Add basic support for DisplayID in EDID extension blocks

Establish the new headers and structs, and just parse the
version/revision for now.

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

di-edid-decode.c

@@ -7,6 +7,7 @@
 
 #include <libdisplay-info/cta.h>
 #include <libdisplay-info/edid.h>
+#include <libdisplay-info/displayid.h>
 #include <libdisplay-info/info.h>
 
 static size_t num_detailed_timing_defs = 0;
@@ -418,6 +419,8 @@ ext_tag_name(enum di_edid_ext_tag tag)
 		return "Block Map Extension Block";
 	case DI_EDID_EXT_VENDOR:
 		return "Manufacturer-Specific Extension Block";
+	case DI_EDID_EXT_DISPLAYID:
+		return "DisplayID Extension Block";
 	}
 	abort();
 }
@@ -674,6 +677,13 @@ print_cta(const struct di_edid_cta *cta)
 	}
 }
 
+static void
+print_displayid(const struct di_displayid *displayid)
+{
+	printf("  Version: %d.%d\n", di_displayid_get_version(displayid),
+	       di_displayid_get_revision(displayid));
+}
+
 static void
 print_ext(const struct di_edid_ext *ext, size_t ext_index)
 {
@@ -687,6 +697,9 @@ print_ext(const struct di_edid_ext *ext, size_t ext_index)
 	case DI_EDID_EXT_CEA:
 		print_cta(di_edid_ext_get_cta(ext));
 		break;
+	case DI_EDID_EXT_DISPLAYID:
+		print_displayid(di_edid_ext_get_displayid(ext));
+		break;
 	default:
 		break; /* Ignore */
 	}

displayid.c

@@ -0,0 +1,35 @@
+#include <errno.h>
+
+#include "bits.h"
+#include "displayid.h"
+
+bool
+_di_displayid_parse(struct di_displayid *displayid, const uint8_t *data,
+		    size_t size, struct di_logger *logger)
+{
+	if (size < 5) {
+		errno = EINVAL;
+		return false;
+	}
+
+	displayid->version = get_bit_range(data[0x00], 7, 4);
+	displayid->revision = get_bit_range(data[0x00], 3, 0);
+	if (displayid->version == 0 || displayid->version > 1) {
+		errno = ENOTSUP;
+		return false;
+	}
+
+	return true;
+}
+
+int
+di_displayid_get_version(const struct di_displayid *displayid)
+{
+	return displayid->version;
+}
+
+int
+di_displayid_get_revision(const struct di_displayid *displayid)
+{
+	return displayid->revision;
+}

edid.c

@@ -764,6 +764,21 @@ parse_ext(struct di_edid *edid, const uint8_t data[static EDID_BLOCK_SIZE])
 	case DI_EDID_EXT_VENDOR:
 		/* Supported */
 		break;
+	case DI_EDID_EXT_DISPLAYID:
+		snprintf(section_name, sizeof(section_name),
+			 "Block %zu, DisplayID Extension Block",
+			 edid->exts_len + 1);
+		logger = (struct di_logger) {
+			.f = edid->logger->f,
+			.section = section_name,
+		};
+
+		if (!_di_displayid_parse(&ext->displayid, &data[1],
+					 EDID_BLOCK_SIZE - 2, &logger)) {
+			free(ext);
+			return false;
+		}
+		break;
 	default:
 		/* Unsupported */
 		free(ext);
@@ -1115,3 +1130,12 @@ di_edid_ext_get_cta(const struct di_edid_ext *ext)
 	}
 	return &ext->cta;
 }
+
+const struct di_displayid *
+di_edid_ext_get_displayid(const struct di_edid_ext *ext)
+{
+	if (ext->tag != DI_EDID_EXT_DISPLAYID) {
+		return NULL;
+	}
+	return &ext->displayid;
+}

include/bits.h

@@ -5,6 +5,7 @@
  * Utility functions to operate on bits.
  */
 
+#include <assert.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>

include/displayid.h

@@ -0,0 +1,24 @@
+#ifndef DISPLAYID_H
+#define DISPLAYID_H
+
+/**
+ * Private header for the low-level DisplayID API.
+ */
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <libdisplay-info/displayid.h>
+
+#include "log.h"
+
+struct di_displayid {
+	int version, revision;
+};
+
+bool
+_di_displayid_parse(struct di_displayid *displayid, const uint8_t *data,
+		    size_t size, struct di_logger *logger);
+
+#endif

include/edid.h

@@ -12,6 +12,7 @@
 #include <libdisplay-info/edid.h>
 
 #include "cta.h"
+#include "displayid.h"
 
