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From:   Guillaume Ranquet <granquet@baylibre.com>
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Date:   Fri, 25 Feb 2022 02:35:31 -0800
Message-ID: <CABnWg9t0nW8NRkiLHvWRoavfUbOKL5wG00dbuY8qZW=WeTHxMw@mail.gmail.com>
Subject: Re: [PATCH v8 03/19] drm/edid: Add cea_sad helpers for freq/length
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>, airlied@linux.ie,
        chunfeng.yun@mediatek.com, chunkuang.hu@kernel.org,
        ck.hu@mediatek.com, daniel@ffwll.ch, deller@gmx.de,
        jitao.shi@mediatek.com, kishon@ti.com,
        maarten.lankhorst@linux.intel.com, matthias.bgg@gmail.com,
        mripard@kernel.org, p.zabel@pengutronix.de, robh+dt@kernel.org,
        tzimmermann@suse.de, vkoul@kernel.org
Cc:     dri-devel@lists.freedesktop.org,
        linux-mediatek@lists.infradead.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-phy@lists.infradead.org, linux-fbdev@vger.kernel.org,
        Markus Schneider-Pargmann <msp@baylibre.com>
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Quoting AngeloGioacchino Del Regno (2022-02-21 15:30:04)
> Il 18/02/22 15:54, Guillaume Ranquet ha scritto:
> > From: Markus Schneider-Pargmann <msp@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.
> >
> > Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> > Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
> > ---
> >   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 12893e7be89bb..500279a82167a 100644
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -4747,6 +4747,80 @@ 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 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);
> > +
> > +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 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 18f6c700f6d02..a30452b313979 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_* */
>
> Hello Guillaume,
>
> since you're adding comments to all the rest of the struct members,
> I think that a small effort to instead convert this to kerneldoc is
> totally worth it.
> Can you please do that?
>
> Thanks,
> Angelo
>
Hello Angelo,

Sure, that's a good suggestion.

Thx,
Guillaume.
> >       u8 channels; /* max number of channels - 1 */
> > -     u8 freq;
> > +     u8 freq; /* See CEA_SAD_FREQ_* */
> >       u8 byte2; /* meaning depends on format */
> >   };
> >
> > +#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;
> > @@ -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);
> >
>
>