From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: [PATCH] leds: Allow drivers to update the core, and generate events on changes Date: Tue, 27 Dec 2016 23:57:26 +0100 Message-ID: <3560132e-ac79-b6fa-200c-da9c7ed9d435@gmail.com> References: <20161227191136.4516-1-gabriele.mzt@gmail.com> <20161227200755.GA6345@amd> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Return-path: Received: from mail-wm0-f68.google.com ([74.125.82.68]:36817 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753728AbcL0W6N (ORCPT ); Tue, 27 Dec 2016 17:58:13 -0500 In-Reply-To: <20161227200755.GA6345@amd> Sender: linux-leds-owner@vger.kernel.org List-Id: linux-leds@vger.kernel.org To: Pavel Machek , Gabriele Mazzotta Cc: rpurdie@rpsys.net, linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org Hi Gabriele, Pavel, On 12/27/2016 09:07 PM, Pavel Machek wrote: > Hi! > >> Similarily to commit 325253a6b2de ("backlight: Allow drivers to update >> the core, and generate events on changes"), inform userspace about >> brightness changes and allow drivers to request updates of the >> brightness value. > > First... we had similar patch in tree, and it caused problems, we are > now trying to figure out how to do it properly. > > LED can be updated many times per second, uevent is probably _not_ > good mechanism to achieve that. > > Generating uevent for /sys changes does not make much sense, right? > >> +extern void led_brightness_force_update(struct led_classdev *led_cdev, >> + enum led_brightness_update_reason reason); > > I see this may make some sense, but there are no uses for this in this > patch. > > My preffered solution would be ... for hardware that changes led > brightness itself, introduce a "trigger", so that userspace knows this > led is special, and then provide poll()able /sys fs file interested > parties can read. I've recently submitted for a discussion the idea of "persistent triggers" [0]. Any feedback is very much appreciated. [0] https://www.spinics.net/lists/linux-leds/msg07332.html -- Best regards, Jacek Anaszewski