The mode parameter type was changed in the callback function devnode in
struct device_type.

commit 2c9ede55ecec58099b72e4bb8eab719f32f72c31
Author: Al Viro <viro@zeniv.linux.org.uk>
Date:   Sat Jul 23 20:24:48 2011 -0400

    switch device_get_devnode() and ->devnode() to umode_t *