On Tue, Mar 22, 2022 at 11:40:48PM +0200, Jani Nikula wrote:
> Convert drm_find_cea_extension() to a predicate function to check if the
> EDID has a CEA extension or a DisplayID CTA data block. This is mainly
> to avoid adding new users that only find the first CEA extension.
>
> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_edid.c | 17 ++++++++---------
> 1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index dfaa21f00941..84314b65b75b 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -3422,30 +3422,29 @@ const u8 *drm_find_edid_extension(const struct edid *edid,
> return edid_ext;
> }
>
> -static const u8 *drm_find_cea_extension(const struct edid *edid)
> +/* Return true if the EDID has a CEA extension or a DisplayID CTA data block */
> +static bool drm_edid_has_cea_extension(const struct edid *edid)
> {
> const struct displayid_block *block;
> struct displayid_iter iter;
> - const u8 *cea;
> int ext_index = 0;
> + bool found = false;
>
> /* Look for a top level CEA extension block */
> - /* FIXME: make callers iterate through multiple CEA ext blocks? */
> - cea = drm_find_edid_extension(edid, CEA_EXT, &ext_index);
> - if (cea)
> - return cea;
> + if (drm_find_edid_extension(edid, CEA_EXT, &ext_index))
> + return true;
>
> /* CEA blocks can also be found embedded in a DisplayID block */
> displayid_iter_edid_begin(edid, &iter);
> displayid_iter_for_each(block, &iter) {
> if (block->tag == DATA_BLOCK_CTA) {
> - cea = (const u8 *)block;
> + found = true;
> break;
> }
> }
> displayid_iter_end(&iter);
>
> - return cea;
> + return found;
> }
>
> static __always_inline const struct drm_display_mode *cea_mode_for_vic(u8 vic)
> @@ -3715,7 +3714,7 @@ add_alternate_cea_modes(struct drm_connector *connector, struct edid *edid)
> int modes = 0;
>
> /* Don't add CEA modes if the CEA extension block is missing */
> - if (!drm_find_cea_extension(edid))
> + if (!drm_edid_has_cea_extension(edid))
I'm thinking we could just do
if (modes)
modes += add_alternate_cea_modes(...);
at the end of add_cea_modes().
Or perhaps
if (found)
modes += add_alternate_cea_modes(...);
if we think that adding the alternate modes would be apporpriate
even when add_cea_modes() didn't add anything. Not sure.
Yes, that would still introduce a sligth change in behaviour
in case we have a CEA ext block/DisplayID CTA block without
any of the video/hdmi/y420vdb blocks, but that edge case
doesn't feel like a deal-breaker to me.
--
Ville Syrjälä
Intel
