On Wed, Oct 29, 2025 at 12:20 PM Bartosz Golaszewski <[email protected]> wrote: > > Problem statement: GPIOs are implemented as a strictly exclusive > resource in the kernel but there are lots of platforms on which single > pin is shared by multiple devices which don't communicate so need some > way of properly sharing access to a GPIO. What we have now is the > GPIOD_FLAGS_BIT_NONEXCLUSIVE flag which was introduced as a hack and > doesn't do any locking or arbitration of access - it literally just hand > the same GPIO descriptor to all interested users. > > The proposed solution is composed of three major parts: the high-level, > shared GPIO proxy driver that arbitrates access to the shared pin and > exposes a regular GPIO chip interface to consumers, a low-level shared > GPIOLIB module that scans firmware nodes and creates auxiliary devices > that attach to the proxy driver and finally a set of core GPIOLIB > changes that plug the former into the GPIO lookup path. > > The changes are implemented in a way that allows to seamlessly compile > out any code related to sharing GPIOs for systems that don't need it. > > The practical use-case for this are the powerdown GPIOs shared by > speakers on Qualcomm db845c platform, however I have also extensively > tested it using gpio-virtuser on arm64 qemu with various DT > configurations. > > I'm Cc'ing some people that may help with reviewing/be interested in > this: OF maintainers (because the main target are OF systems initially), > Mark Brown because most users of GPIOD_FLAGS_BIT_NONEXCLUSIVE live > in audio or regulator drivers and one of the goals of this series is > dropping the hand-crafted GPIO enable counting via struct > regulator_enable_gpio in regulator core), Andy and Mika because I'd like > to also cover ACPI (even though I don't know about any ACPI platform that > would need this at the moment, I think it makes sense to make the > solution complete), Dmitry (same thing but for software nodes), Mani > (because you have a somewhat related use-case for the PERST# signal and > I'd like to hear your input on whether this is something you can use or > maybe it needs a separate, implicit gpio-perst driver similar to what > Krzysztof did for reset-gpios) and Greg (because I mentioned this to you > last week in person and I also use the auxiliary bus for the proxy > devices). > > Merging strategy: patches 1-6 should go through the GPIO tree and then > ARM-SoC, ASoC and regulator trees can pull these changes from an > immutable branch and apply the remaining patches. >
Can I get some Reviewed-bys under the GPIO patches if there are no other open issues? I would like for this to start making its way upstream if there are no strong objections to the concept. After a release or two, I'd like to start enabling it on more platforms. Bart
