[PATCH v2] drm: Don't block HDR_OUTPUT_METADATA on unknown EOTF

[Harry Wentland]

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 at amd.com>
Cc: ppaalanen at gmail.com
Cc: sebastian.wick at redhat.com
Cc: vprosyak at amd.com
Cc: Uma Shankar <uma.shankar at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Acked-by: Pekka Paalanen <pekka.paalanen at 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)
-- 
2.36.1