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    SubjectRe: [PATCH v15 03/11] drm/edid: Add cea_sad helpers for freq/length
    Date
    On Wed, 27 Jul 2022, Bo-Chen Chen <rex-bc.chen@mediatek.com> wrote:
    > From: Guillaume Ranquet <granquet@baylibre.com>
    >
    > 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@baylibre.com>
    > Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
    > Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
    > ---
    > 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

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