Technically touchscreen chip is FT5406 but all hardware
communication is performed by VideCore and only final results
are presented to ARM part through memory region shared between
VC and ARM.
evdev is used as userland interface. FT5406 supports up to
10 touchpoints, but for now driver emulates single touch device
because I do not have GUI bits to test this functionality.
Driver is not enabled in default config for RPI and RPI2
Tested with: evdev-dump, tslib
(1) Invoke cpp to bring in files via #include (although the old
/include/ stuff is supported still).
(2) bring in files from either vendor tree or freebsd-custom files
when building.
(3) move all dts* files from sys/boot/fdt/dts to
sys/boot/fdt/dts/${MACHINE} as appropriate.
(4) encode all the magic to do the build in sys/tools/fdt/make_dtb.sh
so that the different places in the tree use the exact same logic.
(5) switch back to gpl dtc by default. the bsdl one in the tree has
significant issues not easily addressed by those unfamiliar with
the code.
