Search notes:

include/linux/input.h

Declarations of interesting functions in include/linux/input.h are, imho:

struct input_value

The input_value struct represents an input value: 
struct input_value {
  __u16 type;
  __u16 code;
  __s32 value;
}
Compare with struct input_event found in include/uapi/linux/input.h.

struct input_dev

The input_dev struct represents an input device.

See also

include/uapi/linux/input.h

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