This provides an alternative esp32-specific SPI driver with ops that can be
swapped in place of the gpio bitbang one.
The pinmux info and lws gpio driver and other data in the spi bitbang
struct are used as-is by the DMA one.
New ops are provided which are able to allocate and free DMA-able memory so
the device drivers can prepare directly usable buffers. Bounce through to
DMA-able buffers is also transparently supported.
The old esp32 -factory stuff along with the lws support doesn't have a
future in its old form. It has users but the ratio of effort to
contribution is really especially bad. I haven't updated it for more
than a year since esp-idf changes broke the original stuff.
Freertos plat is alive and well and getting a lot of new use, ESP-32 is
supported both there and by modern lws_drivers pieces, including in CI
on real hardware, any further effort will be invested in that direction
instead of more vendor api-specific code (outside of wrapper
implementation).
lws_drivers wraps any SDK apis in generic lws apis such that your code
just uses those, enabling it to become SDK / SoC / vendor independent.
Its first implementation is on esp-idf, the low and mid-level features
that were in the old -factory are already available using that and
new technologies like lws_struct and Secure Streams.
Establish a new distributed CMake architecture with CMake code related to
a source directory moving to be in the subdir in its own CMakeLists.txt.
In particular, there's now one in ./lib which calls through to ones
further down the directory tree like ./lib/plat/xxx, ./lib/roles/xxx etc.
This cuts the main CMakelists.txt from 98KB -> 33KB, about a 66% reduction,
and it's much easier to maintain sub-CMakeLists.txt that are in the same
directory as the sources they manage, and conceal all the details that that
level.
Child CMakelists.txt become responsible for:
- include_directories() definition (this is not supported by CMake
directly, it passes it back up via PARENT_SCOPE vars in helper
macros)
- Addition child CMakeLists.txt inclusion, for example toplevel ->
role -> role subdir
- Source file addition to the build
- Dependent library path resolution... this is now a private thing
in the child CMakeLists.txt, it just passes back any adaptations
to include_directories() and the LIB_LIST without filling the
parent namespace with the details
