BUS_READ_IVAR(9)

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 man page was written by Doug Rabson.