Hi Krzysztof, something is odd with the addresses on this patch, because neither GPIO maintainer is on CC nor linux-gpio@vger, and it's such a GPIO-related patch. We only saw it through side effects making <linux/gpio/driver.h> optional, as required by this patch. Please also CC Geert Uytterhoeven, the author of the GPIO aggregator. i.e. this: > 2. !GPIOLIB stub: > https://lore.kernel.org/all/20240125081601.118051-3-krzysztof.kozlowski@xxxxxxxxxx/ On Mon, Jan 29, 2024 at 12:53 PM Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> wrote: > Devices sharing a reset GPIO could use the reset framework for > coordinated handling of that shared GPIO line. We have several cases of > such needs, at least for Devicetree-based platforms. > > If Devicetree-based device requests a reset line, while "resets" > Devicetree property is missing but there is a "reset-gpios" one, > instantiate a new "reset-gpio" platform device which will handle such > reset line. This allows seamless handling of such shared reset-gpios > without need of changing Devicetree binding [1]. > > To avoid creating multiple "reset-gpio" platform devices, store the > Devicetree "reset-gpios" GPIO specifiers used for new devices on a > linked list. Later such Devicetree GPIO specifier (phandle to GPIO > controller, GPIO number and GPIO flags) is used to check if reset > controller for given GPIO was already registered. > > If two devices have conflicting "reset-gpios" property, e.g. with > different ACTIVE_xxx flags, this would allow to spawn two separate > "reset-gpio" devices, where the second would fail probing on busy GPIO > request. > > Link: https://lore.kernel.org/all/YXi5CUCEi7YmNxXM@xxxxxxxxxxxxxxxxxx/ [1] > Cc: Bartosz Golaszewski <brgl@xxxxxxxx> > Cc: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx> > Cc: Sean Anderson <sean.anderson@xxxxxxxx> > Reviewed-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> > Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> (...) In my naive view, this implements the following: reset -> virtual "gpio" -> many physical gpios[0..n] So if there was already a way in the kernel to map one GPIO to many GPIOs, the framework could just use that with a simple single GPIO? See the bindings in: Documentation/devicetree/bindings/gpio/gpio-delay.yaml This is handled by drivers/gpio/gpio-aggregator.c. This supports a 1-to-1 map: one GPIO in, one GPIO out, same offset. So if that is extended to support 1-to-many, this problem is solved. Proposed solution: add a single boolean property such as aggregate-all-gpios; to the gpio-delay node, making it provide one single gpio at offset 0 on the consumer side, and refuse any more consumers. This will also solve the problem with induced delays on some GPIO lines as I can see was discussed in the bindings, the gpio aggregator already supports that, but it would work fine with a delay being zero as well. This avoids all the hackery with driver stubs etc as well. Yours, Linus Walleij
