Merge branch 'acpi-doc'

* acpi-doc:
  Documentation / CPU hotplug: Rephrase the outdated description for MADT entries
  ACPI / video: update video_extension.txt for backlight control
  ACPI / video: move video_extension.txt to Documentation/acpi
  ACPI / video: add description for brightness_switch_enabled
  ACPI: Add ACPI namespace documentation
  ACPI: Add sysfs ABI documentation
  ACPI: Update MAINTAINERS file to include Documentation/acpi

8 files changed, 575 insertions, 40 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-acpi b/Documentation/ABI/testing/sysfs-bus-acpi
new file mode 100644
index 000000000000..7fa9cbc75344
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-acpi
@@ -0,0 +1,58 @@
+What:		/sys/bus/acpi/devices/.../path
+Date:		December 2006
+Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+		This attribute indicates the full path of ACPI namespace
+		object associated with the device object.  For example,
+		\_SB_.PCI0.
+		This file is not present for device objects representing
+		fixed ACPI hardware features (like power and sleep
+		buttons).
+
+What:		/sys/bus/acpi/devices/.../modalias
+Date:		July 2007
+Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+		This attribute indicates the PNP IDs of the device object.
+		That is acpi:HHHHHHHH:[CCCCCCC:].  Where each HHHHHHHH or
+		CCCCCCCC contains device object's PNPID (_HID or _CID).
+
+What:		/sys/bus/acpi/devices/.../hid
+Date:		April 2005
+Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+		This attribute indicates the hardware ID (_HID) of the
+		device object.  For example, PNP0103.
+		This file is present for device objects having the _HID
+		control method.
+
+What:		/sys/bus/acpi/devices/.../description
+Date:		October 2012
+Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+		This attribute contains the output of the device object's
+		_STR control method, if present.
+
+What:		/sys/bus/acpi/devices/.../adr
+Date:		October 2012
+Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+		This attribute contains the output of the device object's
+		_ADR control method, which is present for ACPI device
+		objects representing devices having standard enumeration
+		algorithms, such as PCI.
+
+What:		/sys/bus/acpi/devices/.../uid
+Date:		October 2012
+Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+		This attribute contains the output of the device object's
+		_UID control method, if present.
+
+What:		/sys/bus/acpi/devices/.../eject
+Date:		December 2006
+Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+		Writing 1 to this attribute will trigger hot removal of
+		this device object.  This file exists for every device
+		object that has _EJ0 method.
diff --git a/Documentation/ABI/testing/sysfs-devices-sun b/Documentation/ABI/testing/sysfs-devices-sun
index 86be9848a77e..625ce4b63758 100644
--- a/Documentation/ABI/testing/sysfs-devices-sun
+++ b/Documentation/ABI/testing/sysfs-devices-sun
@@ -1,4 +1,4 @@
-Whatt:		/sys/devices/.../sun
+What:		/sys/devices/.../sun
 Date:		October 2012
 Contact:	Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
 Description:
diff --git a/Documentation/acpi/namespace.txt b/Documentation/acpi/namespace.txt
new file mode 100644
index 000000000000..260f6a3661fa
--- /dev/null
+++ b/Documentation/acpi/namespace.txt
@@ -0,0 +1,395 @@
+ACPI Device Tree - Representation of ACPI Namespace
+
+Copyright (C) 2013, Intel Corporation
+Author: Lv Zheng <lv.zheng@intel.com>
+
+
+Abstract:
+
+The Linux ACPI subsystem converts ACPI namespace objects into a Linux
+device tree under the /sys/devices/LNXSYSTEM:00 and updates it upon
+receiving ACPI hotplug notification events.  For each device object in this
+hierarchy there is a corresponding symbolic link in the
+/sys/bus/acpi/devices.
+This document illustrates the structure of the ACPI device tree.
+
+
+Credit:
+
+Thanks for the help from Zhang Rui <rui.zhang@intel.com> and Rafael J.
+Wysocki <rafael.j.wysocki@intel.com>.
