edid: add basic support for display descriptors

Expose an API to list display descriptors. Detailed timing
descriptors are not parsed.

Signed-off-by: Simon Ser <contact@emersion.fr>

di-edid-decode.c

@@ -4,6 +4,51 @@
 #include <libdisplay-info/edid.h>
 #include <libdisplay-info/info.h>
 
+static const char *
+display_desc_tag_name(enum di_edid_display_descriptor_tag tag)
+{
+	static char name[256];
+	switch (tag) {
+	case DI_EDID_DISPLAY_DESCRIPTOR_PRODUCT_SERIAL:
+		return "Display Product Serial Number";
+	case DI_EDID_DISPLAY_DESCRIPTOR_DATA_STRING:
+		return "Alphanumeric Data String";
+	case DI_EDID_DISPLAY_DESCRIPTOR_RANGE_LIMITS:
+		return "Display Range Limits";
+	case DI_EDID_DISPLAY_DESCRIPTOR_PRODUCT_NAME:
+		return "Display Product Name";
+	case DI_EDID_DISPLAY_DESCRIPTOR_COLOR_POINT:
+		return "Color Point Data";
+	case DI_EDID_DISPLAY_DESCRIPTOR_STD_TIMING_IDS:
+		return "Standard Timing Identifications";
+	case DI_EDID_DISPLAY_DESCRIPTOR_DCM_DATA:
+		return "Display Color Management Data";
+	case DI_EDID_DISPLAY_DESCRIPTOR_CVT_TIMING_CODES:
+		return "CVT 3 Byte Timing Codes";
+	case DI_EDID_DISPLAY_DESCRIPTOR_ESTABLISHED_TIMINGS_III:
+		return "Established timings III";
+	case DI_EDID_DISPLAY_DESCRIPTOR_DUMMY:
+		return "Dummy Descriptor";
+	default:
+		snprintf(name, sizeof(name), "%s Display Descriptor (0x%02hhx)",
+			 tag <= 0x0F ? "Manufacturer-Specified" : "Unknown",
+			 tag);
+		return name;
+	}
+}
+
+static void
+print_display_desc(const struct di_edid_display_descriptor *desc)
+{
+	enum di_edid_display_descriptor_tag tag;
+	const char *tag_name;
+
+	tag = di_edid_display_descriptor_get_tag(desc);
+	tag_name = display_desc_tag_name(tag);
+
+	printf("    %s:\n", tag_name);
+}
+
 static const char *
 ext_tag_name(enum di_edid_ext_tag tag)
 {
@@ -51,6 +96,7 @@ main(void)
 	const struct di_edid *edid;
 	struct di_info *info;
 	const struct di_edid_vendor_product *vendor_product;
+	const struct di_edid_display_descriptor *const *display_descs;
 	const struct di_edid_ext *const *exts;
 	size_t i;
 
@@ -87,6 +133,12 @@ main(void)
 		       vendor_product->manufacture_year);
 	}
 
+	printf("  Detailed Timing Descriptors:\n");
+	display_descs = di_edid_get_display_descriptors(edid);
+	for (i = 0; display_descs[i] != NULL; i++) {
+		print_display_desc(display_descs[i]);
+	}
+
 	exts = di_edid_get_extensions(edid);
 
 	for (i = 0; exts[i] != NULL; i++);

edid.c

@@ -9,6 +9,10 @@
  * The size of an EDID block, defined in section 2.2.
  */
 #define EDID_BLOCK_SIZE 128
+/**
+ * The size of an EDID byte descriptor, defined in section 3.10.
+ */
+#define EDID_BYTE_DESCRIPTOR_SIZE 18
 
 /**
  * Fixed EDID header, defined in section 3.1.
@@ -76,6 +80,68 @@ parse_vendor_product(const uint8_t data[static EDID_BLOCK_SIZE],
 	}
 }
 
