Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1947728AbdD1KKF (ORCPT ); Fri, 28 Apr 2017 06:10:05 -0400 Received: from mail-io0-f193.google.com ([209.85.223.193]:34712 "EHLO mail-io0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S968680AbdD1KJ4 (ORCPT ); Fri, 28 Apr 2017 06:09:56 -0400 MIME-Version: 1.0 In-Reply-To: References: <1493281194-5200-1-git-send-email-jacopo+renesas@jmondi.org> <1493281194-5200-2-git-send-email-jacopo+renesas@jmondi.org> From: Geert Uytterhoeven Date: Fri, 28 Apr 2017 12:09:49 +0200 X-Google-Sender-Auth: ui-9EOY-Qe_oZ73Z6TBO9klw0AA Message-ID: Subject: Re: [PATCH v5 01/10] pinctrl: generic: Add bi-directional and output-enable To: Linus Walleij Cc: Andy Shevchenko , Jacopo Mondi , Geert Uytterhoeven , Laurent Pinchart , Chris Brandt , Rob Herring , Mark Rutland , Russell King - ARM Linux , Linux-Renesas , "linux-gpio@vger.kernel.org" , devicetree , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1907 Lines: 53 Hi Linus, On Fri, Apr 28, 2017 at 10:32 AM, Linus Walleij wrote: > On Thu, Apr 27, 2017 at 4:56 PM, Andy Shevchenko > wrote: >> On Thu, Apr 27, 2017 at 11:19 AM, Jacopo Mondi >> wrote: >>> Add bi-directional and output-enable pin configuration properties. >>> >>> bi-directional allows to specify when a pin shall operate in input and >>> output mode at the same time. This is particularly useful in platforms >>> where input and output buffers have to be manually enabled. >>> >>> output-enable is just syntactic sugar to specify that a pin shall >>> operate in output mode, ignoring the provided argument. >>> This pairs with input-enable pin configuration option. >> >> For me it looks like you are trying to alias open-drain + bias or >> alike. Don't actually see the benefit of it. > > Andy is bringing up a valid point. And I remember asking about > this before. > > What does "bi-directional" really mean, electrically speaking? > > Does is just mean open drain and/or open source actually? > (See Documentation/gpio/driver.txt for an explanation of > how open drain/source works.) > > When you set an output without setting a value, what happens > electrically? > > Isn't this bias-high-impedance / High-Z? > > Hopefully you can find the answer from Renesas hardware dept. > > You can certainly call it whatever the datasheet calls it > in your driver #defines but for the DT bindings we would > ideally have the physical world things. FWIW, you have already applied v4. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds