Re: [PATCH v2 3/6] drm/edid: Add cea_sad helpers for freq/length

[Markus Schneider-Pargmann <msp@baylibre.com>]

Hi Jani,

On Tue, Sep 21, 2021 at 12:49:31PM +0300, Jani Nikula wrote:
> On Mon, 20 Sep 2021, Markus Schneider-Pargmann <msp@baylibre.com> 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>
> > ---
> >
> > Notes:
> >     Changes v1 -> v2:
> >     - Use const struct pointers.
> >     - Add a check whether the format is actually uncompressed or not.
> >
> >  drivers/gpu/drm/drm_edid.c | 74 ++++++++++++++++++++++++++++++++++++++
> >  include/drm/drm_edid.h     | 18 ++++++++--
> >  2 files changed, 90 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> > index 6325877c5fd6..28df422fbc03 100644
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -4666,6 +4666,80 @@ 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(const struct cea_sad *sad)
> > +{
> > +	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);
> > +
> > +static bool drm_cea_sad_is_uncompressed(const struct cea_sad *sad)
> > +{
> > +	switch (sad->format) {
> > +	case HDMI_AUDIO_CODING_TYPE_STREAM:
> > +	case HDMI_AUDIO_CODING_TYPE_PCM:
> > +		return true;
> > +	default:
> > +		return false;
> > +	}
> > +}
> > +
> > +/**
> > + * 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 (!drm_cea_sad_is_uncompressed(sad)) {
> > +		DRM_WARN("Unable to get the uncompressed word length for a compressed format: %u\n",
> > +			 sad->format);
> > +		return -EINVAL;
> > +	}
> > +
> > +	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 deccfd39e6db..7b7d71a7154d 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)
> 
> I suggest adding DRM_ prefixes here.

Thanks, will do that.

Best,
Markus

> 
> BR,
> Jani.
> 
> > +
> >  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(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