After commit 
540b8bb9c33935183ceb5bed466a42ad72b2af56:
  sony-laptop: fingers off backlight if video.ko is serving this functionality
I can't set brightness on my sony laptop (nothing in /sys/class/backlight).
dmesg says "sony-laptop: Sony: Brightness ignored, must be controlled by ACPI
video driver".
The function acpi_video_backlight_support returns 0 if we should use the
vendor-specific backlight support, while non-0 if the ACPI generic should
be used. Because of this, the check introduced by the said commit appears
reversed.
Signed-off-by: Alessandro Guido <ag@alessandroguido.name>
Signed-off-by: Len Brown <len.brown@intel.com>
                goto outinput;
        }
 
-       if (!acpi_video_backlight_support()) {
+       if (acpi_video_backlight_support()) {
                printk(KERN_INFO DRV_PFX "Sony: Brightness ignored, must be "
                       "controlled by ACPI video driver\n");
        } else if (ACPI_SUCCESS(acpi_get_handle(sony_nc_acpi_handle, "GBRT",