From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751532AbbCILvD (ORCPT ); Mon, 9 Mar 2015 07:51:03 -0400 Received: from unicorn.mansr.com ([81.2.72.234]:51185 "EHLO unicorn.mansr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751230AbbCILu6 convert rfc822-to-8bit (ORCPT ); Mon, 9 Mar 2015 07:50:58 -0400 From: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= To: Geert Uytterhoeven Cc: Pavel Machek , Alexandre Courbot , Felipe Balbi , Bryan Wu , Richard Purdie , "linux-leds\@vger.kernel.org" , Linux Kernel Mailing List , Linux OMAP Mailing List , "linux-gpio\@vger.kernel.org" Subject: Re: RGB LED control (was Re: "advanced" LED controllers) References: <20150219211424.GN13603@saruman.tx.rr.com> <20150302092111.GA19233@amd> <20150308205732.GA385@amd> Date: Mon, 09 Mar 2015 11:50:56 +0000 In-Reply-To: (Geert Uytterhoeven's message of "Mon, 9 Mar 2015 09:08:37 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Geert Uytterhoeven writes: > Hi Pavel, > > On Sun, Mar 8, 2015 at 9:57 PM, Pavel Machek wrote: >> Ok, so I played with RGB LED a bit, and we have quite a gap in >> documentation: what 50% brightness means is non-trivial and very >> important in case we want to do smooth blinking and color transitions. >> >> Signed-off-by: Pavel Machek >> >> diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led >> index 3646ec8..649d7a6 100644 >> --- a/Documentation/ABI/testing/sysfs-class-led >> +++ b/Documentation/ABI/testing/sysfs-class-led >> @@ -8,6 +8,11 @@ Description: >> non-zero brightness settings. The value is between 0 and >> /sys/class/leds//max_brightness. >> >> + If LED supports continuous brightness settings, 50% brightness >> + should correspond to 50% brightness perceived by human, in a similar >> + manner pixel brightness on monitor does (not 50% PWM). > > How many drivers do it right? How many don't? > > For those that don't, perhaps we handle the conversion between perceived and > pwm in the core, e.g. by adding a new flag to led_classdev.flags to indicate > the need for conversion? Some LED controllers do the right thing in hardware, so any adjustment done in the core needs to be optional. -- Måns Rullgård mans@mansr.com