Merge tag 'acpi-video-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull ACPI video support fixes from Rafael Wysocki:
 "I'm sending a separate pull request for this as it may be somewhat
  controversial.  The breakage addressed here is not really new and the
  fixes may not satisfy all users of the affected systems, but we've had
  so much back and forth dance in this area over the last several weeks
  that I think it's time to actually make some progress.

  The source of the problem is that about a year ago we started to tell
  BIOSes that we're compatible with Windows 8, which we really need to
  do, because some systems shipping with Windows 8 are tested with it
  and nothing else, so if we tell their BIOSes that we aren't compatible
  with Windows 8, we expose our users to untested BIOS/AML code paths.

  However, as it turns out, some Windows 8-specific AML code paths are
  not tested either, because Windows 8 actually doesn't use the ACPI
  methods containing them, so if we declare Windows 8 compatibility and
  attempt to use those ACPI methods, things break.  That occurs mostly
  in the backlight support area where in particular the _BCM and _BQC
  methods are plain unusable on some systems if the OS declares Windows
  8 compatibility.

  [ The additional twist is that they actually become usable if the OS
    says it is not compatible with Windows 8, but that may cause
    problems to show up elsewhere ]

  Investigation carried out by Matthew Garrett indicates that what
  Windows 8 does about backlight is to leave backlight control up to
  individual graphics drivers.  At least there's evidence that it does
  that if the Intel graphics driver is used, so we've decided to follow
  Windows 8 in that respect and allow i915 to control backlight (Daniel
  likes that part).

  The first commit from Aaron Lu makes ACPICA export the variable from
  which we can infer whether or not the BIOS believes that we are
  compatible with Windows 8.

  The second commit from Matthew Garrett prepares the ACPI video driver
  by making it initialize the ACPI backlight even if it is not going to
  be used afterward (that is needed for backlight control to work on
  Thinkpads).

  The third commit implements the actual workaround making i915 take
  over backlight control if the firmware thinks it's dealing with
  Windows 8 and is based on the work of multiple developers, including
  Matthew Garrett, Chun-Yi Lee, Seth Forshee, and Aaron Lu.

  The final commit from Aaron Lu makes us follow Windows 8 by informing
  the firmware through the _DOS method that it should not carry out
  automatic brightness changes, so that brightness can be controlled by
  GUI.

  Hopefully, this approach will allow us to avoid using blacklists of
  systems that should not declare Windows 8 compatibility just to avoid
  backlight control problems in the future.

   - Change from Aaron Lu makes ACPICA export a variable which can be
     used by driver code to determine whether or not the BIOS believes
     that we are compatible with Windows 8.

   - Change from Matthew Garrett makes the ACPI video driver initialize
     the ACPI backlight even if it is not going to be used afterward
     (that is needed for backlight control to work on Thinkpads).

   - Fix from Rafael J Wysocki implements Windows 8 backlight support
     workaround making i915 take over bakclight control if the firmware
     thinks it's dealing with Windows 8.  Based on the work of multiple
     developers including Matthew Garrett, Chun-Yi Lee, Seth Forshee,
     and Aaron Lu.

   - Fix from Aaron Lu makes the kernel follow Windows 8 by informing
     the firmware through the _DOS method that it should not carry out
     automatic brightness changes, so that brightness can be controlled
     by GUI"

* tag 'acpi-video-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  ACPI / video: no automatic brightness changes by win8-compatible firmware
  ACPI / video / i915: No ACPI backlight if firmware expects Windows 8
  ACPI / video: Always call acpi_video_init_brightness() on init
  ACPICA: expose OSI version

4 files changed, 27 insertions, 1 deletions

diff --git a/include/acpi/acpixf.h b/include/acpi/acpixf.h
index 1b09300810e6..22d497ee6ef9 100644
--- a/include/acpi/acpixf.h
+++ b/include/acpi/acpixf.h
@@ -62,6 +62,7 @@ extern u32 acpi_current_gpe_count;
 extern struct acpi_table_fadt acpi_gbl_FADT;
 extern u8 acpi_gbl_system_awake_and_running;
 extern u8 acpi_gbl_reduced_hardware;	/* ACPI 5.0 */
+extern u8 acpi_gbl_osi_data;
 
 /* Runtime configuration of debug print levels */
 
diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h
index a64adcc29ae5..22b03c9286e9 100644
--- a/include/acpi/actypes.h
+++ b/include/acpi/actypes.h
@@ -1144,4 +1144,19 @@ struct acpi_memory_list {
 #endif
 };
 
+/* Definitions for _OSI support */
+
+#define ACPI_OSI_WIN_2000               0x01
+#define ACPI_OSI_WIN_XP                 0x02
+#define ACPI_OSI_WIN_XP_SP1             0x03
+#define ACPI_OSI_WINSRV_2003            0x04
+#define ACPI_OSI_WIN_XP_SP2             0x05
+#define ACPI_OSI_WINSRV_2003_SP1        0x06
+#define ACPI_OSI_WIN_VISTA              0x07
+#define ACPI_OSI_WINSRV_2008            0x08
+#define ACPI_OSI_WIN_VISTA_SP1          0x09
+#define ACPI_OSI_WIN_VISTA_SP2          0x0A
+#define ACPI_OSI_WIN_7                  0x0B
+#define ACPI_OSI_WIN_8                  0x0C
+
 #endif				/* __ACTYPES_H__ */
diff --git a/include/acpi/video.h b/include/acpi/video.h
index 61109f2609fc..b26dc4fb7ba8 100644
--- a/include/acpi/video.h
+++ b/include/acpi/video.h
@@ -17,12 +17,21 @@ struct acpi_device;
 #define ACPI_VIDEO_DISPLAY_LEGACY_TV      0x0200
 
 #if (defined CONFIG_ACPI_VIDEO || defined CONFIG_ACPI_VIDEO_MODULE)
-extern int acpi_video_register(void);
+extern int __acpi_video_register(bool backlight_quirks);
+static inline int acpi_video_register(void)
+{
+	return __acpi_video_register(false);
+}
+static inline int acpi_video_register_with_quirks(void)
+{
+	return __acpi_video_register(true);
+}
 extern void acpi_video_unregister(void);
 extern int acpi_video_get_edid(struct acpi_device *device, int type,
 			       int device_id, void **edid);
 #else
 static inline int acpi_video_register(void) { return 0; }
+static inline int acpi_video_register_with_quirks(void) { return 0; }
 static inline void acpi_video_unregister(void) { return; }
 static inline int acpi_video_get_edid(struct acpi_device *device, int type,
 				      int device_id, void **edid)
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 353ba256f368..6ad72f92469c 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -191,6 +191,7 @@ extern bool wmi_has_guid(const char *guid);
 #define ACPI_VIDEO_BACKLIGHT_DMI_VIDEO			0x0200
 #define ACPI_VIDEO_OUTPUT_SWITCHING_DMI_VENDOR		0x0400
 #define ACPI_VIDEO_OUTPUT_SWITCHING_DMI_VIDEO		0x0800
+#define ACPI_VIDEO_SKIP_BACKLIGHT			0x1000
 
 #if defined(CONFIG_ACPI_VIDEO) || defined(CONFIG_ACPI_VIDEO_MODULE)