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I have ACPICA working in my os. I know that using ACPI I can access EDID data. Is this always true? Or it works only for some special case (assuming that both ACPI and EDID are present on the system/monitor)?

Hi,

AlfaOmega08 wrote:I have ACPICA working in my os. I know that using ACPI I can access EDID data. Is this always true? Or it works only for some special case (assuming that both ACPI and EDID are present on the system/monitor)?

Sorry - I haven't really looked into ACPI's AML (it's useless during boot, and I have no intention of using it after boot). I did take a look at the ACPI specification/s though:

ACPI wrote:B.1 Introduction

This section of the document describes a number of specialized ACPI methods to support motherboard graphics devices.

In many cases, system manufacturers need to add special support to handle multiple output devices such as panels and TV-out capabilities, as well as special power management features. This is particularly true for notebook manufacturers. The methods described here have been designed to enable interaction between the system BIOS, video driver, and OS to smoothly support these features.

Systems containing a built-in display adapter are required to implement the ACPI Extensions for Display Adapters.

A few years ago I disassembled ACPI's AML on about 3 of the computers here, and don't recall seeing anything about any video devices or EDID. Today I disassembled the AML on this computer and found nothing about any video devices or EDID. As far as I can tell (at least for Intel's built-in display adapters) it behaves the same as a normal video card as far as ACPI is concerned.

This gives me the opinion that AML for EDID is only used for computers with built-in LCD screens (and isn't used for computers with built-in graphics adapter/s and external monitors, which makes a little sense because a BIOS manufacturer can't hard-code EDID data for an external/unknown monitor into the firmware); and therefore isn't used on desktop/server computers at all.


Cheers,

Brendan