Run the device tree overlays through the preprocessor before compiling it, as
is done in the kernel. This helps make overlays easier to understand, and
improves compatibility with those found in the wild.
I found the correct command line by running the kernel build with V=1, and then
removing all the arguments related to dependency tracking.
Since dtc 1.4.7 (released in 2018), there has been a much nicer syntax for
device tree overlays. This commit converts the dtsText example to use this
syntax.
The `platform` field is pointless nesting: it's just stuff that happens
to be defined together, and that should be an implementation detail.
This instead makes `linux-kernel` and `gcc` top level fields in platform
configs. They join `rustc` there [all are optional], which was put there
and not in `platform` in anticipation of a change like this.
`linux-kernel.arch` in particular also becomes `linuxArch`, to match the
other `*Arch`es.
The next step after is this to combine the *specific* machines from
`lib.systems.platforms` with `lib.systems.examples`, keeping just the
"multiplatform" ones for defaulting.
Now allows applying external overlays either in form of
.dts file, literal dts context added to store or precompiled .dtbo.
If overlays are defined, kernel device-trees are compiled with '-@'
so the .dtb files contain symbols which we can reference in our
overlays.
Since `fdtoverlay` doesn't respect `/ compatible` by itself
we query compatible strings of both `dtb` and `dtbo(verlay)`
and apply only if latter is substring of the former.
Also adds support for filtering .dtb files (as there are now nearly 1k
dtbs).
Co-authored-by: georgewhewell <georgerw@gmail.com>
Co-authored-by: Kai Wohlfahrt <kai.wohlfahrt@gmail.com>
This can be used to explicitly specify a specific dtb file, relative to
the dtb base.
Update the generic-extlinux-compatible module to make use of this option.
Add support for custom device-tree files, and applying overlays to them.
This is useful for supporting non-discoverable hardware, such as sensors
attached to GPIO pins on a Raspberry Pi.
