From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6185C5ACD6 for ; Tue, 17 Mar 2020 21:31:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7CAF020754 for ; Tue, 17 Mar 2020 21:31:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726968AbgCQVbM (ORCPT ); Tue, 17 Mar 2020 17:31:12 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:51551 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726494AbgCQVbL (ORCPT ); Tue, 17 Mar 2020 17:31:11 -0400 Received: from pty.hi.pengutronix.de ([2001:67c:670:100:1d::c5]) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1jEJnd-0005vE-6Z; Tue, 17 Mar 2020 22:30:57 +0100 Received: from ukl by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1jEJnc-0004oR-3H; Tue, 17 Mar 2020 22:30:56 +0100 Date: Tue, 17 Mar 2020 22:30:56 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Thierry Reding Cc: Oleksandr Suvorov , devicetree@vger.kernel.org, linux-pwm@vger.kernel.org, Paul Barker , Laurent Pinchart , Marcel Ziswiler , Igor Opaniuk , Philippe Schenker , Rob Herring , linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 2/7] dt-bindings: pwm: document the PWM polarity flag Message-ID: <20200317213056.futfiwn4qgr2njye@pengutronix.de> References: <20200317123231.2843297-1-oleksandr.suvorov@toradex.com> <20200317123231.2843297-3-oleksandr.suvorov@toradex.com> <20200317174344.GB1464607@ulmo> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200317174344.GB1464607@ulmo> User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Thierry, On Tue, Mar 17, 2020 at 06:43:44PM +0100, Thierry Reding wrote: > On Tue, Mar 17, 2020 at 02:32:26PM +0200, Oleksandr Suvorov wrote: > > Add the description of PWM_POLARITY_NORMAL flag. > > > > Signed-off-by: Oleksandr Suvorov > > --- > > > > Documentation/devicetree/bindings/pwm/pwm.txt | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt > > index 084886bd721e..440c6b9a6a4e 100644 > > --- a/Documentation/devicetree/bindings/pwm/pwm.txt > > +++ b/Documentation/devicetree/bindings/pwm/pwm.txt > > @@ -46,6 +46,7 @@ period in nanoseconds. > > Optionally, the pwm-specifier can encode a number of flags (defined in > > ) in a third cell: > > - PWM_POLARITY_INVERTED: invert the PWM signal polarity > > +- PWM_POLARITY_NORMAL: don't invert the PWM signal polarity > > This doesn't make sense. PWM_POLARITY_NORMAL is not part of the DT ABI. "is not part of the DT ABI" is hardly a good reason. If it's sensible to be used, it is sensible to define it. (And as far as I understand it, the term PWM_POLARITY_INVERTED isn't part of the DT ABI either. Only the value 1 has a meaning (for some PWM controlers).) > The third cell of the specifier is a bitmask of flags. > > PWM_POLARITY_NORMAL is an enumeration value that evaluates to 0, so it > makes absolutely no sense as a flag. Using 0 or PWM_POLARITY_NORMAL doesn't have an effect on the compiled device tree, that's true. But having the term PWM_POLARITY_NORMAL (in contrast to a plain 0) in a dts file is useful in my eyes for human readers. > PWM signals are considered to be "normal" by default, so no flag is > necessary to specify that. GPIOs are considered to be active high by default, still there is GPIO_ACTIVE_HIGH (which also evaluates to 0). Also there is IRQ_TYPE_NONE. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |