[v2] drm/edid: check basic audio support on CEA extension block

[Jani Nikula]

On Wed, 23 Mar 2022, Lee Shawn C <shawn.c.lee at intel.com> wrote:
> From: Cooper Chiou <cooper.chiou at intel.com>
>
> Tag code stored in bit7:5 for CTA block byte[3] is not the same as
> CEA extension block definition. Only check CEA block has
> basic audio support.
>
> Cc: Jani Nikula <jani.nikula at intel.com>
> Cc: Shawn C Lee <shawn.c.lee at intel.com>
> Cc: intel-gfx <intel-gfx at lists.freedesktop.org>
> Signed-off-by: Cooper Chiou <cooper.chiou at intel.com>
> Signed-off-by: Lee Shawn C <shawn.c.lee at intel.com>

Fixes: e28ad544f462 ("drm/edid: parse CEA blocks embedded in DisplayID")
Cc: <stable at vger.kernel.org> # v4.15
Reviewed-by: Jani Nikula <jani.nikula at intel.com>

(commit e28ad544f462 was merged in v5.3, but it has Cc: stable for
v4.15.)

Also drm_edid_to_eld() and drm_parse_cea_ext() are affected by the same
issue. For the former, it doesn't really matter all that much, it just
ends up using the DisplayID data block version instead, but the latter
adds bogus color formats and should be fixed. Patch follows.

All of these are fixed in my recent series [1], but we'll want the
simple fixes for stable first.

BR,
Jani.

[1] https://patchwork.freedesktop.org/series/101659/

> ---
>  drivers/gpu/drm/drm_edid.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 561f53831e29..f07af6786cec 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -4859,7 +4859,8 @@ bool drm_detect_monitor_audio(struct edid *edid)
>  	if (!edid_ext)
>  		goto end;
>  
> -	has_audio = ((edid_ext[3] & EDID_BASIC_AUDIO) != 0);
> +	has_audio = (edid_ext[0] == CEA_EXT &&
> +		    (edid_ext[3] & EDID_BASIC_AUDIO) != 0);
>  
>  	if (has_audio) {
>  		DRM_DEBUG_KMS("Monitor has basic audio support\n");

-- 
Jani Nikula, Intel Open Source Graphics Center