readme: List the relevant specifications and where to get them

Signed-off-by: Sebastian Wick <sebastian.wick@redhat.com>

README.md

@@ -36,6 +36,63 @@ particular, each commit must carry a Signed-off-by tag to denote that the
 submitter adheres to the [Developer Certificate of Origin 1.1]. This project
 follows the [freedesktop.org Contributor Covenant].
 
+## Specifications
+
+Both EDID and DisplayID are defined by VESA and the specifications are publicly
+available. There are multiple versions defined and they have multiple
+mechanisms for extending the base specification. Some of the extensions also
+have mechanisms for additional extensions. This sometimes makes it hard to find
+where a particular data structure is defined.
+
+The raw data is usually read from the Display Data Channel (DDC) but other
+methods of delivery exist.
+
+Available freely [from VESA directly] are the base EDID specifications, VESA
+specified EDID extensions, as well as the base DisplayID specifications. EDID
+also specifies how DisplayID can be embedded in EDID.
+
+* VESA Enhanced Extended Display Identification Data (E-EDID) Standard;
+  Release A, Revision 1; February 9, 2000; Defines EDID Structure Version 1,
+  Revision 3
+* VESA Enhanced Extended Display Identification Data (E-EDID) Standard;
+  Release A, Revision 2; September 25, 2006; Defines EDID Structure Version 1,
+  Revision 4
+* VESA Video Timing Block Extension Data (VTB-EXT) Standard; Release A;
+  November 24, 2003
+* VESA Enhanced EDID Localized String Extension Standard; Release A;
+  July 10, 2003
+* VESA Display Transfer Characteristics Data Block (DTCDB) Standard;
+  Version 1.0; August 31, 2006
+* VESA Display Information Extension Block (DI-EXT) Standard; Release A;
+  August 21, 2001
+* VESA Display Device Data Block (DDDB) Standard; Version 1;
+  September 25, 2006
+* VESA Display Identification Data (DisplayID) Standard; Version 1.3;
+  July 5, 2013
+* VESA Display Identification Data (DisplayID) Standard; Version 2.0;
+  11 September, 2017
+* VESA Display Identification Data (DisplayID) Standard; Version 2.1;
+  18 November, 2021
+* VESA Display Identification Data (DisplayID) Standard; Version 2.1a;
+  18 March, 2024
+
+The most common extension to both EDID and DisplayID is CTA-861 which can be
+downloaded for free [from CTA].
+
+* A DTV Profile for Uncompressed High Speed Digital Interfaces
+  (CTA-861-E, CTA-861-F, CTA-861-G, CTA-861-H, CTA-861-I)
+* HDR Static Metadata Extensions (CTA-861.3-A)
+
+The CTA-861 specification allows for Vendor Specific Data Blocks (VSDB). Their
+specifications are often proprietary and have to be reverse engineered. Some
+specifications are available publicly.
+
+* HDMI and HDMI Forum VSDB are specified in the HDMI specification
+* Microsoft EDID Extension for [HMDs and Specialized Monitors]
+
+The libdisplay-info structures of the low-level API always point to the
+relevant specification and section therein.
+
 ## Building
 
 libdisplay-info has the following dependencies:
@@ -74,6 +131,9 @@ To fuzz libdisplay-info with [AFL], the library needs to be instrumented:
 [Wayland contribution guidelines]: https://gitlab.freedesktop.org/wayland/wayland/-/blob/main/CONTRIBUTING.md
 [Developer Certificate of Origin 1.1]: https://developercertificate.org/
 [freedesktop.org Contributor Covenant]: https://www.freedesktop.org/wiki/CodeOfConduct/
+[from VESA directly]: https://vesa.org/vesa-standards/
+[from CTA]: https://www.cta.tech/SearchResults?search=CTA-861
+[HMDs and Specialized Monitors]: https://learn.microsoft.com/en-us/windows-hardware/drivers/display/specialized-monitors-edid-extension
 [hwdata]: https://github.com/vcrhonek/hwdata
 [Meson]: https://mesonbuild.com/
 [coverage]: https://gitlab.freedesktop.org/emersion/libdisplay-info/-/jobs/artifacts/main/file/build/meson-logs/coveragereport/index.html?job=build-gcc