linux-kernel - Re: [PATCH v2 0/2] Add support for eGPUs on Apple Products

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Message-ID: <aXoxpWFE0rByjS-y@wunner.de>
Date: Wed, 28 Jan 2026 16:56:21 +0100
From: Lukas Wunner <lukas@...ner.de>
To: Atharva Tiwari <atharvatiwarilinuxdev@...il.com>
Cc: Ard Biesheuvel <ardb@...nel.org>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Tvrtko Ursulin <tursulin@...ulin.net>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Javier Martinez Canillas <javierm@...hat.com>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Lenny Szubowicz <lszubowi@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Francesco Pompo <francescopompo2@...il.com>,
	linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
	intel-gfx@...ts.freedesktop.org, intel-xe@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 0/2] Add support for eGPUs on Apple Products

On Wed, Jan 28, 2026 at 02:58:36PM +0000, Atharva Tiwari wrote:
> This series adds support for eGPUs on Apple products, by
> enabling apple-set-os on all apple devices.
> 
> A side effect of this patch is that the iGPU becomes enabled on iMacs.
> However, iMacs can’t use the iGPU to drive the display
> (They can't link-train the internal display),
> so displays must be disabled on iMacs.

Oh there's the explanation that should have been in the commit message
of patch [2/2].

It's possible that the iMac has a multiplexer built-in which can
switch between the iGPU and dGPU at runtime.  Please ensure that
you have set CONFIG_APPLE_GMUX=y in your .config, the gmux driver
should bind to the multiplexer if there is one.

If there is a multiplexer built-in, then disabling the iGPU is the
wrong approach.

Thanks,

Lukas