+
+
+1. ACPI Definition Blocks
+
+   The ACPI firmware sets up RSDP (Root System Description Pointer) in the
+   system memory address space pointing to the XSDT (Extended System
+   Description Table).  The XSDT always points to the FADT (Fixed ACPI
+   Description Table) using its first entry, the data within the FADT
+   includes various fixed-length entries that describe fixed ACPI features
+   of the hardware.  The FADT contains a pointer to the DSDT
+   (Differentiated System Descripition Table).  The XSDT also contains
+   entries pointing to possibly multiple SSDTs (Secondary System
+   Description Table).
+
+   The DSDT and SSDT data is organized in data structures called definition
+   blocks that contain definitions of various objects, including ACPI
+   control methods, encoded in AML (ACPI Machine Language).  The data block
+   of the DSDT along with the contents of SSDTs represents a hierarchical
+   data structure called the ACPI namespace whose topology reflects the
+   structure of the underlying hardware platform.
+
+   The relationships between ACPI System Definition Tables described above
+   are illustrated in the following diagram.
+
+     +---------+    +-------+    +--------+    +------------------------+
+     |  RSDP   | +->| XSDT  | +->|  FADT  |    |  +-------------------+ |
+     +---------+ |  +-------+ |  +--------+  +-|->|       DSDT        | |
+     | Pointer | |  | Entry |-+  | ...... |  | |  +-------------------+ |
+     +---------+ |  +-------+    | X_DSDT |--+ |  | Definition Blocks | |
+     | Pointer |-+  | ..... |    | ...... |    |  +-------------------+ |
+     +---------+    +-------+    +--------+    |  +-------------------+ |
+                    | Entry |------------------|->|       SSDT        | |
+                    +- - - -+                  |  +-------------------| |
+                    | Entry | - - - - - - - -+ |  | Definition Blocks | |
+                    +- - - -+                | |  +-------------------+ |
+                                             | |  +- - - - - - - - - -+ |
+                                             +-|->|       SSDT        | |
+                                               |  +-------------------+ |
+                                               |  | Definition Blocks | |
+                                               |  +- - - - - - - - - -+ |
+                                               +------------------------+
+                                                           |
+                                              OSPM Loading |
+                                                          \|/
+                                                    +----------------+
+                                                    | ACPI Namespace |
+                                                    +----------------+
+
+                     Figure 1. ACPI Definition Blocks
+
+   NOTE: RSDP can also contain a pointer to the RSDT (Root System
+         Description Table).  Platforms provide RSDT to enable
+         compatibility with ACPI 1.0 operating systems.  The OS is expected
+         to use XSDT, if present.
+
+
+2. Example ACPI Namespace
+
+   All definition blocks are loaded into a single namespace.  The namespace
+   is a hierarchy of objects identified by names and paths.
+   The following naming conventions apply to object names in the ACPI
+   namespace:
+   1. All names are 32 bits long.
+   2. The first byte of a name must be one of 'A' - 'Z', '_'.
+   3. Each of the remaining bytes of a name must be one of 'A' - 'Z', '0'
+      - '9', '_'.
+   4. Names starting with '_' are reserved by the ACPI specification.
+   5. The '\' symbol represents the root of the namespace (i.e. names
+      prepended with '\' are relative to the namespace root).
+   6. The '^' symbol represents the parent of the current namespace node
+      (i.e. names prepended with '^' are relative to the parent of the
+      current namespace node).
+
+   The figure below shows an example ACPI namespace.
