drm: Add HLG EOTF

ADD HLG EOTF to the list of EOTF transfer functions supported.
Hybrid Log-Gamma (HLG) is a high dynamic range (HDR) standard.
HLG defines a nonlinear transfer function in which the lower
half of the signal values use a gamma curve and the upper half
of the signal values use a logarithmic curve.

v2: Rebase

v3: Fixed a warning message

v4: Addressed Shashank's review comments

v5: Addressed Jonas Karlman's review comment and dropped the i915
tag from header.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1558015817-12025-8-git-send-email-uma.shankar@intel.com

drivers/gpu/drm/drm_edid.c

@@ -3854,7 +3854,8 @@ static uint8_t eotf_supported(const u8 *edid_ext)
 	return edid_ext[2] &
 		(BIT(HDMI_EOTF_TRADITIONAL_GAMMA_SDR) |
 		 BIT(HDMI_EOTF_TRADITIONAL_GAMMA_HDR) |
-		 BIT(HDMI_EOTF_SMPTE_ST2084));
+		 BIT(HDMI_EOTF_SMPTE_ST2084) |
+		 BIT(HDMI_EOTF_BT_2100_HLG));
 }
 
 static uint8_t hdr_metadata_type(const u8 *edid_ext)

include/linux/hdmi.h

@@ -162,6 +162,7 @@ enum hdmi_eotf {
 	HDMI_EOTF_TRADITIONAL_GAMMA_SDR,
 	HDMI_EOTF_TRADITIONAL_GAMMA_HDR,
 	HDMI_EOTF_SMPTE_ST2084,
+	HDMI_EOTF_BT_2100_HLG,
 };
 
 struct hdmi_avi_infoframe {