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.

Changes in v2:
- Reworded cover-letter
- Transferred logic to has_no_display in the 2nd patch

Link to v1:
https://lore.kernel.org/all/20260125001111.1269-1-atharvatiwarilinuxdev@gmail.com/

Atharva Tiwari (2):
  efi/libstub: enable apple-set-os for all apple devices
  drm/i915/display: Disable display for iMac's

 drivers/firmware/efi/libstub/x86-stub.c       | 22 +++++--------------
 .../drm/i915/display/intel_display_device.c   | 13 ++++++++++-
 2 files changed, 17 insertions(+), 18 deletions(-)

-- 
2.43.0

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

> 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.

I was using apple-gmux even before this patch, and runtime GPU switching
does not work on either macOS or Linux.
On macOS, the iGPU does not even appear in System Information.
However, the iGPU is present in IORegistry, and Apple appears to use it
only for acceleration, not for display output. This can be seen from
the following IORegistry entry:

    | |   | +-o AppleIntelFramebufferController  <class AppleIntelFramebufferController, id 0x100000556, registered, matched, active, busy 0 (230 ms), retain 8>
    | |   | | |   "IOClass" = "AppleIntelFramebufferController"
    | |   | | |   "IOPersonalityPublisher" = "com.apple.driver.AppleIntelCFLGraphicsFramebuffer"
    | |   | | |   "CFBundleIdentifierKernel" = "com.apple.driver.AppleIntelCFLGraphicsFramebuffer"
    | |   | | |   "CFBundleIdentifier" = "com.apple.driver.AppleIntelCFLGraphicsFramebuffer"
    | |   | | |   "IOMatchCategory" = "IOFramebuffer"
    | |   | | |   "NumFrameBuffer" = <00>

NumFrameBuffer=0 says that iGPU isint handling any dispaly atm.