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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_2 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 AA865C433E0 for ; Wed, 8 Jul 2020 14:56:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83E0220720 for ; Wed, 8 Jul 2020 14:56:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=nic.cz header.i=@nic.cz header.b="h7o61047" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729689AbgGHO4W (ORCPT ); Wed, 8 Jul 2020 10:56:22 -0400 Received: from mail.nic.cz ([217.31.204.67]:55036 "EHLO mail.nic.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729625AbgGHO4W (ORCPT ); Wed, 8 Jul 2020 10:56:22 -0400 Received: from dellmb (unknown [IPv6:2001:1488:fffe:6:cac7:3539:7f1f:463]) by mail.nic.cz (Postfix) with ESMTPSA id 1682C13F695; Wed, 8 Jul 2020 16:56:20 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=nic.cz; s=default; t=1594220180; bh=giCnF4goR1Cb9ewxi13p5MAhs9JmU9oUD5KGQ3U//Yk=; h=Date:From:To; b=h7o61047UMvbF+/3ewFKec5zBgGUDjUmm8FTMSMt+fBuXTZk7j2mC+GvoZZfqwwF2 vQvnLMi5USDjMNzjwJVVHqoo+KCBdks8elMqxfchRFGuX9iIH0j9vgxzfXh3FzlLK9 YMSHS0y3ZcsjoqBIxSDGlaNfmgTUf80LXMLzo5dU= Date: Wed, 8 Jul 2020 16:56:19 +0200 From: Marek =?ISO-8859-1?Q?Beh=FAn?= To: Pavel Machek Cc: Ondrej Jirman , linux-kernel@vger.kernel.org, Jacek Anaszewski , Dan Murphy , "open list:LED SUBSYSTEM" Subject: Re: [PATCH RFC] leds: Add support for per-LED device triggers Message-ID: <20200708165619.0321d3db@dellmb> In-Reply-To: <20200704125900.GA20503@amd> References: <20200702144712.1994685-1-megous@megous.com> <20200703120602.457cff1a@dellmb.labs.office.nic.cz> <20200704125900.GA20503@amd> X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Virus-Scanned: clamav-milter 0.102.2 at mail X-Virus-Status: Clean Sender: linux-leds-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-leds@vger.kernel.org On Sat, 4 Jul 2020 14:59:00 +0200 Pavel Machek wrote: > Hi! > > > Some criticism to this approach to HW triggers: > > - every hw trigger for each LED has to be registered via current > > trigger API. This will grow code size and memory footprint once > > this API is widely used > > - one HW trigger can only master one LED device (via private_led > > member). So if I have, for example an ethernet switch with 8 > > ports, and each port has 2 LEDs, and each LED has 10 possible HW > > triggering mechanisms, with your proposed API one would need to > > register 8*2*10 = 160 triggers > > Well, code is simple, and so far I have seen 2 HW triggering > mechanisms, not 10. Maybe we should have a function to regiter a hw > trigger for a LED, so that internal implementation can be changed > more easily. > > Ondrej: You already have code using this, right? Can we get an > example? > > > I too have been thinking about an API for HW LED triggers, and I > > tinkered with it a little. Some time ago I sent some emails, with > > subjects: > > "RFC: LED hw triggering API" > > "about my trigger-sources work" > > Perhaps it is time to send them one more time, so Ondrej can say if it > works for him/looks okay for him? > > > My current thoughts about how HW LED triggers could work nicely is > > as such: > > - these members (maybe with different names) shall be added to > > struct led_classdev: > > available_hw_triggers() > > - shall return a NULL terminated list of HW trigger names > > available for this LED > > set_hw_trigger() > > - sets HW trigger for this LED. The LED triggering API shall > > call this method after previous LED trigger is unset. If > > called with NULL parameter, unsets HW trigger > > current_hw_trigger > > - name of the currently set HW LED trigger for this LED > > - the driver registering the LED cdev informs abouth the LED being > > capable of HW triggering - members available_hw_triggers and > > set_hw_trigger must be set > > - SW LED trigger and HW LED trigger are mutualy exclusive on one > > LED > > - the trigger file in sysfs (/sys/class/leds/LED/trigger) shall > > first list the available SW triggers, and then available hw > > triggers for this LED, prefixed with "hw:" > > When written, if the written trigger name starts with "hw:", > > instead of setting SW trigger, a HW trigger is set via > > set_hw_trigger() method > > This does not sound bad, either. > > Best regards, > Pavel Hi Pavel I shall try to implement this and send a proposal within 2 weeks. Marek