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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 7E50DC433DB for ; Fri, 5 Mar 2021 20:01:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3E9C16509A for ; Fri, 5 Mar 2021 20:01:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229446AbhCEUBE convert rfc822-to-8bit (ORCPT ); Fri, 5 Mar 2021 15:01:04 -0500 Received: from aposti.net ([89.234.176.197]:58206 "EHLO aposti.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229488AbhCEUA4 (ORCPT ); Fri, 5 Mar 2021 15:00:56 -0500 Date: Fri, 05 Mar 2021 20:00:43 +0000 From: Paul Cercueil Subject: Re: [PATCH 3/3] input: gpio-keys: Use hrtimer for software debounce To: Dmitry Torokhov Cc: od@zcrc.me, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Message-Id: <79IIPQ.DQ7JNXZ0OI5Q2@crapouillou.net> In-Reply-To: References: <20210305170111.214782-1-paul@crapouillou.net> <20210305170111.214782-3-paul@crapouillou.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dmitry, Le ven. 5 mars 2021 à 10:35, Dmitry Torokhov a écrit : > Hi Paul, > > On Fri, Mar 05, 2021 at 05:01:11PM +0000, Paul Cercueil wrote: >> -static void gpio_keys_gpio_work_func(struct work_struct *work) >> +static enum hrtimer_restart gpio_keys_debounce_timer(struct >> hrtimer *t) >> { >> - struct gpio_button_data *bdata = >> - container_of(work, struct gpio_button_data, work.work); >> + struct gpio_button_data *bdata = container_of(t, >> + struct gpio_button_data, >> + debounce_timer); >> >> gpio_keys_gpio_report_event(bdata); > > I am not sure how this works. As far as I know, even > HRTIMER_MODE_REL_SOFT do not allow sleeping in the timer handlers, and > gpio_keys_gpio_report_event() use sleeping variant of GPIOD API (and > that is not going to change). Quoting , the "timer callback will be executed in soft irq context", so sleeping should be possible. But I guess in this case I can use HRTIMER_MODE_REL. > It seems to me that if you want to use software debounce in gpio keys > driver you need to set up sufficiently high HZ for your system. Maybe > we > could thrown a warning when we see low debounce delay and low HZ to > alert system developer. This is exactly what we should not do. I certainly don't want to have 250+ timer interrupts per second just so that input events aren't lost, to work around a sucky debounce implementation. Besides, if you consider the hrtimers doc (Documentation/timers/hrtimers.rst), hrtimers really are what should be used here. -Paul