Hi, On 2/19/23 14:39, Lukas Wunner wrote: > On Fri, Feb 17, 2023 at 11:05:31AM +1100, Orlando Chamberlain wrote: >> On Thu, 16 Feb 2023 14:27:13 +0100 Hans de Goede <hdegoede@xxxxxxxxxx> wrote: >> It looks like iMac20,1, iMac20,2, and iMacPro1,1 have APP000B: >> >> apple_gmux: Failed to find gmux I/O resource >> >> iMac20,2: https://linux-hardware.org/?probe=ec2af584b3&log=dmesg >> iMac20,1: https://linux-hardware.org/?probe=fee7644b9c&log=dmesg >> iMacPro1,1: https://linux-hardware.org/?probe=6c26c9ff8c&log=dmesg >> >> But I'm not sure if they actually have it or not. > > A number of iMacs support Target Display Mode, i.e. you can plug in > an external computer to the iMac's DisplayPort and use the iMac as > its screen. Those iMac models do contain a gmux to mux the display > between internal GPU and external DisplayPort connection. Linux > does not have support for this, sadly. It would require generalizing > vga_switcheroo for use cases beyond dual GPU laptops. Florian Echtler > has been looking into Target Display Mode but I'm not sure he got it > working: > > https://lore.kernel.org/all/e6b44662-8b05-fb8d-660e-77153680d11b@xxxxxxxxxxxxxx/ > https://lore.kernel.org/all/71a48bf5-54b5-6d7b-d574-e0aa6c1acb80@xxxxxxxxxxxxxx/ > https://lore.kernel.org/all/1497603751-22360-1-git-send-email-floe@xxxxxxxxxxxxxx/ > > I believe the Mac Pro (the trashcan one) also contains a gmux and > an APP000B device in DSDT. I recall seeing a bug report due to a > splat in the gmux driver on that machine. Back then I confirmed > in the schematics that it does contain a gmux, though I think it's > only used for brightness, not GPU switching. Erm, the Mac Pro (the trashcan one) does not have an internal LCD panel, right? So I don't think the gmux will be used for brightness control there ... Regards, Hans
