On 14 November 2016 18:53:28 GMT+00:00, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote: >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? Probably didn't help clarity that I described it as an input pin whereas it's kind of like having an output pin whose state you can't change... >>> 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 -- Sent from my Android device with K-9 Mail. Please excuse my brevity. -- 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
