Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934539AbaJ2Qu2 (ORCPT ); Wed, 29 Oct 2014 12:50:28 -0400 Received: from mail-wi0-f174.google.com ([209.85.212.174]:43407 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934103AbaJ2QuY convert rfc822-to-8bit (ORCPT ); Wed, 29 Oct 2014 12:50:24 -0400 Subject: Re: [RFC Patch] gpio: add GPIO hogging mechanism Mime-Version: 1.0 (Mac OS X Mail 8.0 \(1990.1\)) Content-Type: text/plain; charset=utf-8 From: Pantelis Antoniou In-Reply-To: <20141029163445.GB29965@ti.com> Date: Wed, 29 Oct 2014 18:42:48 +0200 Cc: Linus Walleij , linux-gpio@vger.kernel.org, linux-kernel , devicetree@vger.kernel.org Content-Transfer-Encoding: 8BIT Message-Id: <2BA5D07E-B5EF-49E1-BFD2-310A6C5F3FE4@gmail.com> References: <1413922198-29373-1-git-send-email-bparrot@ti.com> <3D00ADB3-00B3-40A8-8263-444BCADDAC33@gmail.com> <20141029163445.GB29965@ti.com> To: Benoit Parrot X-Mailer: Apple Mail (2.1990.1) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Benoit, > On Oct 29, 2014, at 18:34 , Benoit Parrot wrote: > > Pantelis, > > Thanks for the feedback. > > Pantelis Antoniou wrote on Wed [2014-Oct-29 10:53:44 +0200]: >> Hi Benoit, >> >>> On Oct 21, 2014, at 23:09 , Benoit Parrot wrote: >>> >>> Based on Boris Brezillion work this is a reworked patch >>> of his initial GPIO hogging mechanism. >>> This patch provides a way to initally configure specific GPIO >>> when the gpio controller is probe. >>> >>> The actual DT scanning to collect the GPIO specific data is performed >>> as part of the gpiochip_add(). >>> >>> The purpose of this is to allows specific GPIOs to be configured >>> without any driver specific code. >>> This particularly usueful because board design are getting >>> increassingly complex and given SoC pins can now have upward >>> of 10 mux values a lot of connections are now dependent on >>> external IO muxes to switch various modes and combination. >>> >>> Specific drivers should not necessarily need to be aware of >>> what accounts to a specific board implementation. This board level >>> "description" should be best kept as part of the dts file. >>> >> >> This look like it’s going to the right direction. I have a few general >> comments at first. >> >> 1) It relies on dubious DT binding of having sub-nodes of the >> gpio device implicitly defining hogs. > > I think in this instance the nodes are explicitly defining hogs. > Please clarify. What would you like to see here? >> Any subnodes are implicitly taken as hog definitions. This is not right because gpio controllers might have subnodes that they use for another purpose. >> 2) There is no way for having hogs inserted dynamically as far as I can tell, and >> no way to remove a hog either. > > The original patch was allowing that but, Linus's review comment suggested this feature be > part of the gpio-controller's gpiochip_add() hook only. > If it’s not possible to remove a hog, then it’s no good for my use case in which the gpios get exported and then removed. >> >> 3) I’m not very fond of having this being part of the gpio controller. This >> configuration conceptually has little to do with the gpio controller per se, >> it is more of a board specific thing. Why not come up with a gpio-hog driver that >> references GPIOs? That way with a single gpio-hog driver instance you could setup >> all the GPIO-hogging configuration for all GPIOs on the board, even one that >> lie on different GPIO controllers. > > Again this follows Linus's review comment. > I agree that it prevent a centralize spot where all hog would be defined but it has the advantages of not relying on PROBE_DEFER. > I mean since all "gpio-hogs" would be defined in a single board dts file it would not be that hard to figure out the big picture anyways. > There won’t be a single board dts file if you’re using things like overlays. >> >> >>> Signed-off-by: Benoit Parrot >>> --- >>> Documentation/devicetree/bindings/gpio/gpio.txt | 33 +++++++++ >>> drivers/gpio/gpiolib-of.c | 99 +++++++++++++++++++++++++ >>> drivers/gpio/gpiolib.c | 81 ++++++++++++++++++++ >>> include/linux/of_gpio.h | 11 +++ >>> 4 files changed, 224 insertions(+) >>> >> >> Regards >> >> — Pantelis >> > > Regards, > Benoit Regards — Pantelis -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/