spi: Updates for v6.9

This release sees some exciting changes from David Lechner which
implements some optimisations that have been talked about for a long
time which allows client drivers to pre-prepare SPI messages for
repeated or low latency use.  This lets us move work out of latency
sensitive paths and avoid repeating work for frequently performed
operations.  As well as being useful in itself this will also be used in
future to allow controllers to directly trigger SPI operations (eg, from
interrupts).

Otherwise this release has mostly been focused on cleanups, plus a
couple of new devices:

 - Support for pre-optimising messages.
 - A big set of updates from Uwe Kleine-König moving drivers to use APIs
   with more modern terminology for controllers.
 - Major overhaul of the s3c64xx driver.
 - Support for Google GS101 and Samsung Exynos850.
spi: Introduce SPI_INVALID_CS and is_valid_cs()

The SPI core inconsistently uses the marker value for unused chip select
pin. Define a constant (with appropriate type) and introduce is_valid_cs()
helper function to avoid spreading this inconsistency in the future.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://msgid.link/r/20240307150256.3789138-4-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
1 file changed