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.

Bug: https://gitlab.freedesktop.org/wayland/weston/-/issues/609

v2: Distinguish EOTFs defind in kernel and ones defined
    in EDID in the commit description (Pekka)

v3: Rebase; drm_hdmi_infoframe_set_hdr_metadata moved
    to drm_hdmi_helper.c
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Cc: Pekka Paalanen <ppaalanen@gmail.com>
Cc: Sebastian Wick <sebastian.wick@redhat.com>
Cc: Vitaly.Prosyak@amd.com
Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Joshua Ashton <joshua@froggi.es>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
Cc: amd-gfx@lists.freedesktop.org
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-By: Joshua Ashton <joshua@froggi.es>
Link: https://patchwork.freedesktop.org/patch/msgid/20230113162428.33874-2-harry.wentland@amd.comSigned-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org