Input: add driver for FT5x06 based EDT displays

This is a driver for the EDT "Polytouch" family of touch controllers
based on the FocalTech FT5x06 line of chips.

Signed-off-by: Simon Budig <simon.budig@kernelconcepts.de>
Reviewed-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/input/edt-ft5x06.txt

@@ -0,0 +1,54 @@
+EDT ft5x06 based Polytouch devices
+----------------------------------
+
+The edt-ft5x06 driver is useful for the EDT "Polytouch" family of capacitive
+touch screens. Note that it is *not* suitable for other devices based on the
+focaltec ft5x06 devices, since they contain vendor-specific firmware. In
+particular this driver is not suitable for the Nook tablet.
+
+It has been tested with the following devices:
+  * EP0350M06
+  * EP0430M06
+  * EP0570M06
+  * EP0700M06
+
+The driver allows configuration of the touch screen via a set of sysfs files:
+
+/sys/class/input/eventX/device/device/threshold:
+    allows setting the "click"-threshold in the range from 20 to 80.
+
+/sys/class/input/eventX/device/device/gain:
+    allows setting the sensitivity in the range from 0 to 31. Note that
+    lower values indicate higher sensitivity.
+
+/sys/class/input/eventX/device/device/offset:
+    allows setting the edge compensation in the range from 0 to 31.
+
+/sys/class/input/eventX/device/device/report_rate:
+    allows setting the report rate in the range from 3 to 14.
+
+
+For debugging purposes the driver provides a few files in the debug
+filesystem (if available in the kernel). In /sys/kernel/debug/edt_ft5x06
+you'll find the following files:
+
+num_x, num_y:
+    (readonly) contains the number of sensor fields in X- and
+    Y-direction.
+
+mode:
+    allows switching the sensor between "factory mode" and "operation
+    mode" by writing "1" or "0" to it. In factory mode (1) it is
+    possible to get the raw data from the sensor. Note that in factory
+    mode regular events don't get delivered and the options described
+    above are unavailable.
+
+raw_data:
+    contains num_x * num_y big endian 16 bit values describing the raw
+    values for each sensor field. Note that each read() call on this
+    files triggers a new readout. It is recommended to provide a buffer
+    big enough to contain num_x * num_y * 2 bytes.
+
+Note that reading raw_data gives a I/O error when the device is not in factory
+mode. The same happens when reading/writing to the parameter files when the
+device is not in regular operation mode.