In general case. I2C Touch support in BIOS required maintain a touch/panel
matrix. This matrix included Panel ID, Touch I2C slave address, HID
Descriptor address and HID. At BIOS post, BIOS will read Panel ID from
Panel’s EDID for checking matrix and fill in necessary data into ACPI HID
fields for windows HID I2C class driver used.
Thus, if we can store I2C slave address and HID Descriptor address in EDID
unused fields, we can support more various Touch Panel without maintaining
original matrix in BIOS.
In the EDID data format, the standard timing information (bytes 38~53) and
Detailed Timing Descriptor (bytes 54 ~ 125) fields are allowed to define as
unused if unnecessary.
Note. For On-Cell and In-Cell type touch panels. Touch sensor is physically
build-in with LCD Panel. So, touch info in EDID data will unique and fixed.
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INC, HP, "FLEXIBLE EMBEDDED TOUCH PANEL SUPPORT VIA PANEL'S EDID", Technical Disclosure Commons, (August 09, 2019)