[Apple] MacBook8,1 keyboard/trackpad

["Stephan Günther" <moepi@moepi.net>]

The MacBook8,1 (12" retina model, not the 13" MacBookPro12,1) released
in April 2015 has no Linux support for its internal trackpad/keyboard so
far although the 13" model (MacBookPro12,1) recently got supported.

The problem is that the internal keyboard/trackpad is connected via SPI,
which differs from previous models.


However, according to all I figured out the internal keyboard/trackpad
of the MacBookPro12,1 is connected in precisely the same way:

1) OSX reports both as SPI devices, not USB.

2) Booting Linux the input devices magically show up as USB devices for
the MacBookPro12,1 but remain completely hidden on the MacBook8,1.


I tried to track the problem by mining various kernel modules with
printks. The result for *both* MacBooks:

1) Input devices are behind pci0000:00/0000:00:15.4 (the Intel Lynxpoint
/ Wildcat Point-LP SPI controler).

2) In the ACPI namespace the input devices are located at
PNP0A08:00/INT33C1:00/APP000D:00.

3) __acpi_match_device() is called with the APPLE-SPI-TOPCASE has hwid.
That is what's behind APP000D:00. But it returns NULL and the device is
not enabled.

Now, for any reason I do not understand (I have no idea of ACPI)
anything makes the touchpad controller (bcm5974), which is that
APPLE-SPI-TOPCASE, show up as USB device on the MacBookPro12,1. But on
the MacBook8,1 nothing happens.


Request for help: is it a firmware problem, a missing identifier in the
kernel sources, or is there really no Linux support at all? Maybe it is
not even a problem with ACPI at all...

I can provide you with any logs and even dunps of the DSDT.


Best,
Stephan