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commit73f3bc6da5upstream. The SPI interface implementation was completely broken. When using the SPI interface, there are only 7 address bits, the upper bit is controlled by a page select register. The core needs access to both ranges, so implement register read/write for both regions. The regmap paging functionality didn't agree with a register that needs to be read and modified, so I implemented a custom paging algorithm. This fixes that the device wouldn't even probe in SPI mode. The SPI interface then isn't different from I2C, merged them into the core, and the I2C/SPI named registers are no longer needed. Implemented register value caching for the registers to reduce the I2C/SPI data transfers considerably. The calibration set reads as all zeroes until some undefined point in time, and I couldn't determine what makes it valid. The datasheet mentions these registers but does not provide any hints on when they become valid, and they aren't even enumerated in the memory map. So check the calibration and retry reading it from the device after each measurement until it provides something valid. Despite the size this is suitable for a stable backport given that it seems the SPI support never worked. Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl> Fixes:1b3bd85927("iio: chemical: Add support for Bosch BME680 sensor"); Cc: <Stable@vger.kernel.org> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.