linux-kernel - Re: [PATCH v3 0/2] efi/x86: Call set

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Message-ID:
 <MA0P287MB0217753D93980EB617739103B8AA2@MA0P287MB0217.INDP287.PROD.OUTLOOK.COM>
Date: Wed, 24 Jul 2024 16:34:02 +0000
From: Aditya Garg <gargaditya08@...e.com>
To: Lukas Wunner <lukas@...ner.de>
CC: Ard Biesheuvel <ardb@...nel.org>, "linux-efi@...r.kernel.org"
	<linux-efi@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Hans de Goede <hdegoede@...hat.com>, Kerem
 Karabay <kekrby@...il.com>, Orlando Chamberlain <orlandoch.dev@...il.com>,
	"sharpenedblade@...ton.me" <sharpenedblade@...ton.me>
Subject: Re: [PATCH v3 0/2] efi/x86: Call set_os() protocol on dual GPU Macs



> On 24 Jul 2024, at 10:01 PM, Lukas Wunner <lukas@...ner.de> wrote:
> 
> On Wed, Jul 24, 2024 at 04:26:58PM +0000, Aditya Garg wrote:
>>>> On 24 Jul 2024, at 9:31 PM, Lukas Wunner <lukas@...ner.de> wrote:
>>> I note that on x86, the efistub walks over all PCI devices in the system
>>> (see setup_efi_pci() in drivers/firmware/efi/libstub/x86-stub.c) and
>>> retrieves the Device ID and Vendor ID.  We could additionally retrieve
>>> the Class Code and count the number of GPUs in the system by checking
>>> whether the Class Code matches PCI_BASE_CLASS_DISPLAY.  If there's
>>> at least 2 GPUs in the system, invoke apple_set_os.
>> 
>> This also looks like a good idea, but I'm not well aware of the pci
>> quirks in the Linux kernel. So, would consider it a bug report for
>> the maintainers to fix.
> 
> This is not a PCI quirk in the kernel.  The efistub is a separate
> program.  I'm saying that the efistub already walks over all PCI devices,
> it would be trivial to hook into this to count GPUs, recognize the T2
> device or do something else entirely.
> 

I'll leave this to Ard. I'm really confused in choosing the best possible option here.

> Thanks,
> 
> Lukas