The EDID of an HDR display defines EOTFs that are supported by the display and can be set in the HDR metadata infoframe. Userspace is expected to read the EDID and set an appropriate HDR_OUTPUT_METADATA.
In drm_parse_hdr_metadata_block the kernel reads the supported EOTFs from the EDID and stores them in the drm_connector->hdr_sink_metadata. While doing so it also filters the EOTFs to the EOTFs the kernel knows about. When an HDR_OUTPUT_METADATA is set it then checks to make sure the EOTF is a supported EOTF. In cases where the kernel doesn't know about a new EOTF this check will fail, even if the EDID advertises support.
Since it is expected that userspace reads the EDID to understand what the display supports it doesn't make sense for DRM to block an HDR_OUTPUT_METADATA if it contains an EOTF the kernel doesn't understand.
This comes with the added benefit of future-proofing metadata support. If the spec defines a new EOTF there is no need to update DRM and an compositor can immediately make use of it.
Fixes: https://gitlab.freedesktop.org/wayland/weston/-/issues/609
v2: Distinguish EOTFs defind in kernel and ones defined in EDID in the commit description (Pekka)
Signed-off-by: Harry Wentland harry.wentland@amd.com Cc: ppaalanen@gmail.com Cc: sebastian.wick@redhat.com Cc: vprosyak@amd.com Cc: Uma Shankar uma.shankar@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Acked-by: Pekka Paalanen pekka.paalanen@collabora.com --- drivers/gpu/drm/drm_edid.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index 12893e7be89b..223f96a72064 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -5691,10 +5691,8 @@ drm_hdmi_infoframe_set_hdr_metadata(struct hdmi_drm_infoframe *frame,
/* Sink EOTF is Bit map while infoframe is absolute values */ if (!is_eotf_supported(hdr_metadata->hdmi_metadata_type1.eotf, - connector->hdr_sink_metadata.hdmi_type1.eotf)) { - DRM_DEBUG_KMS("EOTF Not Supported\n"); - return -EINVAL; - } + connector->hdr_sink_metadata.hdmi_type1.eotf)) + DRM_DEBUG_KMS("Unknown EOTF %d\n", hdr_metadata->hdmi_metadata_type1.eotf);
err = hdmi_drm_infoframe_init(frame); if (err < 0)