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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 86345C48BD1 for ; Wed, 9 Jun 2021 14:16:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5C91961351 for ; Wed, 9 Jun 2021 14:16:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234813AbhFIOSV (ORCPT ); Wed, 9 Jun 2021 10:18:21 -0400 Received: from netrider.rowland.org ([192.131.102.5]:59497 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S233850AbhFIOST (ORCPT ); Wed, 9 Jun 2021 10:18:19 -0400 Received: (qmail 1843599 invoked by uid 1000); 9 Jun 2021 10:16:23 -0400 Date: Wed, 9 Jun 2021 10:16:23 -0400 From: Alan Stern To: Ulf Hansson Cc: "Rafael J . Wysocki" , linux-pm@vger.kernel.org, Saravana Kannan , Adrian Hunter , Tony Lindgren , Kevin Hilman , Geert Uytterhoeven , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 3/3] PM: runtime: Clarify documentation when callbacks are unassigned Message-ID: <20210609141623.GA1842836@rowland.harvard.edu> References: <20210609100610.97830-1-ulf.hansson@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210609100610.97830-1-ulf.hansson@linaro.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 09, 2021 at 12:06:10PM +0200, Ulf Hansson wrote: > Recent changes to the PM core allows ->runtime_suspend|resume callbacks to > be unassigned. > > In the earlier behaviour the PM core would return -ENOSYS, when trying to > runtime resume a device, for example. Let's update the documentation to > clarify this. > > Signed-off-by: Ulf Hansson > --- > > Changes in v4: > - This time, really, fix spelling and further clarified the behaviour, > according to comments from Alan. > > --- > Documentation/power/runtime_pm.rst | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst > index 18ae21bf7f92..8a0a43811e3a 100644 > --- a/Documentation/power/runtime_pm.rst > +++ b/Documentation/power/runtime_pm.rst > @@ -827,6 +827,15 @@ or driver about runtime power changes. Instead, the driver for the device's > parent must take responsibility for telling the device's driver when the > parent's power state changes. > > +Note that, in some cases it may not be desirable for subsystems/drivers to call > +pm_runtime_no_callbacks() for their devices. This could be because a subset of > +the runtime PM callbacks needs to be implemented, a platform dependent PM > +domain could get attached to the device or that the device is power managed > +through a supplier device link. For these reasons and to avoid boilerplate code > +in subsystems/drivers, the PM core allows runtime PM callbacks to be > +unassigned. More precisely, if a callback pointer is NULL, the PM core will act > +as though there was a callback and it returned 0. > + > 9. Autosuspend, or automatically-delayed suspends > ================================================= Acked-by: Alan Stern I don't know what happened before. Maybe the terminal window got resized without me noticing, so the lines looked too long when they actually weren't. Alan Stern