linux-kernel - Re: [PATCH 1/2] staging: iio: ad7606: replace range/range

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Message-ID: <0F7D932A-3232-4F33-9F46-98789442D721@jic23.retrosnub.co.uk>
Date:   Mon, 14 Nov 2016 22:15:04 +0000
From:   Jonathan Cameron <jic23@...23.retrosnub.co.uk>
To:     Lars-Peter Clausen <lars@...afoo.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Jonathan Cameron <jic23@...nel.org>
CC:     Eva Rachel Retuya <eraretuya@...il.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald <pmeerw@...erw.net>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 1/2] staging: iio: ad7606: replace range/range_available with corresponding scale



On 14 November 2016 18:53:28 GMT+00:00, Lars-Peter Clausen <lars@...afoo.de> wrote:
>On 11/14/2016 05:58 PM, Linus Walleij wrote:
>> On Sat, Nov 12, 2016 at 3:24 PM, Jonathan Cameron <jic23@...nel.org>
>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.
>
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