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, 79 insertions, 0 deletions

diff --git a/kernel/drivers/staging/iio/Documentation/device.txt b/kernel/drivers/staging/iio/Documentation/device.txt
new file mode 100644
index 000000000..8be32e5a0
--- /dev/null
+++ b/kernel/drivers/staging/iio/Documentation/device.txt
@@ -0,0 +1,79 @@
+IIO Device drivers
+
+This is not intended to provide a comprehensive guide to writing an
+IIO device driver.  For further information see the drivers within the
+subsystem.
+
+The crucial structure for device drivers in iio is iio_dev.
+
+First allocate one using:
+
+struct iio_dev *indio_dev = iio_device_alloc(sizeof(struct chip_state));
+where chip_state is a structure of local state data for this instance of
+the chip.
+
+That data can be accessed using iio_priv(struct iio_dev *).
+
+Then fill in the following:
+
+- indio_dev->dev.parent
+	Struct device associated with the underlying hardware.
+- indio_dev->name
+	Name of the device being driven - made available as the name
+	attribute in sysfs.
+
+- indio_dev->info
+	pointer to a structure with elements that tend to be fixed for
+	large sets of different parts supported by a given driver.
+	This contains:
+	* info->driver_module:
+		Set to THIS_MODULE. Used to ensure correct ownership
+		of various resources allocate by the core.
+	* info->event_attrs:
+		Attributes used to enable / disable hardware events.
+	* info->attrs:
+		General device attributes. Typically used for the weird
+		and the wonderful bits not covered by the channel specification.
+	* info->read_raw:
+		Raw data reading function. Used for both raw channel access
+		and for associate parameters such as offsets and scales.
+	* info->write_raw:
+		Raw value writing function. Used for writable device values such
+		as DAC values and calibbias.
+	* info->read_event_config:
+		Typically only set if there are some interrupt lines.  This
+		is used to read if an on sensor event detector is enabled.
+	* info->write_event_config:
+		Enable / disable an on sensor event detector.
+	* info->read_event_value:
+		Read value associated with on sensor event detectors. Note that
+		the meaning of the returned value is dependent on the event
+		type.
+	* info->write_event_value:
+		Write the value associated with on sensor event detectors. E.g.
+		a threshold above which an interrupt occurs.  Note that the
+		meaning of the value to be set is event type dependant.
+
+- indio_dev->modes:
+	Specify whether direct access and / or ring buffer access is supported.
+- indio_dev->buffer:
+	An optional associated buffer.
+- indio_dev->pollfunc:
+	Poll function related elements. This controls what occurs when a trigger
+	to which this device is attached sends an event.
+- indio_dev->channels:
+	Specification of device channels. Most attributes etc. are built
+	from this spec.
+- indio_dev->num_channels:
+	How many channels are there?
+
+Once these are set up, a call to iio_device_register(indio_dev)
+will register the device with the iio core.
+
+Worth noting here is that, if a ring buffer is to be used, it can be
+allocated prior to registering the device with the iio-core, but must
+be registered afterwards (otherwise the whole parentage of devices
+gets confused)
+
+On remove, iio_device_unregister(indio_dev) will remove the device from
+the core, and iio_device_free(indio_dev) will clean up.