+
+   +------+
+   | \    |                     Root
+   +------+
+     |
+     | +------+
+     +-| _PR  |                 Scope(_PR): the processor namespace
+     | +------+
+     |   |
+     |   | +------+
+     |   +-| CPU0 |             Processor(CPU0): the first processor
+     |     +------+
+     |
+     | +------+
+     +-| _SB  |                 Scope(_SB): the system bus namespace
+     | +------+
+     |   |
+     |   | +------+
+     |   +-| LID0 |             Device(LID0); the lid device
+     |   | +------+
+     |   |   |
+     |   |   | +------+
+     |   |   +-| _HID |         Name(_HID, "PNP0C0D"): the hardware ID
+     |   |   | +------+
+     |   |   |
+     |   |   | +------+
+     |   |   +-| _STA |         Method(_STA): the status control method
+     |   |     +------+
+     |   |
+     |   | +------+
+     |   +-| PCI0 |             Device(PCI0); the PCI root bridge
+     |     +------+
+     |       |
+     |       | +------+
+     |       +-| _HID |         Name(_HID, "PNP0A08"): the hardware ID
+     |       | +------+
+     |       |
+     |       | +------+
+     |       +-| _CID |         Name(_CID, "PNP0A03"): the compatible ID
+     |       | +------+
+     |       |
+     |       | +------+
+     |       +-| RP03 |         Scope(RP03): the PCI0 power scope
+     |       | +------+
+     |       |   |
+     |       |   | +------+
+     |       |   +-| PXP3 |     PowerResource(PXP3): the PCI0 power resource
+     |       |     +------+
+     |       |
+     |       | +------+
+     |       +-| GFX0 |         Device(GFX0): the graphics adapter
+     |         +------+
+     |           |
+     |           | +------+
+     |           +-| _ADR |     Name(_ADR, 0x00020000): the PCI bus address
+     |           | +------+
+     |           |
+     |           | +------+
+     |           +-| DD01 |     Device(DD01): the LCD output device
+     |             +------+
+     |               |
+     |               | +------+
+     |               +-| _BCL | Method(_BCL): the backlight control method
+     |                 +------+
+     |
+     | +------+
+     +-| _TZ  |                 Scope(_TZ): the thermal zone namespace
+     | +------+
+     |   |
+     |   | +------+
+     |   +-| FN00 |             PowerResource(FN00): the FAN0 power resource
+     |   | +------+
+     |   |
+     |   | +------+
+     |   +-| FAN0 |             Device(FAN0): the FAN0 cooling device
+     |   | +------+
+     |   |   |
+     |   |   | +------+
+     |   |   +-| _HID |         Name(_HID, "PNP0A0B"): the hardware ID
+     |   |     +------+
+     |   |
+     |   | +------+
+     |   +-| TZ00 |             ThermalZone(TZ00); the FAN thermal zone
+     |     +------+
+     |
+     | +------+
+     +-| _GPE |                 Scope(_GPE): the GPE namespace
+       +------+
+
+                     Figure 2. Example ACPI Namespace
+
+
+3. Linux ACPI Device Objects
+
+   The Linux kernel's core ACPI subsystem creates struct acpi_device
+   objects for ACPI namespace objects representing devices, power resources
+   processors, thermal zones.  Those objects are exported to user space via
+   sysfs as directories in the subtree under /sys/devices/LNXSYSTM:00.  The
+   format of their names is <bus_id:instance>, where 'bus_id' refers to the
+   ACPI namespace representation of the given object and 'instance' is used
+   for distinguishing different object of the same 'bus_id' (it is
+   two-digit decimal representation of an unsigned integer).
+
+   The value of 'bus_id' depends on the type of the object whose name it is
+   part of as listed in the table below.
+
+                +---+-----------------+-------+----------+
+                |   | Object/Feature  | Table | bus_id   |
+                +---+-----------------+-------+----------+
+                | N | Root            | xSDT  | LNXSYSTM |
+                +---+-----------------+-------+----------+
+                | N | Device          | xSDT  | _HID     |
+                +---+-----------------+-------+----------+
+                | N | Processor       | xSDT  | LNXCPU   |
+                +---+-----------------+-------+----------+
+                | N | ThermalZone     | xSDT  | LNXTHERM |
+                +---+-----------------+-------+----------+
+                | N | PowerResource   | xSDT  | LNXPOWER |
+                +---+-----------------+-------+----------+
+                | N | Other Devices   | xSDT  | device   |
+                +---+-----------------+-------+----------+
+                | F | PWR_BUTTON      | FADT  | LNXPWRBN |
+                +---+-----------------+-------+----------+
+                | F | SLP_BUTTON      | FADT  | LNXSLPBN |
+                +---+-----------------+-------+----------+
+                | M | Video Extension | xSDT  | LNXVIDEO |
+                +---+-----------------+-------+----------+
+                | M | ATA Controller  | xSDT  | LNXIOBAY |
+                +---+-----------------+-------+----------+
+                | M | Docking Station | xSDT  | LNXDOCK  |
+                +---+-----------------+-------+----------+
+
+                 Table 1. ACPI Namespace Objects Mapping
+
+   The following rules apply when creating struct acpi_device objects on
+   the basis of the contents of ACPI System Description Tables (as
+   indicated by the letter in the first column and the notation in the
+   second column of the table above):
+   N:
+      The object's source is an ACPI namespace node (as indicated by the
+      named object's type in the second column).  In that case the object's
+      directory in sysfs will contain the 'path' attribute whose value is
+      the full path to the node from the namespace root.