+static bool
+parse_byte_descriptor(struct di_edid *edid,
+		      const uint8_t data[static EDID_BYTE_DESCRIPTOR_SIZE])
+{
+	struct di_edid_display_descriptor *desc;
+	uint8_t tag;
+
+	if (data[0] || data[1]) {
+		if (edid->display_descriptors_len > 0) {
+			/* A detailed timing descriptor is not allowed after a
+			 * display descriptor per note 3 of table 3.20. */
+			errno = EINVAL;
+			return false;
+		}
+
+		/* TODO: parse detailed timing descriptor */
+		return true;
+	}
+
+	/* TODO: check we got at least one detailed timing descriptor, per note
+	 * 4 of table 3.20. */
+
+	desc = calloc(1, sizeof(*desc));
+	if (!desc) {
+		return false;
+	}
+
+	tag = data[3];
+	switch (tag) {
+	case DI_EDID_DISPLAY_DESCRIPTOR_PRODUCT_SERIAL:
+	case DI_EDID_DISPLAY_DESCRIPTOR_DATA_STRING:
+	case DI_EDID_DISPLAY_DESCRIPTOR_RANGE_LIMITS:
+	case DI_EDID_DISPLAY_DESCRIPTOR_PRODUCT_NAME:
+	case DI_EDID_DISPLAY_DESCRIPTOR_COLOR_POINT:
+	case DI_EDID_DISPLAY_DESCRIPTOR_STD_TIMING_IDS:
+	case DI_EDID_DISPLAY_DESCRIPTOR_DCM_DATA:
+	case DI_EDID_DISPLAY_DESCRIPTOR_CVT_TIMING_CODES:
+	case DI_EDID_DISPLAY_DESCRIPTOR_ESTABLISHED_TIMINGS_III:
+	case DI_EDID_DISPLAY_DESCRIPTOR_DUMMY:
+		break; /* Ignore */
+	default:
+		free(desc);
+		if (tag <= 0x0F) {
+			/* Manufacturer-specific */
+			errno = ENOTSUP;
+		} else {
+			/* Reserved */
+			if (edid->revision > 4) {
+				errno = ENOTSUP;
+			} else {
+				errno = EINVAL;
+			}
+		}
+		return false;
+	}
+
+	desc->tag = tag;
+	edid->display_descriptors[edid->display_descriptors_len++] = desc;
+
+	return true;
+}
+
 static bool
 parse_ext(struct di_edid *edid, const uint8_t data[static EDID_BLOCK_SIZE])
 {
@@ -120,7 +186,7 @@ di_edid_parse(const void *data, size_t size)
 	struct di_edid *edid;
 	int version, revision;
 	size_t exts_len, i;
-	const uint8_t *ext_data;
+	const uint8_t *byte_desc_data, *ext_data;
 
 	if (size < EDID_BLOCK_SIZE ||
 	    size > EDID_MAX_BLOCK_COUNT * EDID_BLOCK_SIZE ||
@@ -163,6 +229,16 @@ di_edid_parse(const void *data, size_t size)
 
 	parse_vendor_product(data, &edid->vendor_product);
 
+	for (i = 0; i < EDID_BYTE_DESCRIPTOR_COUNT; i++) {
+		byte_desc_data = (const uint8_t *) data
+			       + 0x36 + i * EDID_BYTE_DESCRIPTOR_SIZE;
+		if (!parse_byte_descriptor(edid, byte_desc_data)
+		    && errno != ENOTSUP) {
+			di_edid_destroy(edid);
+			return NULL;
+		}
+	}
+
 	for (i = 0; i < exts_len; i++) {
 		ext_data = (const uint8_t *) data + (i + 1) * EDID_BLOCK_SIZE;
 		if (!parse_ext(edid, ext_data) && errno != ENOTSUP) {
@@ -179,6 +255,10 @@ di_edid_destroy(struct di_edid *edid)
 {
 	size_t i;
 
+	for (i = 0; i < edid->display_descriptors_len; i++) {
+		free(edid->display_descriptors[i]);
+	}
+
 	for (i = 0; edid->exts[i] != NULL; i++) {
 		free(edid->exts[i]);
 	}
@@ -204,6 +284,18 @@ di_edid_get_vendor_product(const struct di_edid *edid)
 	return &edid->vendor_product;
 }
 
+const struct di_edid_display_descriptor *const *
+di_edid_get_display_descriptors(const struct di_edid *edid)
+{
+	return (const struct di_edid_display_descriptor *const *) &edid->display_descriptors;
+}
+
+enum di_edid_display_descriptor_tag
+di_edid_display_descriptor_get_tag(const struct di_edid_display_descriptor *desc)
+{
+	return desc->tag;
+}
+
 const struct di_edid_ext *const *
 di_edid_get_extensions(const struct di_edid *edid)
 {

include/edid.h

@@ -14,15 +14,26 @@
  * section 2.2.1.
  */
 #define EDID_MAX_BLOCK_COUNT 256
+/**
+ * The number of EDID byte descriptors, defined in section 3.10.
+ */
+#define EDID_BYTE_DESCRIPTOR_COUNT 4
 
 struct di_edid {
 	struct di_edid_vendor_product vendor_product;
 	int version, revision;
+	/* NULL-terminated */
+	struct di_edid_display_descriptor *display_descriptors[EDID_BYTE_DESCRIPTOR_COUNT + 1];
+	size_t display_descriptors_len;
 	/* NULL-terminated, doesn't include the base block */
 	struct di_edid_ext *exts[EDID_MAX_BLOCK_COUNT];
 	size_t exts_len;
 };
 
+struct di_edid_display_descriptor {
+	enum di_edid_display_descriptor_tag tag;
+};
+
 struct di_edid_ext {
 	enum di_edid_ext_tag tag;
 };

include/libdisplay-info/edid.h

@@ -46,6 +46,51 @@ struct di_edid_vendor_product {
 const struct di_edid_vendor_product *
 di_edid_get_vendor_product(const struct di_edid *edid);
 
