On Thu, Aug 28, 2025 at 7:00 PM Bartosz Golaszewski <brgl@xxxxxxxx> wrote: > > Problem: when pinctrl core binds pins to a consumer device and the > pinmux ops of the underlying driver are marked as strict, the pin in > question can no longer be requested as a GPIO using the GPIO descriptor > API. It will result in the following error: > > [ 5.095688] sc8280xp-tlmm f100000.pinctrl: pin GPIO_25 already requested by regulator-edp-3p3; cannot claim for f100000.pinctrl:570 > [ 5.107822] sc8280xp-tlmm f100000.pinctrl: error -EINVAL: pin-25 (f100000.pinctrl:570) > > This typically makes sense except when the pins are muxed to a function > that actually says "GPIO". Of course, the function name is just a string > so it has no meaning to the pinctrl subsystem. > > We have many Qualcomm SoCs (and I can imagine it's a common pattern in > other platforms as well) where we mux a pin to "gpio" function using the > `pinctrl-X` property in order to configure bias or drive-strength and > then access it using the gpiod API. This makes it impossible to mark the > pin controller module as "strict". > > This series proposes to introduce a concept of a sub-category of > pinfunctions: GPIO functions where the above is not true and the pin > muxed as a GPIO can still be accessed via the GPIO consumer API even for > strict pinmuxers. > > To that end: we first clean up the drivers that use struct function_desc > and make them use the smaller struct pinfunction instead - which is the > correct structure for drivers to describe their pin functions with. We > also rework pinmux core to not duplicate memory used to store the > pinfunctions unless they're allocated dynamically. > > First: provide the kmemdup_const() helper which only duplicates memory > if it's not in the .rodata section. Then rework all pinctrl drivers that > instantiate objects of type struct function_desc as they should only be > created by pinmux core. Next constify the return value of the accessor > used to expose these structures to users and finally convert the > pinfunction object within struct function_desc to a pointer and use > kmemdup_const() to assign it. With this done proceed to add > infrastructure for the GPIO pin function category and use it in Qualcomm > drivers. At the very end: make the Qualcomm pinmuxer strict. Note mainly for Linus and Bart: I agree with the patches 1..11, but starting from 12 needs more discussion. That said, I hope Linus can apply the first 11 ones to make it easier to continue with the rest. -- With Best Regards, Andy Shevchenko
