Input: document struct input_absinfo

Add documentation for struct input_absinfo that is used in EVIOCGABS
and EVIOCSABS ioctl and specify units of measure used for reporting
resolution for an axis.

Acked-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

include/linux/input.h

@@ -47,6 +47,25 @@ struct input_id {
 	__u16 version;
 };
 
+/**
+ * struct input_absinfo - used by EVIOCGABS/EVIOCSABS ioctls
+ * @value: latest reported value for the axis.
+ * @minimum: specifies minimum value for the axis.
+ * @maximum: specifies maximum value for the axis.
+ * @fuzz: specifies fuzz value that is used to filter noise from
+ *	the event stream.
+ * @flat: values that are within this value will be discarded by
+ *	joydev interface and reported as 0 instead.
+ * @resolution: specifies resolution for the values reported for
+ *	the axis.
+ *
+ * Note that input core does not clamp reported values to the
+ * [minimum, maximum] limits, such task is left to userspace.
+ *
+ * Resolution for main axes (ABS_X, ABS_Y, ABS_Z) is reported in
+ * units per millimeter (units/mm), resolution for rotational axes
+ * (ABS_RX, ABS_RY, ABS_RZ) is reported in units per radian.
+ */
 struct input_absinfo {
 	__s32 value;
 	__s32 minimum;
@@ -1134,7 +1153,7 @@ struct input_mt_slot {
  *	of tracked contacts
  * @mtsize: number of MT slots the device uses
  * @slot: MT slot currently being transmitted
- * @absinfo: array of &struct absinfo elements holding information
+ * @absinfo: array of &struct input_absinfo elements holding information
  *	about absolute axes (current value, min, max, flat, fuzz,
  *	resolution)
  * @key: reflects current state of device's keys/buttons