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a9e9c7153e
This adds max1117/max1118/max1119 8-bit, dual-channel ADC driver. This new driver uses the zero length spi_transfers with the cs_change flag set and/or the non-zero delay_usecs. 1. The zero length transfer with the spi_transfer.cs_change set is required in order to select CH1. The chip select line must be brought high and low again without transfer. 2. The zero length transfer with the spi_transfer.delay_usecs > 0 is required for waiting the conversion to be complete. The conversion begins with the falling edge of the chip select. During the conversion process, SCLK is ignored. These two usages are unusual. But the spi controller drivers that use a default implementation of transfer_one_message() are likely to work. (I've tested this adc driver with spi-omap2-mcspi and spi-xilinx) On the other hand, some spi controller drivers that have their own transfer_one_message() may not work. But at least for the zero length transfer with delay_usecs > 0, I'm proposing a new testcase for the spi-loopback-test that can test whether the delay_usecs setting has taken effect. Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Cc: Jonathan Cameron <jic23@kernel.org> Cc: Hartmut Knaack <knaack.h@gmx.de> Cc: Lars-Peter Clausen <lars@metafoo.de> Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net> Cc: Rob Herring <robh+dt@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mark Brown <broonie@kernel.org> Signed-off-by: Jonathan Cameron <jic23@kernel.org> |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.