 /**
  * The maximum number of EDID blocks (including the base block), defined in
@@ -96,6 +97,8 @@ struct di_edid_ext {
 	enum di_edid_ext_tag tag;
 	/* Used for DI_EDID_EXT_CEA */
 	struct di_edid_cta cta;
+	/* Used for DI_EDID_EXT_DISPLAYID */
+	struct di_displayid displayid;
 };
 
 /**

include/libdisplay-info/displayid.h

@@ -0,0 +1,29 @@
+#ifndef DI_DISPLAYID_H
+#define DI_DISPLAYID_H
+
+/**
+ * libdisplay-info's low-level API for VESA Display Identification Data
+ * (DisplayID).
+ *
+ * The library implements DisplayID version 1.3, available at:
+ * https://vesa.org/vesa-standards/
+ */
+
+/**
+ * DisplayID data structure.
+ */
+struct di_displayid;
+
+/**
+ * Get the DisplayID version.
+ */
+int
+di_displayid_get_version(const struct di_displayid *displayid);
+
+/**
+ * Get the DisplayID revision.
+ */
+int
+di_displayid_get_revision(const struct di_displayid *displayid);
+
+#endif

include/libdisplay-info/edid.h

@@ -614,6 +614,9 @@ enum di_edid_ext_tag {
 	DI_EDID_EXT_BLOCK_MAP = 0xF0,
 	/* Extension defined by the display manufacturer */
 	DI_EDID_EXT_VENDOR = 0xFF,
+
+	/* DisplayID Extension */
+	DI_EDID_EXT_DISPLAYID = 0x70,
 };
 
 /**
@@ -638,4 +641,15 @@ struct di_edid_cta;
 const struct di_edid_cta *
 di_edid_ext_get_cta(const struct di_edid_ext *ext);
 
+/* See <libdisplay-info/displayid.h> */
+struct di_displayid;
+
+/**
+ * Get a DisplayID extension block.
+ *
+ * Returns NULL if the extension block tag is not DI_EDID_EXT_DISPLAYID.
+ */
+const struct di_displayid *
+di_edid_ext_get_displayid(const struct di_edid_ext *ext);
+
 #endif

meson.build

@@ -36,6 +36,7 @@ di_lib = library(
 	'display-info',
 	[
 		'cta.c',
+		'displayid.c',
 		'dmt-table.c',
 		'edid.c',
 		'info.c',

test/data/apple-xdr-dp.diff

@@ -1,15 +1,6 @@
 --- ref
 +++ di
-@@ -31,7 +31,7 @@
-                  Hfront    8 Hsync  32 Hback   40 Hpol P
-                  Vfront   43 Vsync   8 Vback    6 Vpol N
-     Display Product Name: 'ProDisplayXDR'
--  Extension blocks: 6
-+  Extension blocks: 1
- Checksum: 0xeb
- 
- ----------------
-@@ -62,171 +62,16 @@
+@@ -62,171 +62,38 @@
      DTD 6:  3840x2160   47.951737 Hz  16:9    134.696 kHz    528.010000 MHz (699 mm x 393 mm)
                   Hfront    8 Hsync  32 Hback   40 Hpol P
                   Vfront   59 Vsync   8 Vback  582 Vpol N
@@ -18,8 +9,8 @@
  
