info: add di_info_get_supported_signal_colorimetry()

Add a high-level function to get the supported additional signal
colorimetries. This is only an interesting sub-set of the CTA-861-H
defined colorimetries, for driving WCG and HDR displays.

Wayland compositors will be interested in this.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

include/info.h

@@ -14,6 +14,7 @@
 struct di_derived_info {
 	struct di_hdr_static_metadata hdr_static_metadata;
 	struct di_color_primaries color_primaries;
+	struct di_supported_signal_colorimetry supported_signal_colorimetry;
 };
 
 struct di_info {

include/libdisplay-info/info.h

@@ -194,4 +194,44 @@ struct di_color_primaries {
 const struct di_color_primaries *
 di_info_get_default_color_primaries(const struct di_info *info);
 
+/** Additional signal colorimetry encodings supported by the display */
+struct di_supported_signal_colorimetry {
+	/* Rec. ITU-R BT.2020 constant luminance YCbCr */
+	bool bt2020_cycc;
+	/* Rec. ITU-R BT.2020 non-constant luminance YCbCr */
+	bool bt2020_ycc;
+	/* Rec. ITU-R BT.2020 RGB */
+	bool bt2020_rgb;
+	/* SMPTE ST 2113 RGB: P3D65 and P3DCI */
+	bool st2113_rgb;
+	/* Rec. ITU-R BT.2100 ICtCp HDR (with PQ and/or HLG) */
+	bool ictcp;
+};
+
+/**
+ * Get signal colorimetry encodings supported by the display
+ *
+ * These signal colorimetry encodings are supported in addition to the
+ * display's default RGB colorimetry. When you wish to use one of the additional
+ * encodings, they need to be explicitly enabled in the video signal. How to
+ * do that is specific to the signalling used, e.g. HDMI.
+ *
+ * Signal colorimetry encoding provides the color space that the signal is
+ * encoded for. This includes primary and white point chromaticities, and the
+ * YCbCr-RGB conversion if necessary. Also the transfer function is implied
+ * unless explicitly set otherwise, e.g. with HDR static metadata.
+ * See ANSI/CTA-861-H for details.
+ *
+ * The signal color volume can be considerably larger than the physically
+ * displayable color volume.
+ *
+ * The returned pointer is owned by the struct di_info passed in. It remains
+ * valid only as long as the di_info exists, and must not be freed by the
+ * caller.
+ *
+ * This function does not return NULL.
+ */
+const struct di_supported_signal_colorimetry *
+di_info_get_supported_signal_colorimetry(const struct di_info *info);
+
 #endif

info.c

@@ -146,6 +146,29 @@ derive_edid_color_primaries(const struct di_edid *edid,
 	}
 }
 
+static void
+derive_edid_supported_signal_colorimetry(const struct di_edid *edid,
+					 struct di_supported_signal_colorimetry *ssc)
+{
+	const struct di_cta_data_block *block;
+	const struct di_cta_colorimetry_block *cm;
+
+	/* Defaults to all unsupported. */
+
+	block = di_edid_get_cta_data_block(edid, DI_CTA_DATA_BLOCK_COLORIMETRY);
+	if (!block)
+		return;
+
+	cm = di_cta_data_block_get_colorimetry(block);
+	assert(cm);
+
+	ssc->bt2020_cycc = cm->bt2020_cycc;
+	ssc->bt2020_ycc = cm->bt2020_ycc;
+	ssc->bt2020_rgb = cm->bt2020_rgb;
+	ssc->st2113_rgb = cm->st2113_rgb;
+	ssc->ictcp = cm->ictcp;
+}
+
 struct di_info *
 di_info_parse_edid(const void *data, size_t size)
 {
@@ -175,6 +198,7 @@ di_info_parse_edid(const void *data, size_t size)
 
 	derive_edid_hdr_static_metadata(info->edid, &info->derived.hdr_static_metadata);
 	derive_edid_color_primaries(info->edid, &info->derived.color_primaries);
+	derive_edid_supported_signal_colorimetry(info->edid, &info->derived.supported_signal_colorimetry);
 
 	return info;
 
@@ -344,3 +368,9 @@ di_info_get_default_color_primaries(const struct di_info *info)
 {
 	return &info->derived.color_primaries;
 }
+
+const struct di_supported_signal_colorimetry *
+di_info_get_supported_signal_colorimetry(const struct di_info *info)
+{
+	return &info->derived.supported_signal_colorimetry;
+}