From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935688AbcIPPcZ (ORCPT ); Fri, 16 Sep 2016 11:32:25 -0400 Received: from vern.gendns.com ([206.190.152.46]:34937 "EHLO vern.gendns.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752827AbcIPPcR (ORCPT ); Fri, 16 Sep 2016 11:32:17 -0400 Subject: Re: [PATCH v3] leds: Introduce userspace leds driver To: Pavel Machek References: <1473439776-15655-1-git-send-email-david@lechnology.com> <80597ded-f4b4-2990-3eae-e72276296d1a@samsung.com> <20160915130831.GJ13132@amd> <313cbae5-fd66-f0ae-79a9-a3f4273d6f9c@samsung.com> <20160916055927.GC13205@amd> Cc: Jacek Anaszewski , Richard Purdie , linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org, Marcel Holtmann From: David Lechner Message-ID: <2c48e1bf-ded8-223d-7077-30ee7e3e4e4c@lechnology.com> Date: Fri, 16 Sep 2016 10:32:16 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20160916055927.GC13205@amd> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - vern.gendns.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - lechnology.com X-Get-Message-Sender-Via: vern.gendns.com: authenticated_id: davidmain+lechnology.com/only user confirmed/virtual account not confirmed X-Authenticated-Sender: vern.gendns.com: davidmain@lechnology.com X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/16/2016 12:59 AM, Pavel Machek wrote: > Hi! > > +The current brightness is found by reading a single byte from the > character > +device. Values are unsigned: 0 to 255. Reading does not block and > always returns > +the most recent brightness value. The device node can also be polled > to notify > +when the brightness value changes. > > What is going on there? We have O_NONBLOCK, user should be able to > select if he wants blocking behaviour or not. I will look into this. > > And yes, there's interface for creating a LED, but not one for > deleting it? uleds.txt says "The LED class device will be removed when the open file handle to /dev/uleds is closed." Is this not clear? > > And... how is it going to work with multiple LEDs? Userspace gets > single bytes with brightness. How does it know to which LED the > brightness belongs? It looks like this is missing from uleds.txt. By opening multiple file handles to /dev/uleds, you can create multiple devices. Each file handle will return a different value when read that corresponds to the LEDs class device that belongs to it.