[Linux driver]A Little about put_user & __put_user

  put_user and __put_user used to write the datum to user space Function Declaration of put_user => put_user(datum, ptr)           Function Declaration of __put_user => __put_user(datum, ptr) When single values are to be transferred, put_user/ __put_user should be called instead copy_to_user . Reason behind this is        these functions(put_user/__put_user ) are relatively fast.   Difference