Re: [PATCH v6 2/7] drm/edid: prepare for VESA vendor-specific data block extension

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 26 Nov 2025, Yaroslav Bolyukin <iam@lach.pw> wrote:
> Current VESA vendor-specific block parsing expects real block size to be
> the same as the defined struct size, use real offsets in conditionals
> instead to add struct fields in future commits.
>
> Signed-off-by: Yaroslav Bolyukin <iam@lach.pw>

I think this is something we want to backport, since MSO would break
with bigger vendor-specific blocks, and that leads to black screens on
MSO displays.

Cc: stable@vger.kernel.org
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

> ---
>  drivers/gpu/drm/drm_edid.c | 28 ++++++++++++----------------
>  1 file changed, 12 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 64f7a94dd9e4..a52fd6de9327 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -6544,7 +6544,7 @@ static void drm_parse_vesa_specific_block(struct drm_connector *connector,
>  	if (oui(vesa->oui[0], vesa->oui[1], vesa->oui[2]) != VESA_IEEE_OUI)
>  		return;
>  
> -	if (sizeof(*vesa) != sizeof(*block) + block->num_bytes) {
> +	if (block->num_bytes < 5) {
>  		drm_dbg_kms(connector->dev,
>  			    "[CONNECTOR:%d:%s] Unexpected VESA vendor block size\n",
>  			    connector->base.id, connector->name);
> @@ -6567,24 +6567,20 @@ static void drm_parse_vesa_specific_block(struct drm_connector *connector,
>  		break;
>  	}
>  
> -	if (!info->mso_stream_count) {
> -		info->mso_pixel_overlap = 0;
> -		return;
> -	}
> -
> -	info->mso_pixel_overlap = FIELD_GET(DISPLAYID_VESA_MSO_OVERLAP, vesa->mso);
> -	if (info->mso_pixel_overlap > 8) {
> +	if (info->mso_stream_count) {
> +		info->mso_pixel_overlap = FIELD_GET(DISPLAYID_VESA_MSO_OVERLAP, vesa->mso);
> +		if (info->mso_pixel_overlap > 8) {
> +			drm_dbg_kms(connector->dev,
> +				    "[CONNECTOR:%d:%s] Reserved MSO pixel overlap value %u\n",
> +				    connector->base.id, connector->name,
> +				    info->mso_pixel_overlap);
> +			info->mso_pixel_overlap = 8;
> +		}
>  		drm_dbg_kms(connector->dev,
> -			    "[CONNECTOR:%d:%s] Reserved MSO pixel overlap value %u\n",
> +			    "[CONNECTOR:%d:%s] MSO stream count %u, pixel overlap %u\n",
>  			    connector->base.id, connector->name,
> -			    info->mso_pixel_overlap);
> -		info->mso_pixel_overlap = 8;
> +			    info->mso_stream_count, info->mso_pixel_overlap);
>  	}
> -
> -	drm_dbg_kms(connector->dev,
> -		    "[CONNECTOR:%d:%s] MSO stream count %u, pixel overlap %u\n",
> -		    connector->base.id, connector->name,
> -		    info->mso_stream_count, info->mso_pixel_overlap);
>  }
>  
>  static void drm_update_vesa_specific_block(struct drm_connector *connector,

-- 
Jani Nikula, Intel