From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: [PATCH v5 2/6] leds: triggers: Add a keyboard backlight trigger Date: Thu, 24 Nov 2016 17:21:19 +0100 Message-ID: References: <05766b18-026a-2af3-def8-9289ddb55234@samsung.com> <4fcc36c6-498b-0ce7-a7c8-28c214ccef88@redhat.com> <20161122145825.GS13735@pali> <6e8c3884-fec1-461a-e9b8-2020176ada93@samsung.com> <20161124091525.GG13735@pali> <20161124142647.GJ13735@pali> <50225a88-b928-c61b-bf6f-6c85fb6a9082@samsung.com> <20161124153651.GL13735@pali> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-reply-to: <20161124153651.GL13735@pali> Sender: linux-leds-owner@vger.kernel.org To: =?UTF-8?Q?Pali_Roh=c3=a1r?= Cc: gdg@zplane.com, Hans de Goede , Pavel Machek , Jacek Anaszewski , 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 List-Id: platform-driver-x86.vger.kernel.org On 11/24/2016 04:36 PM, Pali Rohár wrote: > On Thursday 24 November 2016 16:32:06 Jacek Anaszewski wrote: >> Since it has been reported that POLLPRI notifications on brightness >> file can lead to increased power consumption, and having my above >> statement I don't think that it is a good idea to use brightness >> file for this. > > How is brightness file different from others that it cannot issue > POLLPRI notification? > > I understood that problem is there in case that LED level is changed too > many times per second (like by CPU trigger). > > If this is not that problem can you describe real issue, why we cannot > use POLLPRI for brightness file? It would be inconsistent not to notify all brightness changes on brightness file. We should notify all of them or none. >>> Yes, how triggers interact with brightness file, what happen when you >>> write 0 on active trigger, >> >> There is already a patch in linux-next adding the following: >> >> >> + Writing 0 to this file clears active trigger. >> + >> + Writing non-zero to this file while trigger is active changes the >> + top brightness trigger is going to use. >> + > > Great! > >>> what happen when you read brightness file >>> with active trigger / without trigger. >>> >> >> Yes, this needs to be covered too. > -- Best regards, Jacek Anaszewski