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>
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>
Update the gpio-mockup documentation to note that is has been
obsoleted by the gpio-sim.
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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>
Add documentation for v1 of the GPIO character device userspace API
to the obsolete section of 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>
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>
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>
There are only a handful of users of gpio_export() and
related functions.
As these are just wrappers around the modern gpiod_export()
helper, remove the wrappers and open-code the gpio_to_desc
in all callers to shrink the legacy API.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
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>
Implement a new, modern GPIO testing module controlled by configfs
attributes instead of module parameters. The goal of this driver is
to provide a replacement for gpio-mockup that will be easily extensible
with new features and doesn't require reloading the module to change
the setup.
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
First of all one of the parameter missed 'mockup' in its name,
Second, the semantics of the integer pairs depends on the sign
of the base (the first value in the pair).
Update documentation to reflect the real code behaviour.
Fixes: 2fd1abe99e ("Documentation: gpio: add documentation for gpio-mockup")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
There's some documentation for gpio-mockup's debugfs interface in the
driver's source but it's not much. Add proper documentation for this
testing module.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
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>
