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Some SPI/QuadSPI controllers only expose a high-level SPI memory interface, thus preventing any regular SPI transfers from being done. In that case, SPI controller drivers can leave all ->transfer_xxx() hooks empty and only implement the spi_mem_ops interface. Adjust the core to allow such situations: - extend spi_controller_check_ops() to accept situations where all ->transfer_xxx() pointers are NULL only if ->mem_ops != NULL - make sure we do not initialize the SPI message queue if ctlr->transfer_one and ctlr->transfer_one_message are missing - return -ENOTSUPP if someone tries to do a regular SPI transfer on a controller that does not support it Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com> Reviewed-by: Frieder Schrempf <frieder.schrempf@exceet.de> Tested-by: Frieder Schrempf <frieder.schrempf@exceet.de> 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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.