linux-kernel - Re: [PATCH 0/5] efi: x86: Provide EDID from GOP device

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Message-ID: <b6801420-6ae4-44cb-9d86-e9353a2a59d8@suse.de>
Date: Mon, 17 Nov 2025 09:01:56 +0100
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: jonathan@...ek.ca, javierm@...hat.com, linux-efi@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] efi: x86: Provide EDID from GOP device

Hi

Am 14.11.25 um 09:31 schrieb Ard Biesheuvel:
> On Wed, 15 Oct 2025 at 18:08, Thomas Zimmermann <tzimmermann@...e.de> wrote:
>> Add support for EFI_EDID_ACTIVE_PROTOCOL and EFI_EDID_DISCOVERED_PROTOCOL
>> on x86. Refactor the GOP helpers for EDID support, then retrieve the EDID
>> into x86 boot_params.
>>
>> Later boot code copies the EDID from the boot parameters into the global
>> variable edid_info. Graphics drivers, such as efidrm, can pick up the
>> information from there. In the case of efidrm, it provides the EDID to
>> user-space compositors, which use it for improved QoS on the display
>> output. Similar functionality is already available on old VESA systems
>> with vesadrm.
>>
>> Tested on x86 EFI systems.
>>
>> Another patch is required to provide EDID on non-x86 systems via the
>> generic EFI stub. The implementation can directly build upon this
>> series.
>>
>> Thomas Zimmermann (5):
>>    efi: Fix trailing whitespace in header file
>>    efi/libstub: gop: Find GOP handle instead of GOP data
>>    efi/libstub: gop: Initialize screen_info in helper function
>>    efi/libstub: gop: Add support for reading EDID
>>    efi/libstub: x86: Store EDID in boot_params
>>
> Hi,
>
> Apologies for the delay. This series looks fine to me, although I
> would prefer it if we could make things a bit more generic?
>
> Everything you are adding here is arch-agnostic, except for the bit
> where we use x86-specific plumbing to pass the EDID info between the
> EFI stub and the core kernel.

Attached is an RFC patch that I already have. This would be the next 
step for EDID support. I've not yet sent the generic-EFI patch, as I did 
not have opportunity to test it. The patch addresses most of what you 
ask for, I think.

>
> More specifically, could we do the following:
> - move struct edid_info edid_info into common code

edid_info is related to screen_info, so it follows the same conventions. 
Arnd Bergmann made x86-specific changes for screen_info in commit 
b8466fe82b79 ("efi: move screen_info into efi init code"). x86 has it's 
own thing, sort of. See the attached patch for my non-x86 solution.

> - pass the detected EDID info block via a EFI config table instead of
> boot_params

The x86 code uses boot params for screen_info already and also transfers 
edid_info on VESA systems via boot params (or if grub set up boot_params 
for us). [1] It's all there and working already. If we transfer 
edid_info via config table, we'd need extra code on x86.

> - make CONFIG_FIRMWARE_EDID depend on (X86 || EFI_STUB)

See the attached patch.

Best regards
Thomas


-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)


View attachment "0001-efi-transfer-EDID-from-stub-to-kernel.patch" of type "text/x-patch" (11641 bytes)