linux-kernel - Re: [PATCH v2] efi: libstub: add support for the apple_set

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Message-ID:
 <MA0P287MB0217E9997DD69512C71BB2BEB8D32@MA0P287MB0217.INDP287.PROD.OUTLOOK.COM>
Date: Mon, 1 Jul 2024 06:52:57 +0000
From: Aditya Garg <gargaditya08@...e.com>
To: Ard Biesheuvel <ardb@...nel.org>
CC: Lukas Wunner <lukas@...ner.de>, Hans de Goede <hdegoede@...hat.com>, Linux
 Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>, Kerem Karabay
	<kekrby@...il.com>, Orlando Chamberlain <orlandoch.dev@...il.com>
Subject: Re: [PATCH v2] efi: libstub: add support for the apple_set_os
 protocol



> On 1 Jul 2024, at 11:26 AM, Ard Biesheuvel <ardb@...nel.org> wrote:
> 
> On Mon, 1 Jul 2024 at 07:50, Lukas Wunner <lukas@...ner.de> wrote:
>> 
>>> On Mon, Jul 01, 2024 at 07:38:38AM +0200, Ard Biesheuvel wrote:
>>> Any thoughts on whether this should depend on CONFIG_APPLE_GMUX or not?
>> 
>> I tend towards *not* making it depend on CONFIG_APPLE_GMUX:
>> 
>> * The gpu-switch utility Orlando linked to doesn't use the apple-gmux
>>  driver.  (It changes EFI variables that influence to which GPU the
>>  EFI driver will switch on next reboot.)
>> 
>> * apple_set_os() has side effects beyond exposing the iGPU (such as
>>  switching the keyboard+trackpad access method to SPI instead of USB).
>>  If there are issues, they will be harder to debug if their occurrence
>>  depends on a Kconfig option.
> 
> Understood. I agree that having fewer possible combinations is
> strongly preferred.
> 
> However, this change affects all Intel Macs. Is the latter side effect
> likely to cause any regressions on Intel Mac users that don't have two
> GPUs to begin with?

It doesn't affect T2 Macs without dual GPU, I'm not sure about other Macs, although I doubt it would cause a regression. Although of the reasons of adding a parameter was this concern as well.