On 12.05.2017 12:06, Lukas Wunner wrote: > On Fri, May 12, 2017 at 10:37:47AM +0200, Florian Echtler wrote: >> I'm currently adding support for the iMac's target display mode (TDM) to >> Linux. > > Cool! :-) >> However, I'm not seeing anything happening with either acpi_listen or >> kacpimon. >> Does this require any kernel changes, or could I subscribe to these >> events somehow? > > You can subscribe to these events by calling acpi_install_notify_handler(). > See drivers/platform/x86/apple-gmux.c for an example. That's a driver for > APP000B, a custom chip found on dual-GPU MacBook Pros dubbed GMUX which is > responsible for multiplexing the panel between the GPUs. OK, but this has to happen in a kernel context, correct? No way to see these from userspace? > I'm not sure what APP000C is, could be a similar custom controller, I'd have > to do some research first to know what it does. Surely "DP" stands for > DisplayPort, but what does "PT" stand for? I'm guessing DPPT is for "DisPlayPorT". As far as I could tell, it's just a stub for receiving the Notify() calls; the actual source switching is handled by writing to SMC keys. > Perhaps apple-gmux.c could serve as a template for an APP000C driver. > The code should be easy to understand, if you have questions just ask away. Since I need to modify the applesmc.c driver anyway, it would probably make sense to integrate the notify handler there? The other approach would be to write a dedicated TDM module, but I'm not sure how to access the SMC, then... Best, Florian -- SENT FROM MY DEC VT50 TERMINAL
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