+      struct acpi_device objects are created for the ACPI namespace nodes
+      whose _STA control methods return PRESENT or FUNCTIONING.  The power
+      resource nodes or nodes without _STA are assumed to be both PRESENT
+      and FUNCTIONING.
+   F:
+      The struct acpi_device object is created for a fixed hardware
+      feature (as indicated by the fixed feature flag's name in the second
+      column), so its sysfs directory will not contain the 'path'
+      attribute.
+   M:
+      The struct acpi_device object is created for an ACPI namespace node
+      with specific control methods (as indicated by the ACPI defined
+      device's type in the second column).  The 'path' attribute containing
+      its namespace path will be present in its sysfs directory.  For
+      example, if the _BCL method is present for an ACPI namespace node, a
+      struct acpi_device object with LNXVIDEO 'bus_id' will be created for
+      it.
+
+   The third column of the above table indicates which ACPI System
+   Description Tables contain information used for the creation of the
+   struct acpi_device objects represented by the given row (xSDT means DSDT
+   or SSDT).
+
+   The forth column of the above table indicates the 'bus_id' generation
+   rule of the struct acpi_device object:
+   _HID:
+      _HID in the last column of the table means that the object's bus_id
+      is derived from the _HID/_CID identification objects present under
+      the corresponding ACPI namespace node. The object's sysfs directory
+      will then contain the 'hid' and 'modalias' attributes that can be
+      used to retrieve the _HID and _CIDs of that object.
+   LNXxxxxx:
+      The 'modalias' attribute is also present for struct acpi_device
+      objects having bus_id of the "LNXxxxxx" form (pseudo devices), in
+      which cases it contains the bus_id string itself.
+   device:
+      'device' in the last column of the table indicates that the object's
+      bus_id cannot be determined from _HID/_CID of the corresponding
+      ACPI namespace node, although that object represents a device (for
+      example, it may be a PCI device with _ADR defined and without _HID
+      or _CID).  In that case the string 'device' will be used as the
+      object's bus_id.
+
+
+4. Linux ACPI Physical Device Glue
+
+   ACPI device (i.e. struct acpi_device) objects may be linked to other
+   objects in the Linux' device hierarchy that represent "physical" devices
+   (for example, devices on the PCI bus).  If that happens, it means that
+   the ACPI device object is a "companion" of a device otherwise
+   represented in a different way and is used (1) to provide configuration
+   information on that device which cannot be obtained by other means and
+   (2) to do specific things to the device with the help of its ACPI
+   control methods.  One ACPI device object may be linked this way to
+   multiple "physical" devices.
+
+   If an ACPI device object is linked to a "physical" device, its sysfs
+   directory contains the "physical_node" symbolic link to the sysfs
+   directory of the target device object.  In turn, the target device's
+   sysfs directory will then contain the "firmware_node" symbolic link to
+   the sysfs directory of the companion ACPI device object.
+   The linking mechanism relies on device identification provided by the
+   ACPI namespace.  For example, if there's an ACPI namespace object
+   representing a PCI device (i.e. a device object under an ACPI namespace
+   object representing a PCI bridge) whose _ADR returns 0x00020000 and the
+   bus number of the parent PCI bridge is 0, the sysfs directory
+   representing the struct acpi_device object created for that ACPI
+   namespace object will contain the 'physical_node' symbolic link to the
+   /sys/devices/pci0000:00/0000:00:02:0/ sysfs directory of the
+   corresponding PCI device.
+
+   The linking mechanism is generally bus-specific.  The core of its
+   implementation is located in the drivers/acpi/glue.c file, but there are
+   complementary parts depending on the bus types in question located
+   elsewhere.  For example, the PCI-specific part of it is located in
+   drivers/pci/pci-acpi.c.
