ACPI: Populate DIDL before registering ACPI video device on Intel

Intel graphics hardware that implements the ACPI IGD OpRegion spec
requires that the list of display devices be populated before any ACPI
video methods are called. Detect when this is the case and defer
registration until the opregion code calls it. Fixes crashes on HP
laptops.

http://bugzilla.kernel.org/show_bug.cgi?id=11259

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Len Brown <len.brown@intel.com>

include/acpi/video.h

@@ -0,0 +1,11 @@
+#ifndef __ACPI_VIDEO_H
+#define __ACPI_VIDEO_H
+
+#if (defined CONFIG_ACPI_VIDEO || defined CONFIG_ACPI_VIDEO_MODULE)
+extern int acpi_video_register(void);
+#else
+static inline int acpi_video_register(void) { return 0; }
+#endif
+
+#endif
+