NAME

       BUS_READ_IVAR, BUS_WRITE_IVAR — manipulate bus-specific device instance variables

SYNOPSIS

       #include <sys/param.h>
       #include <sys/bus.h>

       int
       BUS_READ_IVAR(device_t dev, device_t child, int index, uintptr_t *result);

       int
       BUS_WRITE_IVAR(device_t dev, device_t child, int index, uintptr_t value);

DESCRIPTION

       These  two  methods  manage a bus specific set of instance variables of a child device.  The intention is
       that each different type of bus defines a set of appropriate instance variables (such as ports  and  irqs
       for ISA bus etc.)

       This  information  could be given to the child device as a struct but that makes it hard for a bus to add
       or remove variables without forcing an edit and recompile for all drivers which may not be  possible  for
       vendor supplied binary drivers.

RETURN VALUES

       Zero is returned on success, otherwise an appropriate error is returned.

SEE ALSO

       device(9), driver(9)

AUTHORS

       This manual page was written by Doug Rabson.

Debian                                            June 16, 1998                                 BUS_READ_IVAR(9)