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ca386253ff
The devicetree binding allows specifying which pins are GPIO vs LED. Limiting the instantiated gpiochip to just these pins as the driver currently does requires an arbitrary mapping between pins and GPIOs, but such a mapping is not implemented by the driver. As a result, specifying GPIOs in such a way that they don't map 1-to-1 to pin indexes does not function as expected. Establishing such a mapping is more complex than not and even if we did, doing so leads to a slightly hairy userspace experience as the behaviour of the PCA955x gpiochip would depend on how the pins are assigned in the devicetree. Instead, always expose all pins via the gpiochip to provide a stable interface and track which pins are in use. Specifying a pin as `type = <PCA955X_TYPE_GPIO>;` in the devicetree becomes a no-op. I've assessed the impact of this change by looking through all of the affected devicetrees as of the tag leds-5.15-rc1: ``` $ git grep -l 'pca955[0123]' $(find . -name dts -type d) arch/arm/boot/dts/aspeed-bmc-ibm-everest.dts arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts arch/arm/boot/dts/aspeed-bmc-opp-mihawk.dts arch/arm/boot/dts/aspeed-bmc-opp-mowgli.dts arch/arm/boot/dts/aspeed-bmc-opp-swift.dts arch/arm/boot/dts/aspeed-bmc-opp-tacoma.dts arch/arm/boot/dts/aspeed-bmc-opp-witherspoon.dts ``` These are all IBM-associated platforms. I've analysed both the devicetrees and schematics where necessary to determine whether any systems hit the hazard of the current broken behaviour. For the most part, the systems specify the pins as either all LEDs or all GPIOs, or at least do so in a way such that the broken behaviour isn't exposed. The main counter-point to this observation is the Everest system whose devicetree describes a large number of PCA955x devices and in some cases has pin assignments that hit the hazard. However, there does not seem to be any use of the affected GPIOs in the userspace associated with Everest. Regardless, any use of the hazardous GPIOs in Everest is already broken, so let's fix the interface and then fix any already broken userspace with it. Signed-off-by: Andrew Jeffery <andrew@aj.id.au> Acked-by: Linus Walleij <linus.walleij@linaro.org> Reviewed-by: Cédric Le Goater <clg@kaod.org> Signed-off-by: Pavel Machek <pavel@ucw.cz> |
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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.
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.