7547b5969e
Apart from the usual stuff, the debugfs code is currently also used for one non-obvious side effect. It attempts to check whether the chip's registers are still set to an expected value, and if not, re-initializes them. It seems that the driver has "always" done so. The code, however, also checks the INTF register which normally indicates which pins have caused the recent interrupt. That's a volatile register, and the datasheet says that writes are ignored in there. When I'm just cat-ing /sys/kernel/debug/gpio with no SPI traffic and no nosie on the GPIO lines, I'm not getting any warnings. Once I actually use these GPIOs and cat that file in parallel, I always seem to get a: mcp23s08 spi1.1: restoring reg 0x07 from 0x0000 to 0xffff (power-loss?) This might be a sign that I should not leave my unused inputs floating, but the code should not be checking a volatile register, anyway. Let's simply skip this last item in the iteration. I was also considering removing this enitre re-initialization because it's non-obvious, but the code survived various refactorings already and has sign-offs by people who know more than I do, so let's leave it as-is. For now :). Signed-off-by: Jan Kundrát <jan.kundrat@cesnet.cz> Reviewed-by: Phil Reid <preid@electromag.com.au> Signed-off-by: Linus Walleij <linus.walleij@linaro.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.