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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 04C8CC433E0 for ; Sat, 4 Jul 2020 12:59:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E063B20885 for ; Sat, 4 Jul 2020 12:59:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727930AbgGDM7E (ORCPT ); Sat, 4 Jul 2020 08:59:04 -0400 Received: from jabberwock.ucw.cz ([46.255.230.98]:48092 "EHLO jabberwock.ucw.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726738AbgGDM7D (ORCPT ); Sat, 4 Jul 2020 08:59:03 -0400 Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id F22FD1C0BD2; Sat, 4 Jul 2020 14:59:00 +0200 (CEST) Date: Sat, 4 Jul 2020 14:59:00 +0200 From: Pavel Machek To: Marek =?iso-8859-1?Q?Beh=FAn?= 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: <20200704125900.GA20503@amd> References: <20200702144712.1994685-1-megous@megous.com> <20200703120602.457cff1a@dellmb.labs.office.nic.cz> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="fdj2RfSjLxBAspz7" Content-Disposition: inline In-Reply-To: <20200703120602.457cff1a@dellmb.labs.office.nic.cz> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --fdj2RfSjLxBAspz7 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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 > =3D 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 --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --fdj2RfSjLxBAspz7 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAl8AfRQACgkQMOfwapXb+vIOgQCfU+rjWFzjMDjVUO2Au4O9+KFz J+IAoI1wY8zexgdpp1vEpFRsp/FcM/bI =mY9m -----END PGP SIGNATURE----- --fdj2RfSjLxBAspz7--