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The GPIO subsystem used to have a serious problem with undefined behavior
and use-after-free bugs on hot-unplug of GPIO chips. This can be
considered a corner-case by some as most GPIO controllers are enabled
early in the boot process and live until the system goes down but most
GPIO drivers do allow unbind over sysfs, many are loadable modules that
can be (force) unloaded and there are also GPIO devices that can be
dynamically detached, for instance CP2112 which is a USB GPIO expender.
Bugs can be triggered both from user-space as well as by in-kernel users.
We have the means of testing it from user-space via the character device
but the issues manifest themselves differently in the kernel.
This is a proposition of adding a new virtual driver - a configurable
GPIO consumer that can be configured over configfs (similarly to
gpio-sim) or described on the device-tree.
This driver is aimed as a helper in spotting any regressions in
hot-unplug handling in GPIOLIB.
Link: https://lore.kernel.org/r/20240708142912.120570-1-brgl@bgdev.pl
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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The gpio-mockup has been obsoleted by the gpio-sim, so relocate its
documentation into the obsolete section of the admin-guide book.
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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Capitalise the title of the GPIO documentation page to match other
subsystems.
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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The GPIO sysfs API is long obsolete, so highlight this even further
by moving it into an obsolete APIs section in both the admin-guide
and userspace-api books.
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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Add documentation for the GPIO character device userspace API.
Added to the userspace-api book, but also provide a link from the
admin-guide book, as historically the GPIO documentation has been
there.
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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Include the gpio-sim.rst file in the GPIO index (toc/table of contents).
Quietens this doc build warning:
Documentation/admin-guide/gpio/gpio-sim.rst: WARNING: document isn't included in any toctree
Fixes: b48f6b466e44 ("gpio: sim: new testing module")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
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There's now a new ReST file. Add it to the index.rst file.
Fixes: ce7a2f77f976 ("docs: gpio: Add GPIO Aggregator documentation")
Fixes: 2fd1abe99e5f ("Documentation: gpio: add documentation for gpio-mockup")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Link: https://lore.kernel.org/r/bad4d85c218d59c1bf69157df8e1012577680d88.1601616399.git.mchehab+huawei@kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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Document the GPIO Aggregator, and the two typical use-cases.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Ulrich Hecht <uli+renesas@fpond.eu>
Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Link: https://lore.kernel.org/r/20200511145257.22970-6-geert+renesas@glider.be
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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While this is stated as obsoleted, the sysfs interface described
there is still valid, and belongs to the admin-guide.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
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