposed.

BR,
Jani.


>
> Signed-off-by: Markus Schneider-Pargmann <msp@xxxxxxxxxxxx>
> Signed-off-by: Guillaume Ranquet <granquet@xxxxxxxxxxxx>
> Signed-off-by: Bo-Chen Chen <rex-bc.chen@xxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/drm_edid.c | 63 ++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_edid.h     | 14 +++++++++
>  2 files changed, 77 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index bc43e1b32092..2a6f92da5ff3 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -4916,6 +4916,69 @@ int drm_edid_to_speaker_allocation(const 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(const struct cea_sad *sad)
> +{
> +	switch (sad->freq) {
> +	case DRM_CEA_SAD_FREQ_32KHZ:
> +		return 32000;
> +	case DRM_CEA_SAD_FREQ_44KHZ:
> +		return 44100;
> +	case DRM_CEA_SAD_FREQ_48KHZ:
> +		return 48000;
> +	case DRM_CEA_SAD_FREQ_88KHZ:
> +		return 88200;
> +	case DRM_CEA_SAD_FREQ_96KHZ:
> +		return 96000;
> +	case DRM_CEA_SAD_FREQ_176KHZ:
> +		return 176400;
> +	case DRM_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.
> + *
> + * Return: Word length in bits or a negative errno if parsing failed.
> + */
> +int drm_cea_sad_get_uncompressed_word_length(const struct cea_sad *sad)
> +{
> +	if (sad->format != HDMI_AUDIO_CODING_TYPE_PCM) {
> +		DRM_WARN("Unable to get the uncompressed word length for format: %u\n",
> +			 sad->format);
> +		return -EINVAL;
> +	}
> +
> +	switch (sad->byte2) {
> +	case DRM_CEA_SAD_UNCOMPRESSED_WORD_16BIT:
> +		return 16;
> +	case DRM_CEA_SAD_UNCOMPRESSED_WORD_20BIT:
> +		return 20;
> +	case DRM_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 c2c43a4af681..779b710aed40 100644
> --- a/include/drm/drm_edid.h
> +++ b/include/drm/drm_edid.h
> @@ -373,6 +373,18 @@ struct cea_sad {
>  	u8 byte2;
>  };
>  
> +#define DRM_CEA_SAD_FREQ_32KHZ  BIT(0)
> +#define DRM_CEA_SAD_FREQ_44KHZ  BIT(1)
> +#define DRM_CEA_SAD_FREQ_48KHZ  BIT(2)
> +#define DRM_CEA_SAD_FREQ_88KHZ  BIT(3)
> +#define DRM_CEA_SAD_FREQ_96KHZ  BIT(4)
> +#define DRM_CEA_SAD_FREQ_176KHZ BIT(5)
> +#define DRM_CEA_SAD_FREQ_192KHZ BIT(6)
> +
> +#define DRM_CEA_SAD_UNCOMPRESSED_WORD_16BIT BIT(0)
> +#define DRM_CEA_SAD_UNCOMPRESSED_WORD_20BIT BIT(1)
> +#define DRM_CEA_SAD_UNCOMPRESSED_WORD_24BIT BIT(2)
> +
>  struct drm_encoder;
>  struct drm_connector;
>  struct drm_connector_state;
> @@ -380,6 +392,8 @@ struct drm_display_mode;
>  
>  int drm_edid_to_sad(const struct edid *edid, struct cea_sad **sads);
>  int drm_edid_to_speaker_allocation(const struct edid *edid, u8 **sadb);
> +int drm_cea_sad_get_sample_rate(const struct cea_sad *sad);
> +int drm_cea_sad_get_uncompressed_word_length(const struct cea_sad *sad);
>  int drm_av_sync_delay(struct drm_connector *connector,
>  		      const struct drm_display_mode *mode);

-- 
Jani Nikula, Intel Open Source Graphics Center