+
+
+5. Example Linux ACPI Device Tree
+
+   The sysfs hierarchy of struct acpi_device objects corresponding to the
+   example ACPI namespace illustrated in Figure 2 with the addition of
+   fixed PWR_BUTTON/SLP_BUTTON devices is shown below.
+
+   +--------------+---+-----------------+
+   | LNXSYSTEM:00 | \ | acpi:LNXSYSTEM: |
+   +--------------+---+-----------------+
+     |
+     | +-------------+-----+----------------+
+     +-| LNXPWRBN:00 | N/A | acpi:LNXPWRBN: |
+     | +-------------+-----+----------------+
+     |
+     | +-------------+-----+----------------+
+     +-| LNXSLPBN:00 | N/A | acpi:LNXSLPBN: |
+     | +-------------+-----+----------------+
+     |
+     | +-----------+------------+--------------+
+     +-| LNXCPU:00 | \_PR_.CPU0 | acpi:LNXCPU: |
+     | +-----------+------------+--------------+
+     |
+     | +-------------+-------+----------------+
+     +-| LNXSYBUS:00 | \_SB_ | acpi:LNXSYBUS: |
+     | +-------------+-------+----------------+
+     |   |
+     |   | +- - - - - - - +- - - - - - +- - - - - - - -+
+     |   +-| * PNP0C0D:00 | \_SB_.LID0 | acpi:PNP0C0D: |
+     |   | +- - - - - - - +- - - - - - +- - - - - - - -+
+     |   |
+     |   | +------------+------------+-----------------------+
+     |   +-| PNP0A08:00 | \_SB_.PCI0 | acpi:PNP0A08:PNP0A03: |
+     |     +------------+------------+-----------------------+
+     |       |
+     |       | +-----------+-----------------+-----+
+     |       +-| device:00 | \_SB_.PCI0.RP03 | N/A |
+     |       | +-----------+-----------------+-----+
+     |       |   |
+     |       |   | +-------------+----------------------+----------------+
+     |       |   +-| LNXPOWER:00 | \_SB_.PCI0.RP03.PXP3 | acpi:LNXPOWER: |
+     |       |     +-------------+----------------------+----------------+
+     |       |
+     |       | +-------------+-----------------+----------------+
+     |       +-| LNXVIDEO:00 | \_SB_.PCI0.GFX0 | acpi:LNXVIDEO: |
+     |         +-------------+-----------------+----------------+
+     |           |
+     |           | +-----------+-----------------+-----+
+     |           +-| device:01 | \_SB_.PCI0.DD01 | N/A |
+     |             +-----------+-----------------+-----+
+     |
+     | +-------------+-------+----------------+
+     +-| LNXSYBUS:01 | \_TZ_ | acpi:LNXSYBUS: |
+       +-------------+-------+----------------+
+         |
+         | +-------------+------------+----------------+
+         +-| LNXPOWER:0a | \_TZ_.FN00 | acpi:LNXPOWER: |
+         | +-------------+------------+----------------+
+         |
+         | +------------+------------+---------------+
+         +-| PNP0C0B:00 | \_TZ_.FAN0 | acpi:PNP0C0B: |
+         | +------------+------------+---------------+
+         |
+         | +-------------+------------+----------------+
+         +-| LNXTHERM:00 | \_TZ_.TZ00 | acpi:LNXTHERM: |
+           +-------------+------------+----------------+
+
+                  Figure 3. Example Linux ACPI Device Tree
+
+   NOTE: Each node is represented as "object/path/modalias", where:
+         1. 'object' is the name of the object's directory in sysfs.
+         2. 'path' is the ACPI namespace path of the corresponding
+            ACPI namespace object, as returned by the object's 'path'
+            sysfs attribute.
+         3. 'modalias' is the value of the object's 'modalias' sysfs
+            attribute (as described earlier in this document).
+   NOTE: N/A indicates the device object does not have the 'path' or the
+         'modalias' attribute.
