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Devices sharing a reset GPIO could use the reset framework for coordinated handling of that shared GPIO line. We have several cases of such needs, at least for Devicetree-based platforms. If Devicetree-based device requests a reset line, while "resets" Devicetree property is missing but there is a "reset-gpios" one, instantiate a new "reset-gpio" platform device which will handle such reset line. This allows seamless handling of such shared reset-gpios without need of changing Devicetree binding [1]. To avoid creating multiple "reset-gpio" platform devices, store the Devicetree "reset-gpios" GPIO specifiers used for new devices on a linked list. Later such Devicetree GPIO specifier (phandle to GPIO controller, GPIO number and GPIO flags) is used to check if reset controller for given GPIO was already registered. If two devices have conflicting "reset-gpios" property, e.g. with different ACTIVE_xxx flags, this would allow to spawn two separate "reset-gpio" devices, where the second would fail probing on busy GPIO request. Link: https://lore.kernel.org/all/YXi5CUCEi7YmNxXM@robh.at.kernel.org/ [1] Cc: Bartosz Golaszewski <brgl@bgdev.pl> Cc: Chris Packham <chris.packham@alliedtelesis.co.nz> Cc: Sean Anderson <sean.anderson@seco.com> Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> Acked-by: Linus Walleij <linus.walleij@linaro.org> Link: https://lore.kernel.org/r/20240129115216.96479-5-krzysztof.kozlowski@linaro.org Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
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.
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.