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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 98836C83004 for ; Wed, 29 Apr 2020 12:38:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 75E4B2072A for ; Wed, 29 Apr 2020 12:38:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="fMMGd7cu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726815AbgD2Mi2 (ORCPT ); Wed, 29 Apr 2020 08:38:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43824 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726741AbgD2Mi1 (ORCPT ); Wed, 29 Apr 2020 08:38:27 -0400 Received: from mail-lj1-x244.google.com (mail-lj1-x244.google.com [IPv6:2a00:1450:4864:20::244]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 21A95C03C1AE for ; Wed, 29 Apr 2020 05:38:27 -0700 (PDT) Received: by mail-lj1-x244.google.com with SMTP id u15so2449793ljd.3 for ; Wed, 29 Apr 2020 05:38:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=yiklenLhNOV+HKXdiZuFGpxcMEuzoxvnXmW3/CZQYZs=; b=fMMGd7cuYi00xYIotGRhY6Dnx7VYaht0u0LQuHp4fzcCDF9cBBdPfE+f8GXRMwcza0 cLuwR336ZmgamL7yC676FL5jlkc5Yz1B+1TS4yVNxDprMVCznLRjQdK1bX816iSRAWxd vCvTGXv3tDcjKsafsNJiLTH2Z/TFLyyqrthbVHJxlAAPpgxWK/RlNhJUDw9OLXdE0smj kKtaF64FI9ricj+z5+PMpVi/HcrBHhYWQc6Hw715u3+ZxxFmFXuhjNN83YcHp7lHpcvi 20w3ODJEGsB2yuhAXLnYyJ0Snyklwuq81N5iNcKJMXc7Xiiwx6j9alt/6cDGQgxFy6hX VDvw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=yiklenLhNOV+HKXdiZuFGpxcMEuzoxvnXmW3/CZQYZs=; b=nTYV3AK3SXLXweOXFWuTv5AQu5Wxbyoc5x3pL6f+88hU91VrcHDkGC3AzEk8111PuG KXmsHmbSKuEwyoYryPcCkUJHh6xq0kHarUvxdJ/7jpiVCV6tY1KkxMbNjhXhFGVPZTNV ywvrR1kqzcVY6XaDLAXj9GrkFY4lDNwQWAd3LyL70NvvOfEGD1NiIXOwIpUUOD4S7O9n /+r8MdQ5Aj1qPRjar404pGDZUy7RW87t48r0q8mSTtm0Dwv7kBaGnwtKoL1Bv+Uz+D3G pZpRV197/K9CL8fxWRJQSzveWs0ZPZEyQ6iVjiDuPer5q0yJlwz8yP2bDPyAkLHZm38E 6bUQ== X-Gm-Message-State: AGi0PubXlhqtfERy5unahsePLsLvE03tFRssdYrOXv+E4QKczDXVr09l +RiBa08YezQBujmo8sB0xIHe1amzn++U9zj7J83UbA== X-Google-Smtp-Source: APiQypJSjoxKbAKfAOvydqwj3C8SjC23BV+vHuypyRaJJ1bGKEYT/DUGGPAuboZMKwIe81ZCOER6hgFyOq7nxIlRwZg= X-Received: by 2002:a05:651c:1058:: with SMTP id x24mr21640311ljm.39.1588163905575; Wed, 29 Apr 2020 05:38:25 -0700 (PDT) MIME-Version: 1.0 References: <20200419001858.105281-1-hector.bujanda@digi.com> In-Reply-To: From: Linus Walleij Date: Wed, 29 Apr 2020 14:38:13 +0200 Message-ID: Subject: Re: [PATCH] gpiolib: add GPIO_SET_DEBOUNCE_IOCTL To: Bartosz Golaszewski Cc: Hector Bujanda , "open list:GPIO SUBSYSTEM" , Linux Kernel Mailing List , Kent Gibson Content-Type: text/plain; charset="UTF-8" Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org On Wed, Apr 29, 2020 at 2:06 PM Bartosz Golaszewski wrote: > I understand the need to set debounce time to make line events > reliable. As I see it: there'll be a couple steps to add this. I think there is a serious user-facing problem here though, because not all GPIO controllers supports debounce, so the call may return "nope" (error code). I think that is unavoidable with things like pull-up/down or drive strength, but for debounce I think we could do better. drivers/input/keyboard/gpio_keys.c contains generic debounce code using kernel timers if the GPIO driver cannot provide debouncing, and I have thought for a long time that it would be nice if we could do this generic, so that we always provide debouncing if requested, even for in-kernel consumers but most certainly for userspace consumers, else userspace will just start to reinvent this too. Yours, Linus Walleij