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Mainline Linux tree for various devices, only for fun :)
fa38869b01
This concerns gpio edge detection for GPIO IRQs used from
userspace for GPIO event listeners.
Trying to work out the right event if it's not sure that the
examined gpio actually moved is impossible.
Consider two gpios "gpioA" and "gpioB" that share an interrupt.
gpioA's irq should trigger on any edge, gpioB's on a falling edge.
If now the common irq fires and both gpio lines are high, there
are several possibilities that could have happend:
a) gpioA just had a low-to-high edge
b) gpioB just had a high-to-low-to-high spike
c) a combination of both a) and b)
While c) is unlikely (in most setups) a) and b) alone are bad
enough. Currently the code assumes case a) unconditionally and
doesn't report an event for gpioB. Note that even if there is no
irq sharing involved a spike for a gpio might not result in an
event if it's configured to trigger for a single edge only.
The only way to improve this is to drop support for interrupt
sharing. This way a spike results in an event for the right gpio
at least. Note that apart from dropping IRQF_SHARED this
effectively undoes commit
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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.