[v6 03/13] drm: Parse Colorimetry data block from EDID

[Brian Starkey]

Hi Uma,

On Wed, Mar 20, 2019 at 04:18:16PM +0530, Uma Shankar wrote:
> CEA 861.3 spec adds colorimetry data block for HDMI.
> Parsing the block to get the colorimetry data from
> panel.
> 

While code which parses these parts (patches 2 and 3) out of EDID
could be useful - it doesn't seem to actually be used anywhere in the
kernel (sorry if I missed it), and I'm not sure it will/can be unless
we expose more properties.

The discussion last time leant towards a more useful/generic userspace
library for EDID parsing, so perhaps patches 2 and 3 should be
dropped.

Did you have an intended use for them in the kernel?

Thanks,
-Brian

> v2: Rebase
> 
> v3: No Change
> 
> v4: Addressed Shashank's review comments. Updated
> colorimetry field to 16 bit as DCI-P3 got added
> in CEA 861-G spec, as pointed out by Shashank.
> 
> v5: Fixed checkpatch warnings with --strict option.
> 
> Signed-off-by: Uma Shankar <uma.shankar at intel.com>
> Reviewed-by: Shashank Sharma <shashank.sharma at intel.com>
> ---
>  drivers/gpu/drm/drm_edid.c  | 25 +++++++++++++++++++++++++
>  include/drm/drm_connector.h |  3 +++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index fd8a621a..676569b 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -2840,6 +2840,7 @@ static int drm_cvt_modes(struct drm_connector *connector,
>  #define VIDEO_BLOCK     0x02
>  #define VENDOR_BLOCK    0x03
>  #define SPEAKER_BLOCK	0x04
> +#define COLORIMETRY_DATA_BLOCK		0x5
>  #define HDR_STATIC_METADATA_BLOCK	0x6
>  #define USE_EXTENDED_TAG 0x07
>  #define EXT_VIDEO_CAPABILITY_BLOCK 0x00
> @@ -3829,6 +3830,28 @@ static void fixup_detailed_cea_mode_clock(struct drm_display_mode *mode)
>  	mode->clock = clock;
>  }
>  
> +static bool cea_db_is_hdmi_colorimetry_data_block(const u8 *db)
> +{
> +	if (cea_db_tag(db) != USE_EXTENDED_TAG)
> +		return false;
> +
> +	if (db[1] != COLORIMETRY_DATA_BLOCK)
> +		return false;
> +
> +	return true;
> +}
> +
> +static void
> +drm_parse_colorimetry_data_block(struct drm_connector *connector, const u8 *db)
> +{
> +	struct drm_hdmi_info *info = &connector->display_info.hdmi;
> +	u16 len;
> +
> +	len = cea_db_payload_len_ext(db);
> +	/* As per CEA 861-G spec */
> +	info->colorimetry = ((db[3] & (0x1 << 7)) << 1) | db[2];
> +}
> +
>  static bool cea_db_is_hdmi_hdr_metadata_block(const u8 *db)
>  {
>  	if (cea_db_tag(db) != USE_EXTENDED_TAG)
> @@ -4498,6 +4521,8 @@ static void drm_parse_cea_ext(struct drm_connector *connector,
>  			drm_parse_vcdb(connector, db);
>  		if (cea_db_is_hdmi_hdr_metadata_block(db))
>  			drm_parse_hdr_metadata_block(connector, db);
> +		if (cea_db_is_hdmi_colorimetry_data_block(db))
> +			drm_parse_colorimetry_data_block(connector, db);
>  	}
>  }
>  
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 29388bd..94f926e 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -206,6 +206,9 @@ struct drm_hdmi_info {
>  
>  	/** @y420_dc_modes: bitmap of deep color support index */
>  	u8 y420_dc_modes;
> +
> +	/* @colorimetry: bitmap of supported colorimetry modes */
> +	u16 colorimetry;
>  };
>  
>  /**
> -- 
> 1.9.1
>