linux-kernel - Re: [PATCH] drm/kms: fix fbdev blanking regression

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Message-ID: <alpine.LFD.2.00.1001161558380.18503@casper.infradead.org>
Date:	Sat, 16 Jan 2010 16:02:21 +0000 (GMT)
From:	James Simmons <jsimmons@...radead.org>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
cc:	David John <davidjon@...ontk.org>,
	Johan Hovold <jhovold@...il.com>,
	Dave Airlie <airlied@...hat.com>,
	dri-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	Eric Anholt <eric@...olt.net>
Subject: Re: [PATCH] drm/kms: fix fbdev blanking regression


> > > On 01/07/2010 12:42 AM, Johan Hovold wrote:
> > > >> Yeap. The fix uncovered a bug in your driver. I haven't heard of
> > > >> problems with the other drm drivers.
> > > >>  
> > > >>> The backlight is handled via the DRI driver I assume. At least
> > > >>> i9xx_crtc_dpms is called on powerdown.
> > > >>
> > > >> Can you post your dmesg and kernel config.
> > > 
> > > [snip]
> > > 
> > > Adding the Intel DRM people in CC as well. I have the same issue
> > > with my GM45.
> > 
> > Okay I looked at the code to figure out what is happening and why
> > only this driver has problems. The problem is that the framebuffer
> > layer expects the backlight to be a seperate device. The reason being
> > is that some embedded systems will use a gpio backlight. That way
> > power management for a graphics card/backlight has 3 seperate states.
> > Currently the intel DRM driver treats the backlight as being apart of
> > the encoder. Jesse do you have objections to having the intel driver
> > expose a backlight device. The bonus of that is the user can also set
> > the backlight levels.
> 
> On Intel we usually expect the backlight to be exposed by ACPI or a
> platform driver.  On recent platforms, the ACPI driver will actually
> send requests to the gfx driver to do the actual register writes to
> adjust the backlight, but it's still ACPI driven.
> 
> Maybe we just need to wire up the fb backlight hooks appropriately?

I'm about to work up a patch And I noticed that drm-next and 
drm-intel-next are very different. Which tree should I use? Second is it 
possible for a card to support more than one backlight.
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