  ----------------
  
--Block 2, DisplayID Extension Block:
--  Version: 1.2
+ Block 2, DisplayID Extension Block:
+   Version: 1.2
 -  Extension Count: 0
 -  Display Product Type: Extension Section
 -  ContainerID Data Block:
@@ -60,12 +51,12 @@
 -               Hfront    8 Hsync  32 Hback   28 Hpol P
 -               Vfront  118 Vsync   8 Vback    6 Vpol N
 -  Checksum: 0x8c
--Checksum: 0x90
--
------------------
--
--Block 3, DisplayID Extension Block:
--  Version: 1.2
+ Checksum: 0x90
+ 
+ ----------------
+ 
+ Block 3, DisplayID Extension Block:
+   Version: 1.2
 -  Extension Count: 0
 -  Video Timing Modes Type 1 - Detailed Timings Data Block:
 -    DTD:  2560x2880   59.999451 Hz   0:0    179.578 kHz    481.270000 MHz (aspect undefined, no 3D stereo)
@@ -84,12 +75,12 @@
 -               Hfront    8 Hsync  32 Hback   80 Hpol P
 -               Vfront  850 Vsync   8 Vback    6 Vpol N
 -  Checksum: 0x93
--Checksum: 0x90
--
------------------
--
--Block 4, DisplayID Extension Block:
--  Version: 1.2
+ Checksum: 0x90
+ 
+ ----------------
+ 
+ Block 4, DisplayID Extension Block:
+   Version: 1.2
 -  Extension Count: 0
 -  Video Timing Modes Type 1 - Detailed Timings Data Block:
 -    DTD:  3008x3384   59.999726 Hz   0:0    210.959 kHz    648.910000 MHz (aspect undefined, no 3D stereo)
@@ -108,12 +99,12 @@
 -               Hfront    8 Hsync  32 Hback   28 Hpol P
 -               Vfront 1001 Vsync   8 Vback    6 Vpol N
 -  Checksum: 0x7e
--Checksum: 0x90
--
------------------
--
--Block 5, DisplayID Extension Block:
--  Version: 1.2
+ Checksum: 0x90
+ 
+ ----------------
+ 
+ Block 5, DisplayID Extension Block:
+   Version: 1.2
 -  Extension Count: 0
 -  Video Timing Modes Type 1 - Detailed Timings Data Block:
 -    DTD:  5120x2880   59.999614 Hz  16:9    179.579 kHz    933.810000 MHz (aspect 16:9, no 3D stereo)
@@ -132,12 +123,12 @@
 -               Hfront    8 Hsync  32 Hback   40 Hpol P
 -               Vfront  850 Vsync   8 Vback    6 Vpol N
 -  Checksum: 0x0a
--Checksum: 0x90
--
------------------
--
--Block 6, DisplayID Extension Block:
--  Version: 1.2
+ Checksum: 0x90
+ 
+ ----------------
+ 
+ Block 6, DisplayID Extension Block:
+   Version: 1.2
 -  Extension Count: 0
 -  Video Timing Modes Type 1 - Detailed Timings Data Block:
 -    DTD:  6016x3384   59.999899 Hz  16:9    210.960 kHz   1286.010000 MHz (aspect 16:9, no 3D stereo, preferred)
@@ -156,10 +147,10 @@
 -               Hfront    8 Hsync  32 Hback   40 Hpol P
 -               Vfront 1001 Vsync   8 Vback    6 Vpol N
 -  Checksum: 0xb4
--Checksum: 0x90
--
------------------
--
+ Checksum: 0x90
+ 
+ ----------------
+ 
 -Warnings:
 -
 -Block 1, CTA-861 Extension Block:
@@ -167,8 +158,8 @@
 -Block 2, DisplayID Extension Block:
 -  Vendor-Specific Data Block (0x7f) (Apple), OUI 00-10-FA: Expected PNP ID but found OUI.
 -
- Failures:
- 
+-Failures:
+-
 -Block 1, CTA-861 Extension Block:
 -  Required 640x480p60 timings are missing in the established timings and the SVD list (VIC 1).
 -  Missing VCDB, needed for Set Selectable RGB Quantization to avoid interop issues.
@@ -181,10 +172,5 @@
 -EDID:
 -  DisplayID: Missing DisplayID Product Identification Data Block.
 -
-+Block 0, Base EDID:
-+  Unknown Extension Block.
-+  Unknown Extension Block.
-+  Unknown Extension Block.
-+  Unknown Extension Block.
-+  Unknown Extension Block.
- EDID conformity: FAIL
+-EDID conformity: FAIL
++EDID conformity: PASS