[PATCH 1/3] drm/edid: parse multiple CEA extension block

[Ville Syrjälä]

On Tue, Feb 22, 2022 at 02:38:17PM +0800, Lee Shawn C wrote:
> Try to find and parse more CEA ext blocks if edid->extensions
> is greater than one.
> 
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> Cc: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> Signed-off-by: Lee Shawn C <shawn.c.lee at intel.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 75 +++++++++++++++++++++++---------------
>  1 file changed, 45 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 12893e7be89b..3d5dbbeca7f9 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -4313,43 +4313,58 @@ add_cea_modes(struct drm_connector *connector, struct edid *edid)
>  	const u8 *cea = drm_find_cea_extension(edid);
>  	const u8 *db, *hdmi = NULL, *video = NULL;
>  	u8 dbl, hdmi_len, video_len = 0;
> -	int modes = 0;
> +	int modes = 0, j;
>  
> -	if (cea && cea_revision(cea) >= 3) {
> -		int i, start, end;
> +	if (!cea)
> +		return 0;
>  
> -		if (cea_db_offsets(cea, &start, &end))
> -			return 0;
> +	for (j = (cea - (u8 *)edid) / EDID_LENGTH; j <= edid->extensions;) {

That looks rather illegible. I think we want a
drm_find_cea_extension(const struct edid *edid, int *ext_index)
and then just loop until it stops giving us stuff.

There are also several other callers of drm_find_cea_extension().
Why don't they require the same treatment?

> +		if (cea && cea_revision(cea) >= 3) {
> +			int i, start, end;
>  
> -		for_each_cea_db(cea, i, start, end) {
> -			db = &cea[i];
> -			dbl = cea_db_payload_len(db);
> +			if (cea_db_offsets(cea, &start, &end))
> +				continue;
>  
> -			if (cea_db_tag(db) == VIDEO_BLOCK) {
> -				video = db + 1;
> -				video_len = dbl;
> -				modes += do_cea_modes(connector, video, dbl);
> -			} else if (cea_db_is_hdmi_vsdb(db)) {
> -				hdmi = db;
> -				hdmi_len = dbl;
> -			} else if (cea_db_is_y420vdb(db)) {
> -				const u8 *vdb420 = &db[2];
> -
> -				/* Add 4:2:0(only) modes present in EDID */
> -				modes += do_y420vdb_modes(connector,
> -							  vdb420,
> -							  dbl - 1);
> +			for_each_cea_db(cea, i, start, end) {
> +				db = &cea[i];
> +				dbl = cea_db_payload_len(db);
> +
> +				if (cea_db_tag(db) == VIDEO_BLOCK) {
> +					video = db + 1;
> +					video_len = dbl;
> +					modes += do_cea_modes(connector, video, dbl);
> +				} else if (cea_db_is_hdmi_vsdb(db)) {
> +					hdmi = db;
> +					hdmi_len = dbl;
> +				} else if (cea_db_is_y420vdb(db)) {
> +					const u8 *vdb420 = &db[2];
> +
> +					/* Add 4:2:0(only) modes present in EDID */
> +					modes += do_y420vdb_modes(connector,
> +								  vdb420,
> +								  dbl - 1);
> +				}
>  			}
>  		}
> -	}
>  
> -	/*
> -	 * We parse the HDMI VSDB after having added the cea modes as we will
> -	 * be patching their flags when the sink supports stereo 3D.
> -	 */
> -	if (hdmi)
> -		modes += do_hdmi_vsdb_modes(connector, hdmi, hdmi_len, video,
> -					    video_len);
> +		/*
> +		 * We parse the HDMI VSDB after having added the cea modes as we will
> +		 * be patching their flags when the sink supports stereo 3D.
> +		 */
> +		if (hdmi) {
> +			modes += do_hdmi_vsdb_modes(connector, hdmi, hdmi_len, video,
> +						    video_len);
> +			hdmi  = NULL;
> +			video = NULL;
> +			hdmi_len = 0;
> +			video_len = 0;
> +		}
> +
> +		/* move to next CEA extension block */
> +		cea = drm_find_edid_extension(edid, CEA_EXT, &j);
> +		if (!cea)
> +			break;
> +	}
>  
>  	return modes;
>  }
> -- 
> 2.17.1

-- 
Ville Syrjälä
Intel