Hi Nicolas,
On Thu, Jun 18, 2026 at 08:54:23PM +0200, Nicolas Frattaroli wrote:
> As per the comment in sink_supports_format_bpc(), CTA-861-F defines that
> only bits-per-channel values of 8, 10, 12 and 16 are allowed for HDMI.
> Allowing more than this has surprising consequences for the atomic check
> phase. The HDMI state helpers may accidentally conclude that a sink
> supports 11bpc if a caller asks for it.
>
> Fix this by exiting early if the bpc value doesn't match one of those
> given in the standard.
>
> Fixes: 26ff1c38fc29 ("drm/connector: hdmi: Compute bpc and format
> automatically")
> Signed-off-by: Nicolas Frattaroli <[email protected]>
> ---
> drivers/gpu/drm/display/drm_hdmi_state_helper.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> index ce17eeefc2da..0bf6102244f7 100644
> --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> @@ -420,6 +420,16 @@ sink_supports_format_bpc(const struct drm_connector
> *connector,
> return false;
> }
>
> + switch (bpc) {
> + case 8:
> + case 10:
> + case 12:
> + case 16:
> + break;
> + default:
> + return false;
> + }
> +Sorry for not noticing in your first version, but I'd move this before the VIC 1 check, and would add a comment to refer to the spec (possibly by splitting the comment already there for the VIC 1 check). We should also log debug message on failure like we do for every other rejection path. Maxime
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