From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH v5 2/6] leds: triggers: Add a keyboard backlight trigger Date: Fri, 25 Nov 2016 21:40:45 +0100 Message-ID: <20161125204045.GA28036@amd> References: <5238be1f-d669-07e6-c796-5bc0126cb456@gmail.com> <201611242245.00217@pali> <20161125100140.GC4062@amd> <20161125110557.GA13204@amd> <2367b9a7-68f7-2038-0d3a-a9561055b4f6@samsung.com> <20161125144859.GA20139@amd> <9844f7b3-c3e8-99d8-61b6-1550b1b8ab7e@samsung.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="1yeeQ81UyVL57Vl7" Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:43867 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932863AbcKYUku (ORCPT ); Fri, 25 Nov 2016 15:40:50 -0500 Content-Disposition: inline In-Reply-To: <9844f7b3-c3e8-99d8-61b6-1550b1b8ab7e@samsung.com> Sender: linux-leds-owner@vger.kernel.org List-Id: linux-leds@vger.kernel.org To: Jacek Anaszewski Cc: Pali =?iso-8859-1?Q?Roh=E1r?= , Jacek Anaszewski , gdg@zplane.com, Hans de Goede , Darren Hart , Matthew Garrett , Henrique de Moraes Holschuh , Richard Purdie , ibm-acpi-devel@lists.sourceforge.net, platform-driver-x86@vger.kernel.org, linux-leds@vger.kernel.org --1yeeQ81UyVL57Vl7 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > >>Triggers are not limited to periodic blinking or reporting cpu > >>activity. There is also oneshot trigger that can be used e.g. when > >>user touches the screen, as Pali mentioned. > > > >Using oneshot trigger for this would be pretty strange. >=20 > It was only an example to mention other than periodic triggers. > You could have a trigger that just turns the LED permanently on > after user touches the screen. Well.. triggers kind of assume they control the LED. They were not prepared to deal with hardware changing the brightness behind their back. > >Notice that in > >some cases (thinkpad battery led, for example) we either have firmware > >controls the LED (but then software can't control it) or we have > >software controlling the LED (but then we don't know what firmware > >would put there). Maybe keyboard backlight can be controlled > >"simultaneously" by both software and firmware, but there are > >certainly LEDs that can't handle that, and IMO it would be nice to > >have same interface. > > > >>>Well.. actually... I think this is a little bit over complex and > >>>probably unneccessary. I'd let Hans implement whatever he thinks is > >>>easiest. > >> > >>I'd say this is the trigger approach which is a bit convoluted. > > > >In my eyes trigger approach is neccessary at least for some hardware, > >and things it pretty clear: trigger on =3D=3D LED changes without > >userspace involvement. trigger off =3D=3D userspace controls the LED. >=20 > It is likely that it would break many existing users. Can you elaborate on that? I just tried with leds on thinkpad root@duo:/sys/class/leds/tpacpi::power# echo 1 > brightness root@duo:/sys/class/leds/tpacpi::power# echo 0 > brightness root@duo:/sys/class/leds/tpacpi::power# cat trigger [none] bluetooth-power kbd-scrollock kbd-numlock kbd-capslock kbd-kanalock kbd-shiftlock kbd-altgrlock kbd-ctrllock kbd-altlock kbd-shiftllock kbd-shiftrlock kbd-ctrlllock kbd-ctrlrlock AC-online BAT0-charging-or-full BAT0-charging BAT0-full BAT0-charging-blink-full-solid rfkill0 phy0rx phy0tx phy0assoc phy0radio phy0tpt mmc0 timer pattern rfkill1 hci0-power rfkill74 heartbeat root@duo:/sys/class/leds/tpacpi::power# I can control the LED from userspace, but then there's no way to put the LED back to firmware control. That's just broken. Do you have a proposal how to handle that? > >So I'd do the trigger here. It is same way we can handle LEDs on > >thinkpad. Yes, it means you won't be able to do oneshot trigger on > >backlight. I don't think that's a huge problem. >=20 > There have been voices in this discussion claiming the opposite. :-) Well, lets ignore those voices until the voices understand the current design :-). Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --1yeeQ81UyVL57Vl7 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlg4oc0ACgkQMOfwapXb+vJjwQCeJvKUdvBkhGya4cVzuQPhNBFg y4QAn1rNmUSp5eMRTxTdQmcuFiEeTw8n =7Eci -----END PGP SIGNATURE----- --1yeeQ81UyVL57Vl7--