Add the rt linux 4.1.3-rt3 as base

Import the rt linux 4.1.3-rt3 as OPNFV kvm base.

It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and
the base is:

commit 0917f823c59692d751951bf5ea699a2d1e2f26a2
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date:   Sat Jul 25 12:13:34 2015 +0200

    Prepare v4.1.3-rt3

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

We lose all the git history this way and it's not good. We
should apply another opnfv project repo in future.

Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>

1 files changed, 123 insertions, 0 deletions

diff --git a/kernel/Documentation/rfkill.txt b/kernel/Documentation/rfkill.txt
new file mode 100644
index 000000000..2ee6ef9a6
--- /dev/null
+++ b/kernel/Documentation/rfkill.txt
@@ -0,0 +1,123 @@
+rfkill - RF kill switch support
+===============================
+
+1. Introduction
+2. Implementation details
+3. Kernel API
+4. Userspace support
+
+
+1. Introduction
+
+The rfkill subsystem provides a generic interface to disabling any radio
+transmitter in the system. When a transmitter is blocked, it shall not
+radiate any power.
+
+The subsystem also provides the ability to react on button presses and
+disable all transmitters of a certain type (or all). This is intended for
+situations where transmitters need to be turned off, for example on
+aircraft.
+
+The rfkill subsystem has a concept of "hard" and "soft" block, which
+differ little in their meaning (block == transmitters off) but rather in
+whether they can be changed or not:
+ - hard block: read-only radio block that cannot be overridden by software
+ - soft block: writable radio block (need not be readable) that is set by
+               the system software.
+
+The rfkill subsystem has two parameters, rfkill.default_state and
+rfkill.master_switch_mode, which are documented in kernel-parameters.txt.
+
+
+2. Implementation details
+
+The rfkill subsystem is composed of three main components:
+ * the rfkill core,
+ * the deprecated rfkill-input module (an input layer handler, being
+   replaced by userspace policy code) and
+ * the rfkill drivers.
+
+The rfkill core provides API for kernel drivers to register their radio
+transmitter with the kernel, methods for turning it on and off and, letting
+the system know about hardware-disabled states that may be implemented on
+the device.
+
+The rfkill core code also notifies userspace of state changes, and provides
+ways for userspace to query the current states. See the "Userspace support"
+section below.
+
+When the device is hard-blocked (either by a call to rfkill_set_hw_state()
+or from query_hw_block) set_block() will be invoked for additional software
+block, but drivers can ignore the method call since they can use the return
+value of the function rfkill_set_hw_state() to sync the software state
+instead of keeping track of calls to set_block(). In fact, drivers should
+use the return value of rfkill_set_hw_state() unless the hardware actually
+keeps track of soft and hard block separately.
+
+
+3. Kernel API
+
+
+Drivers for radio transmitters normally implement an rfkill driver.
+
+Platform drivers might implement input devices if the rfkill button is just
+that, a button. If that button influences the hardware then you need to
+implement an rfkill driver instead. This also applies if the platform provides
+a way to turn on/off the transmitter(s).
+
+For some platforms, it is possible that the hardware state changes during
+suspend/hibernation, in which case it will be necessary to update the rfkill
+core with the current state is at resume time.
+
+To create an rfkill driver, driver's Kconfig needs to have
+
+	depends on RFKILL || !RFKILL
+
+to ensure the driver cannot be built-in when rfkill is modular. The !RFKILL
+case allows the driver to be built when rfkill is not configured, which
+case all rfkill API can still be used but will be provided by static inlines
+which compile to almost nothing.
+
+Calling rfkill_set_hw_state() when a state change happens is required from
+rfkill drivers that control devices that can be hard-blocked unless they also
+assign the poll_hw_block() callback (then the rfkill core will poll the
+device). Don't do this unless you cannot get the event in any other way.
+
+
+
+5. Userspace support
+
+The recommended userspace interface to use is /dev/rfkill, which is a misc
+character device that allows userspace to obtain and set the state of rfkill
+devices and sets of devices. It also notifies userspace about device addition
+and removal. The API is a simple read/write API that is defined in
+linux/rfkill.h, with one ioctl that allows turning off the deprecated input
+handler in the kernel for the transition period.
+
+Except for the one ioctl, communication with the kernel is done via read()
+and write() of instances of 'struct rfkill_event'. In this structure, the
+soft and hard block are properly separated (unlike sysfs, see below) and
+userspace is able to get a consistent snapshot of all rfkill devices in the
+system. Also, it is possible to switch all rfkill drivers (or all drivers of
+a specified type) into a state which also updates the default state for
+hotplugged devices.
+
+After an application opens /dev/rfkill, it can read the current state of all
+devices. Changes can be either obtained by either polling the descriptor for
+hotplug or state change events or by listening for uevents emitted by the
+rfkill core framework.
+
+Additionally, each rfkill device is registered in sysfs and emits uevents.
+
+rfkill devices issue uevents (with an action of "change"), with the following
+environment variables set:
+
+RFKILL_NAME
+RFKILL_STATE
+RFKILL_TYPE
+
+The contents of these variables corresponds to the "name", "state" and
+"type" sysfs files explained above.
+
+
+For further details consult Documentation/ABI/stable/sysfs-class-rfkill.