suse man page for user_regset_active_fn

USER_REGSET_ACTIVE_F(9) 					   Machine State					   USER_REGSET_ACTIVE_F(9)

NAME
       user_regset_active_fn - type of active function in struct user_regset

SYNOPSIS
       typedef int user_regset_active_fn(struct task_struct * target, const struct user_regset * regset);

ARGUMENTS
       target
	   thread being examined

       regset
	   regset being examined

DESCRIPTION
       Return -ENODEV if not available on the hardware found. Return 0 if no interesting state in this thread. Return >0 number of size units of
       interesting state. Any get call fetching state beyond that number will see the default initialization state for this data, so a caller that
       knows what the default state is need not copy it all out. This call is optional; the pointer is NULL if there is no inexpensive check to
       yield a value < n.

Kernel Hackers Manual 2.6.					     July 2010						   USER_REGSET_ACTIVE_F(9)