From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [i915] Backlight brighter since 3.9.0 Date: Mon, 20 May 2013 23:55:34 +0200 Message-ID: <20130520215534.GX12292@phenom.ffwll.local> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wi0-f182.google.com (mail-wi0-f182.google.com [209.85.212.182]) by gabe.freedesktop.org (Postfix) with ESMTP id 6DA8BE5BF0 for ; Mon, 20 May 2013 14:54:36 -0700 (PDT) Received: by mail-wi0-f182.google.com with SMTP id c10so2506133wiw.3 for ; Mon, 20 May 2013 14:54:35 -0700 (PDT) Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dri-devel-bounces+sf-dri-devel=m.gmane.org@lists.freedesktop.org Errors-To: dri-devel-bounces+sf-dri-devel=m.gmane.org@lists.freedesktop.org To: Jan Hinnerk Stosch Cc: dri-devel@lists.freedesktop.org List-Id: dri-devel@lists.freedesktop.org On Sat, May 18, 2013 at 12:39:14AM +0200, Jan Hinnerk Stosch wrote: > Hallo, > > I hope this is the right place to ask, because I actually don't know > whether it is a bug or a feature that I'm experiencing since linux 3.9: > When I boot my system the backlight gets extremely bright compared to older > kernel versions. It is most obvious when I leave X (more a yellow than a > black background), but I have the impression, that the colors in X are > brighter than usual, too. > I used my spare time this afternoon to do a kernel bisect and learned that > the first "bad" commit is 55bc60db5988c8366751d3d04dd690698a53412c. As I > don't have insight or understanding of the code: Is this behaviour intended > and how could I change it to the old state or is it a bug and should I > report it somewhere? > My system is as follows: > Intel i5-3570k with Intel HD 4000 > my monitor is connected via HDMI. > If you need any more information just tell me. Yeah, this is a feature. HDMI has (for oddball backwards compat with analog TV signals) a special mode which reduces the useable RGB value range by chopping off about 10% at the bottom and top end. This results in light colors getting brighter and dark colors getting darker. The above mentioned commit tries (to the best of our knowledge) to auto-set the option which most likely fits what the hdmi sink will do with the color data. You can either fix this up in the hdmi sink with the on-screen menu or by manually setting the "RBG Broadcast" property for the relevant hdmi connector to the setting you want. Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch