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=-4.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 8186FC4727E for ; Wed, 30 Sep 2020 09:52:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E96F2075F for ; Wed, 30 Sep 2020 09:52:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601459522; bh=sc+AQYG1RYfRu1GfD0zZ2JdLkx36ONLoOSKxzRGYl+U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=jqAzf2Kg0Klwc9o/yB3PPhblGwQppMD1+2V2blBArJuLzRhz2CxPgtKA8mLWUuHF3 WBYKVk9z9PrSCLi8A8Ht8+Ttg48jNUqONxahTjxi7yM2Spt/YxHsaryloDsouX9tAi AZgQwtciyRonzUeBJT/wkI7qobyYZo0f4sBROiB4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725823AbgI3JwC (ORCPT ); Wed, 30 Sep 2020 05:52:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:47914 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725779AbgI3JwB (ORCPT ); Wed, 30 Sep 2020 05:52:01 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9B0732074A; Wed, 30 Sep 2020 09:52:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601459521; bh=sc+AQYG1RYfRu1GfD0zZ2JdLkx36ONLoOSKxzRGYl+U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nHevHf2ZIyWvAhviCcNO55bnfgd3PWWLS4IM5QDsNQptwb5yVfs3UBqH94RksgG/M ejK2dCh9w93TmYYKlpIiZuoHr4ZkAI19oHVti/kLS+zEV0lzmvEQnjtQqWKqJARHtE Y0zqD9CWTpDxGNJKY/mtjFih/iK/31Std6MpAGjE= Date: Wed, 30 Sep 2020 11:52:04 +0200 From: Greg Kroah-Hartman To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Cc: Lars Poeschel , Thierry Reding , Lee Jones , "open list:PWM SUBSYSTEM" , open list Subject: Re: [PATCH] pwm: sysfs: Set class on pwm devices Message-ID: <20200930095204.GA1585476@kroah.com> References: <20200929121953.2817843-1-poeschel@lemonage.de> <20200930065726.fjcsm4pfh65medgl@pengutronix.de> <20200930092056.maz5biy2ugr6yc3p@lem-wkst-02.lemonage> <20200930094146.73s3qzvf5ekjeavc@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200930094146.73s3qzvf5ekjeavc@pengutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org On Wed, Sep 30, 2020 at 11:41:46AM +0200, Uwe Kleine-König wrote: > Hello, > > I added Greg Kroah-Hartman who I discussed this with via irc a bit to > Cc:. > > On Wed, Sep 30, 2020 at 11:20:56AM +0200, Lars Poeschel wrote: > > thank you for your review! > > > > On Wed, Sep 30, 2020 at 08:57:26AM +0200, Uwe Kleine-König wrote: > > > On Tue, Sep 29, 2020 at 02:19:53PM +0200, poeschel@lemonage.de wrote: > > > > From: Lars Poeschel > > > > > > > > This adds a class to exported pwm devices. > > > > Exporting a pwm through sysfs did not yield udev events. The > > > > > > I wonder what is your use-case here. This for sure also has a place to > > > be mentioned in the commit log. I suspect there is a better way to > > > accomplish you way. > > > > Use-case is to be able to use a pwm from a non-root userspace process. > > I use udev rules to adjust permissions. > > Hmm, how do you trigger the export? Without being aware of all the > details in the sysfs code I would expect that the exported stuff is > available instantly once the write used to export the PWM is completed. > So changing the permissions can be done directly after triggering the > export in the same process. It looks like userspace wants to see when a pwmX device shows up, right? And it's not because those devices do not belong to any class or bus, so they are just "floating" out there (they might show up under /sys/bus/virtual, if you set things up right, which I don't think is happening here...) So yes, you need to create a class, or assign this to a bus, which is fine, but it looks like no one is doing that. Don't create new classes dynamically, but rather, just assign this to the existing pwm class. What's wrong with that? I saw an older patch that did that, what did that break? thanks, greg k-h