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The latched input feature of the pca953x GPIO controller is useful when an input is configured to trigger interrupts on rising or falling edges, because it allows retrieving which edge type caused a given interrupt even if the pin state changes again before the interrupt handler has a chance to run. But for level-triggered interrupts, reading the latched input state can cause an active interrupt condition to be missed, e.g. if an active-low signal (for which an IRQ_TYPE_LEVEL_LOW interrupt has been configured) triggers an interrupt when switching to the inactive state, but then becomes active again before the interrupt handler has a chance to run: in this case, if the interrupt handler reads the latched input state, it will wrongly assume that the interrupt is not pending. Fix the above issue by enabling the latch only on edge-triggered inputs, instead of all interrupt-enabled inputs. Signed-off-by: Francesco Lavra <flavra@baylibre.com> Reviewed-by: Ian Ray <ian.ray@gehealthcare.com> Reviewed-by: Martyn Welch <martyn.welch@collabora.com> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@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 reStructuredText 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.