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!
> When an external DisplayPort source is added/removed, the following ACPI
> code is invoked:
>
> Scope (\_SB.PCI0.LPCB.SMC)
> {
> Device (DPPT)
> {
> Name (_HID, EisaId ("APP000C")) // _HID: Hardware ID
> Name (_CID, "smc-dppt") // _CID: Compatible ID
> }
> }
>
> Scope (\_SB.PCI0.LPCB.EC)
> {
> Method (_Q30, 0, NotSerialized) // _Qxx: EC Query
> {
> Notify (\_SB.PCI0.LPCB.SMC.DPPT, 0x80) // Status Change
> }
>
> Method (_Q31, 0, NotSerialized) // _Qxx: EC Query
> {
> Notify (\_SB.PCI0.LPCB.SMC.DPPT, 0x81) // Information Change
> }
> }
>
>
> I've already verified that the method calls do indeed take place, by
> turning on EC debugging. The APP000C device does also exist in /sys.
>
> 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.
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?
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.
Thanks,
Lukas
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