i-8042: check for status

Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
linear: allow mixing inputs and setpoints

Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
linear: fix zero division check

Signed-off-by: Sergei Ianovich <ynvich@gmail.com>