7d93aecdb5
Some SPI master controllers always drive a native chip select when performing a transfer. Hence when using both native and GPIO chip selects, at least one native chip select must be left unused, to be driven when performing transfers with slave devices using GPIO chip selects. Currently, to find an unused native chip select, SPI controller drivers need to parse and process cs-gpios theirselves. This is not only duplicated in each driver that needs it, but also duplicates part of the work done later at SPI controller registration time. Note that this cannot be done after spi_register_controller() returns, as at that time, slave devices may have been probed already. Hence add generic support to the SPI subsystem for finding an unused native chip select. Optionally, this unused native chip select, and all other in-use native chip selects, can be validated against the maximum number of native chip selects available on the controller hardware. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Link: https://lore.kernel.org/r/20200102133822.29346-2-geert+renesas@glider.be Signed-off-by: Mark Brown <broonie@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.