netbsd man page for nullop

NULLOP(9)						   BSD Kernel Developer's Manual						 NULLOP(9)

NAME
     nullop -- dummy functions

SYNOPSIS
     #include <sys/systm.h>

     int
     nullop(void *v);

     void
     voidop(void);

     int
     enodev(void);

     int
     enxio(void);

     int
     enoioctl(void);

     int
     enosys(void);

     int
     eopnotsupp(void);

DESCRIPTION
     The nullop() function provides a generic ``null operation''.  It always returns the value 0.  The voidop() function takes no arguments and
     does nothing.

     The enodev(), enxio(), enoioctl(), enosys(), and eopnotsupp() functions always fail, returning ENODEV, ENXIO, ENOTTY, ENOSYS, and EOPNOTSUPP,
     respectively.

EXAMPLES
     The following example demonstrates a case where nullop() may be useful:

	   uint64_t xc;

	   ...

	   xc = xc_broadcast(0, (xcfunc_t)nullop, NULL, NULL);
	   xc_wait(xc);

BSD
								   July 25, 2010							       BSD