On Mon, Nov 14, 2016 at 7:53 PM, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote: > It's about figuring out the setting of a "GPIO" that can't be changed from > software. > > Devices sometimes, instead of a configuration bus like I2C or SPI, use > simple input pins, that can either be set to high or low, to allow software > the state of the device. The GPIO API is typically used to configure these pins. > > This works fine as long as the pin is connected to a GPIO. But sometimes the > system designer decides that a settings does not need to be configurable, in > this case the pin will be tied to logic low or high directly on the PCB > without any GPIO controller being involved. > > Sometimes a driver wants to know how the pin is wired up so it can report to > userspace this part runs in the following mode and the mode can't be > changed. In a sense it is like a reverse GPIO hog. > > Considering that this is a common usecase the question was how this can be > implemented in a driver independent way to avoid code duplication and > slightly different variations of what is effectively the same DT/ACPI binding. > > E.g. lets say for a configurable pin you use > > range-gpio = <&gpio ...>; > > and for a static pin > > range-gpio-fixed = <1>; > > Or something similar. Aha I understand. Usually I feel we need not shoehorn stuff into GPIO because it is convenient, it might be best to leave the GPIO optional and if it is not there, look for a custom attribute that represents the "hogging" to 0/1. I think trying to extend GPIO bindings to cover it is overgeneralization, instead go for a local binding for this kind of devices. But mainly it is a question to the DT bindings maintainers. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
