On 11/14/2016 05:58 PM, Linus Walleij wrote: > On Sat, Nov 12, 2016 at 3:24 PM, Jonathan Cameron <jic23@xxxxxxxxxx> wrote: > >> Is it just me who thought, we need a fixed GPI like a fixed regulator? >> Would allow this sort of fixed wiring to be simply defined. >> >> Linus, worth exploring? > > So if fixed regulator is for a voltage provider, this would be > pretty much the inverse: deciding for a voltage range by switching > a GPIO. 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. -- 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
