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GPIO drivers call gpiochip_(un)lock_as_irq whenever they want to use a gpio as an interrupt. This is done when the irq is requested and it marks the gpio as in use by an interrupt. This is problematic for cases where a gpio pin is used as an interrupt pin, then, after the irq is disabled, is used as a regular gpio pin. Currently it is not possible to do this other than by first freeing the interrupt so gpiochip_unlock_as_irq is called, since an attempt to switch the gpio direction for output will fail since gpiolib believes that the gpio is in use for an interrupt and it does not know that it the irq is actually disabled. There are currently two drivers that would like to be able to do this: the tda998x_drv.c driver where a regular gpio pin needs to be temporarily reconfigured as an interrupt pin during CEC calibration, and the cec-gpio driver where you want to configure the gpio pin as an interrupt while waiting for traffic over the CEC bus, or as a regular pin when receiving or transmitting a CEC message. The solution is to add a new flag that is set when the irq is enabled, and have gpiod_direction_output check for that flag. We also add functions that drivers that do not use GPIOLIB_IRQCHIP can call when they enable/disable the irq. Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> |
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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.