From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Mack Subject: Re: Strange effect with i915 backlight controller Date: Thu, 10 Nov 2011 16:11:29 +0100 Message-ID: <4EBBE9A1.8020501@gmail.com> References: <4EB3F860.6010408@gmail.com> <4EB87E6A.3060403@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4EB87E6A.3060403@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: dri-devel@lists.freedesktop.org Cc: jbarnes@virtuousgeek.org, harald@redhat.com, Keith Packard , linux-kernel@vger.kernel.org List-Id: dri-devel@lists.freedesktop.org On 11/08/2011 01:57 AM, Daniel Mack wrote: > Didn't get any response yet, hence copying LKML for a broader audience. Nobody, really? This is a rather annoying regression, as touching the brightness keys appearantly switches off the whole machine. I'm sure this is trivial to fix, I just don't have the insight of this driver and the chipset. Any pointer greatly appreciated, and I can test patches. Thanks, Daniel > > On 11/04/2011 03:36 PM, Daniel Mack wrote: >> I'm facing a bug on a Samsung X20 notebook which features an i915 >> chipset (output of 'lspci -v' attached). >> >> The effect is that setting the backlight to odd values causes the value >> to be misinterpreted. Harald Hoyer (cc:) had the same thing on a Netbook >> (I don't recall which model it was). >> >> So this will turn the backlight to full brightness: >> >> # cat /sys/class/backlight/intel_backlight/max_brightness >> 29750 >> # echo 29750 > /sys/class/backlight/intel_backlight/brightness >> >> However, writing 29749 will turn the display backlight off, and 29748 >> appears to be the next valid lower value. >> >> It seems like the IS_PINEVIEW() branch in >> drivers/gpu/drm/i915/intel_panel.c:intel_panel_actually_set_backlight() >> could do the right thing, but this code is written for an entirely >> different model, right? >> >> I can reproduce this on 3.0 and 3.1 vanilla as well as with the current >> mainline git. >> >> Let me know if there is any patch that I can test. >> >> >> Thanks, >> Daniel >