fix backlight resets to minium when changing resolution

[Liu Xinyun <xinyun.liu@intel.com>]

It is reported as https://bugs.freedesktop.org/show_bug.cgi?id=29716.
find the regression and here is the fix, maybe ugly.



diff --git a/src/intel_display.c b/src/intel_display.c
index d32224e..4a159bf 100644
--- a/src/intel_display.c
+++ b/src/intel_display.c
@@ -339,6 +339,8 @@ intel_crtc_apply(xf86CrtcPtr crtc)

                if (output->crtc != crtc)
                        continue;
+               /* Turn on any outputs on this crtc that may have been disabled */
+               intel_output_dpms(output, DPMSModeOn);

                intel_output = output->driver_private;
                output_ids[output_count] =
--------

this regression is caused by this commit. In fact, KMS doesn't not handle 
backlight properly as we think. I don't know where to put the code, so I 
use above code in xf86-intel-driver to fix this issue.

In fact, KMS initialize mode as DPMSOFF, and X set to it to ON after start.
And if any mode is changed, it will set to 'correct' status: OFF. Thus xrandr can
not change backlight any more. So a better solution shoule be there. Any suggestion?

19c48d3b3f33582baa87a9b3a9189e320e4cea45 is the first bad commit
commit 19c48d3b3f33582baa87a9b3a9189e320e4cea45
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Mon Aug 9 10:13:58 2010 +0100

    display: outputs are enabled automatically by KMS

    When an output is attached to a crtc and that crtc is enabled, the
    output is automatically enabled so we can remove the redundant manual
    dpms on.

    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>



Regards,
Xinyun