+/**
+ * EDID display descriptor tag, defined in section 3.10.3.
+ */
+enum di_edid_display_descriptor_tag {
+	/* Display Product Serial Number */
+	DI_EDID_DISPLAY_DESCRIPTOR_PRODUCT_SERIAL = 0xFF,
+	/* Alphanumeric Data String (ASCII) */
+	DI_EDID_DISPLAY_DESCRIPTOR_DATA_STRING = 0xFE,
+	/* Display Range Limits */
+	DI_EDID_DISPLAY_DESCRIPTOR_RANGE_LIMITS = 0xFD,
+	/* Display Product Name */
+	DI_EDID_DISPLAY_DESCRIPTOR_PRODUCT_NAME = 0xFC,
+	/* Color Point Data */
+	DI_EDID_DISPLAY_DESCRIPTOR_COLOR_POINT = 0xFB,
+	/* Standard Timing Identifications */
+	DI_EDID_DISPLAY_DESCRIPTOR_STD_TIMING_IDS = 0xFA,
+	/* Display Color Management (DCM) Data */
+	DI_EDID_DISPLAY_DESCRIPTOR_DCM_DATA = 0xF9,
+	/* CVT 3 Byte Timing Codes */
+	DI_EDID_DISPLAY_DESCRIPTOR_CVT_TIMING_CODES = 0xF8,
+	/* Established Timings III */
+	DI_EDID_DISPLAY_DESCRIPTOR_ESTABLISHED_TIMINGS_III = 0xF7,
+	/* Dummy Descriptor */
+	DI_EDID_DISPLAY_DESCRIPTOR_DUMMY = 0x10,
+};
+
+/**
+ * Get a list of EDID display descriptors.
+ *
+ * The returned array is NULL-terminated.
+ */
+const struct di_edid_display_descriptor *const *
+di_edid_get_display_descriptors(const struct di_edid *edid);
+
+/**
+ * EDID display descriptor.
+ */
+struct di_edid_display_descriptor;
+
+/**
+ * Get the tag of an EDID display descriptor.
+ */
+enum di_edid_display_descriptor_tag
+di_edid_display_descriptor_get_tag(const struct di_edid_display_descriptor *desc);
+
 /**
  * Get a list of EDID extensions.
  *

test/data/dell-2408wfp-dp.diff

@@ -1,6 +1,6 @@
 --- ref
 +++ di
-@@ -5,39 +5,4 @@
+@@ -5,39 +5,8 @@
      Model: 41003
      Serial Number: 842091859
      Made in: week 47 of 2008
@@ -31,12 +31,14 @@
 -    DMT 0x23:  1280x1024   60.019740 Hz   5:4     63.981 kHz    108.000000 MHz
 -    DMT 0x33:  1600x1200   60.000000 Hz   4:3     75.000 kHz    162.000000 MHz
 -    DMT 0x15:  1152x864    75.000000 Hz   4:3     67.500 kHz    108.000000 MHz
--  Detailed Timing Descriptors:
+   Detailed Timing Descriptors:
 -    DTD 1:  1920x1200   59.950171 Hz   8:5     74.038 kHz    154.000000 MHz (519 mm x 320 mm)
 -                 Hfront   48 Hsync  32 Hback   80 Hpol P
 -                 Vfront    3 Vsync   6 Vback   26 Vpol N
 -    Display Product Serial Number: 'G283H8BI21MS'
 -    Display Product Name: 'DELL 2408WFP'
--    Display Range Limits:
++    Display Product Serial Number:
++    Display Product Name:
+     Display Range Limits:
 -      Monitor ranges (Bare Limits): 56-76 Hz V, 30-83 kHz H, max dotclock 170 MHz
  Checksum: 0x92

test/data/hp-5dq99aa-hdmi.diff

@@ -1,6 +1,6 @@
 --- ref
 +++ di
-@@ -5,103 +5,10 @@
+@@ -5,103 +5,14 @@
      Model: 13847
      Serial Number: 16843009
      Made in: week 12 of 2019
@@ -30,14 +30,16 @@
 -    DMT 0x2f:  1440x900    59.887445 Hz  16:10    55.935 kHz    106.500000 MHz
 -    DMT 0x33:  1600x1200   60.000000 Hz   4:3     75.000 kHz    162.000000 MHz
 -    DMT 0x23:  1280x1024   60.019740 Hz   5:4     63.981 kHz    108.000000 MHz
--  Detailed Timing Descriptors:
+   Detailed Timing Descriptors:
 -    DTD 1:  2560x1440   59.950550 Hz  16:9     88.787 kHz    241.500000 MHz (597 mm x 339 mm)
 -                 Hfront   48 Hsync  32 Hback   80 Hpol P
 -                 Vfront    3 Vsync   5 Vback   33 Vpol N
--    Display Range Limits:
+     Display Range Limits:
 -      Monitor ranges (GTF): 46-75 Hz V, 30-112 kHz H, max dotclock 310 MHz
 -    Display Product Name: 'HP 27 QD'
 -    Display Product Serial Number: 'CN49120J6N'
++    Display Product Name:
++    Display Product Serial Number:
    Extension blocks: 1
  Checksum: 0x20