i915 backlight failure on resume with 2.6.27

[Sergio Monteiro Basto]

On Tue, 2008-12-02 at 11:38 -0600, James Bottomley wrote:
> On Tue, 2008-12-02 at 13:08 +0000, Sergio Monteiro Basto wrote: 
> > On Mon, 2008-12-01 at 11:42 -0600, James Bottomley wrote:
> > > You probably remember the system, it's my fujitsu P7120 lifebook with
> > > the funny backlight wiring.
> > > 
> > > Previously, suspend/resume was made to work by saving the PCI state
> > > including the legacy backlight register setting (and worked just fine
> > > when invoked with a hal quirk).
> > > 
> > > On FC9, with the 2.6.26 fedora kernels, hal no longer does anything and
> > > relies on the i915 kernel driver.  This was perfectly fine, except that
> > > the backlight was now being restored to full brightness on resume rather
> > > than the setting on resume.  The other annoyance was that VT consoles
> > > were now lost on resume (switching to them produces a black screen,
> > > although switching back to vt7 where X is running is fine).
> > > 
> > > As of the 2.6.27 fedora kernels, the backlight is now off on resume,
> > > which is even more annoying.  It can be turned on by doing a VT switch,
> > > although all the console VTs are still blank, so there looks to be some
> > > bug in the i915 driver that crept in between 2.6.26 and 2.6.27.
> > 
> > Hum as quick answer , kernel fedora 2.6.27 have change _DOS thing.
> > So may be that is the problem.
> > The fedora patch is talked about on lkml
> > http://lkml.org/lkml/2008/11/10/233
> 

> Actually, they haven't.  I'm running  2.6.27.5-41.fc9.i686 and if I look
> in the kernel SRPM for that kernel (by building it) the relevant area of
> drivers/acpi/video.c is
> 

ok , I forgot , fedora kernels 2.6.27 for fc10.  Also don't know the
state of Arlied drm stuff, if it is only on fc10 or not .

I trace this information on : 
http://koji.fedoraproject.org/koji/packageinfo?packageID=8



> /* acpi_video interface */
> 
> static int acpi_video_bus_start_devices(struct acpi_video_bus *video)
> {
>         return acpi_video_bus_DOS(video, 0, 0);
> }
> 
> static int acpi_video_bus_stop_devices(struct acpi_video_bus *video)
> {
>         return acpi_video_bus_DOS(video, 0, 1);
> }
> 
> So nothing's changed in that area since 2.6.26.
> 
> It could still be a disagreement between ACPI, BIOS and the driver over
> who turns on the backlight, but the loss of the text console strongly
> suggests that something is slightly wrong with the VGA modes.
> 
> > About this _DOS , I reported this problem a long time ago, which now
> > is on http://bugzilla.kernel.org/show_bug.cgi?id=6001
> 
> James
> 
> 
-- 
Sérgio M. B.
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