This patch adds support for the ultrasonic ranger srf04 of devantech.

This device is measuring the distance of objects in a range between 1 cm
and 3 meters and a theoretical resolution of 3 mm.

There are two GPIOs used:
  - trigger: set as output to the device when the measurement should start
  - echo: set by the device when the ultrasonic wave is sent out and reset
    when the echo is recognized; this needs to be an interrupt input

The time between setting and resetting the echo pin is the time the
waveform needed for one round trip. This time is recorded in the interrupt
handler.

The distance is calculated in the read function by using the ultrasonic
speed at 20 degrees celsius which is about 343 m/s.
Signed-off-by: NAndreas Klinger <ak@it-klinger.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

This is the IIO driver for devantech srf08 ultrasonic ranger which can be
used to measure the distances to an object.

The sensor supports I2C with some registers.

Supported Features include:
 - read the distance in ranging mode in centimeters
 - output of the driver is directly the read value
 - together with the scale the driver delivers the distance in meters
 - only the first echo of the nearest object is delivered
 - set sensitivity as analog value in the range of 0-31  means setting
   gain register on device
 - set range registers; userspace enters max. range in millimeters in
   43 mm steps

Features not supported by this driver:
 - ranging mode in inches or in microseconds
 - ANN mode
 - change I2C address through this driver
 - light sensor

The driver was added in the directory "proximity" of the iio subsystem and
the menu in den config is now called "Proximity and distance sensors"
Signed-off-by: NAndreas Klinger <ak@it-klinger.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

Add support for the PulsedLight LIDAR rangefinder sensor which allows
high speed (over 300Hz) distance measurements using Barker Coding within
40 meter range.

Support only tested on the "blue label" rev 2, but may work using low
sample frequencies on the original version.
Signed-off-by: NMatt Ranostay <mranostay@gmail.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

Supports buffering, IIO events and changing sampling frequency.

Datasheet available at:
http://www.semtech.com/images/datasheet/sx9500_ag.pdfSigned-off-by: NVlad Dogaru <vlad.dogaru@intel.com>
Reviewed-by: NHartmut Knaack <knaack.h@gmx.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

AS3935 chipset can detect lightning strikes and reports those back as
events and the estimated distance to the storm.
Signed-off-by: NMatt Ranostay <mranostay@gmail.com>
Reviewed-by: NMarek Vasut <marex@denx.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>