+   NOTE: The PNP0C0D device listed above is highlighted (marked by "*")
+         to indicate it will be created only when its _STA methods return
+         PRESENT or FUNCTIONING.
diff --git a/Documentation/acpi/video_extension.txt b/Documentation/acpi/video_extension.txt
new file mode 100644
index 000000000000..78b32ac02466
--- /dev/null
+++ b/Documentation/acpi/video_extension.txt
@@ -0,0 +1,106 @@
+ACPI video extensions
+~~~~~~~~~~~~~~~~~~~~~
+
+This driver implement the ACPI Extensions For Display Adapters for
+integrated graphics devices on motherboard, as specified in ACPI 2.0
+Specification, Appendix B, allowing to perform some basic control like
+defining the video POST device, retrieving EDID information or to
+setup a video output, etc.  Note that this is an ref. implementation
+only.  It may or may not work for your integrated video device.
+
+The ACPI video driver does 3 things regarding backlight control:
+
+1 Export a sysfs interface for user space to control backlight level
+
+If the ACPI table has a video device, and acpi_backlight=vendor kernel
+command line is not present, the driver will register a backlight device
+and set the required backlight operation structure for it for the sysfs
+interface control. For every registered class device, there will be a
+directory named acpi_videoX under /sys/class/backlight.
+
+The backlight sysfs interface has a standard definition here:
+Documentation/ABI/stable/sysfs-class-backlight.
+
+And what ACPI video driver does is:
+actual_brightness: on read, control method _BQC will be evaluated to
+get the brightness level the firmware thinks it is at;
+bl_power: not implemented, will set the current brightness instead;
+brightness: on write, control method _BCM will run to set the requested
+brightness level;
+max_brightness: Derived from the _BCL package(see below);
+type: firmware
+
+Note that ACPI video backlight driver will always use index for
+brightness, actual_brightness and max_brightness. So if we have
+the following _BCL package:
+
+Method (_BCL, 0, NotSerialized)
+{
+	Return (Package (0x0C)
+	{
+		0x64,
+		0x32,
+		0x0A,
+		0x14,
+		0x1E,
+		0x28,
+		0x32,
+		0x3C,
+		0x46,
+		0x50,
+		0x5A,
+		0x64
+	})
+}
+
+The first two levels are for when laptop are on AC or on battery and are
+not used by Linux currently. The remaining 10 levels are supported levels
+that we can choose from. The applicable index values are from 0 (that
+corresponds to the 0x0A brightness value) to 9 (that corresponds to the
+0x64 brightness value) inclusive. Each of those index values is regarded
+as a "brightness level" indicator. Thus from the user space perspective
+the range of available brightness levels is from 0 to 9 (max_brightness)
+inclusive.
+
+2 Notify user space about hotkey event
+
+There are generally two cases for hotkey event reporting:
+i) For some laptops, when user presses the hotkey, a scancode will be
+   generated and sent to user space through the input device created by
+   the keyboard driver as a key type input event, with proper remap, the
+   following key code will appear to user space:
+
+	EV_KEY, KEY_BRIGHTNESSUP
+	EV_KEY, KEY_BRIGHTNESSDOWN
+	etc.
+
+For this case, ACPI video driver does not need to do anything(actually,
+it doesn't even know this happened).
+
+ii) For some laptops, the press of the hotkey will not generate the
+    scancode, instead, firmware will notify the video device ACPI node
+    about the event. The event value is defined in the ACPI spec. ACPI
+    video driver will generate an key type input event according to the
+    notify value it received and send the event to user space through the
+    input device it created:
+
+	event		keycode
+	0x86		KEY_BRIGHTNESSUP
+	0x87		KEY_BRIGHTNESSDOWN
+	etc.
+
+so this would lead to the same effect as case i) now.
+
+Once user space tool receives this event, it can modify the backlight
+level through the sysfs interface.
+
+3 Change backlight level in the kernel
+
+This works for machines covered by case ii) in Section 2. Once the driver
+received a notification, it will set the backlight level accordingly. This does
+not affect the sending of event to user space, they are always sent to user
+space regardless of whether or not the video module controls the backlight level
+directly. This behaviour can be controlled through the brightness_switch_enabled
+module parameter as documented in kernel-parameters.txt. It is recommended to
+disable this behaviour once a GUI environment starts up and wants to have full
+control of the backlight level.
diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index 9f401350f502..67f733d6f848 100644
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -370,8 +370,10 @@ A: There is no clear spec defined way from ACPI that can give us that
    CPUs in MADT as hotpluggable CPUS.  In the case there are no disabled CPUS
    we assume 1/2 the number of CPUs currently present can be hotplugged.
