On Sat, Jun 14, 2025 at 09:04:52AM +0200, Lukas Wunner wrote: > On Fri, Jun 13, 2025 at 04:47:20PM -0500, Daniel Dadap wrote: > > Ideally we'd be able to actually query which GPU is connected to the panel > > at the time we're making this determination, but I don't think there's a > > uniform way to do this at the moment. Selecting the integrated GPU seems > > like a reasonable heuristic, since I'm not aware of any systems where the > > internal panel defaults to dGPU connection, since that would defeat the > > purpose of having a hybrid GPU system in the first place > > Intel-based dual-GPU MacBook Pros boot with the panel switched to the > dGPU by default. This is done for Windows compatibility because Apple > never bothered to implement dynamic GPU switching on Windows. > > The boot firmware can be told to switch the panel to the iGPU via an > EFI variable, but that's not something the kernel can or should depend on. > > MacBook Pros introduced since 2013/2014 hide the iGPU if the panel is > switched to the dGPU on boot, but the kernel is now unhiding it since > 71e49eccdca6. > > I don't pretend to fully understand the consequences of the proposed > patch, just want to highlight the regression potential on Apple machines > and probably others. This is good to know. Is vga_switcheroo initialized by the time the code in this patch runs? If so, maybe we should query switcheroo to determine the GPU which is connected to the panel and favor that one, then fall back to the "iGPU is probably right" heuristic otherwise. > > Thanks, > > Lukas
