From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752885AbcKSMcr (ORCPT ); Sat, 19 Nov 2016 07:32:47 -0500 Received: from saturn.retrosnub.co.uk ([178.18.118.26]:46712 "EHLO saturn.retrosnub.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752694AbcKSMcp (ORCPT ); Sat, 19 Nov 2016 07:32:45 -0500 Subject: Re: [PATCH 1/2] staging: iio: ad7606: replace range/range_available with corresponding scale To: Linus Walleij , Lars-Peter Clausen References: <1478846078-22207-1-git-send-email-eraretuya@gmail.com> <1478846078-22207-2-git-send-email-eraretuya@gmail.com> Cc: Eva Rachel Retuya , "linux-iio@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Michael Hennerich , Hartmut Knaack , Peter Meerwald , Greg KH , "devicetree@vger.kernel.org" , Rob Herring , Mark Rutland From: Jonathan Cameron Message-ID: Date: Sat, 19 Nov 2016 12:32:42 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/11/16 23:12, Linus Walleij wrote: > On Mon, Nov 14, 2016 at 7:53 PM, Lars-Peter Clausen 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. That's a reasonable approach, but I'd certainly like to see a generic binding to describe it. It's a pretty common situation. Seems more likely we'll get a device tree maintainer response if we cc them ;) So Mark, Rob and thoughts on this? Thanks, Jonathan > > Yours, > Linus Walleij >