 
-   Caveat: Today's ACPI MADT can only provide 256 entries since the apicid field
-   in MADT is only 8 bits.
+   Caveat: ACPI MADT can only provide 256 entries in systems with only ACPI 2.0c
+   or earlier ACPI version supported, because the apicid field in MADT is only
+   8 bits. From ACPI 3.0, this limitation was removed since the apicid field
+   was extended to 32 bits with x2APIC introduced.
 
 User Space Notification
 
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 2fe6e767b3d6..7f64e0f0258a 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3229,6 +3229,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	video=		[FB] Frame buffer configuration
 			See Documentation/fb/modedb.txt.
 
+	video.brightness_switch_enabled= [0,1]
+			If set to 1, on receiving an ACPI notify event
+			generated by hotkey, video driver will adjust brightness
+			level and then send out the event to user space through
+			the allocated input device; If set to 0, video driver
+			will only send out the event without touching backlight
+			brightness level.
+			default: 1
+
 	virtio_mmio.device=
 			[VMMIO] Memory mapped virtio (platform) device.
 
diff --git a/Documentation/power/video_extension.txt b/Documentation/power/video_extension.txt
deleted file mode 100644
index b2f9b1598ac2..000000000000
--- a/Documentation/power/video_extension.txt
+++ /dev/null
@@ -1,37 +0,0 @@
-ACPI video extensions
-~~~~~~~~~~~~~~~~~~~~~
-
-This driver implement the ACPI Extensions For Display Adapters for
-integrated graphics devices on motherboard, as specified in ACPI 2.0
-Specification, Appendix B, allowing to perform some basic control like
-defining the video POST device, retrieving EDID information or to
-setup a video output, etc.  Note that this is an ref. implementation
-only.  It may or may not work for your integrated video device.
-
-Interfaces exposed to userland through /proc/acpi/video:
-
-VGA/info : display the supported video bus device capability like Video ROM, CRT/LCD/TV.
-VGA/ROM :  Used to get a copy of the display devices' ROM data (up to 4k).
-VGA/POST_info : Used to determine what options are implemented.
-VGA/POST : Used to get/set POST device.
-VGA/DOS : Used to get/set ownership of output switching:
-	Please refer ACPI spec B.4.1 _DOS
-VGA/CRT : CRT output
-VGA/LCD : LCD output
-VGA/TVO : TV output
-VGA/*/brightness : Used to get/set brightness of output device
-
-Notify event through /proc/acpi/event:
-
-#define ACPI_VIDEO_NOTIFY_SWITCH        0x80
-#define ACPI_VIDEO_NOTIFY_PROBE         0x81
-#define ACPI_VIDEO_NOTIFY_CYCLE         0x82
-#define ACPI_VIDEO_NOTIFY_NEXT_OUTPUT   0x83
-#define ACPI_VIDEO_NOTIFY_PREV_OUTPUT   0x84
-
-#define ACPI_VIDEO_NOTIFY_CYCLE_BRIGHTNESS      0x82
-#define ACPI_VIDEO_NOTIFY_INC_BRIGHTNESS        0x83
-#define ACPI_VIDEO_NOTIFY_DEC_BRIGHTNESS        0x84
-#define ACPI_VIDEO_NOTIFY_ZERO_BRIGHTNESS       0x85
-#define ACPI_VIDEO_NOTIFY_DISPLAY_OFF           0x86
-
diff --git a/MAINTAINERS b/MAINTAINERS
index 5be702cc8449..95911afa818f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -242,6 +242,8 @@ F:	drivers/acpi/
 F:	drivers/pnp/pnpacpi/
 F:	include/linux/acpi.h
 F:	include/acpi/
+F:	Documentation/acpi
+F:	Documentation/ABI/testing/sysfs-bus-acpi
 
 ACPI FAN DRIVER
 M:	Zhang Rui <rui.zhang@intel.com>