NAME
DEVICE_IDENTIFY - identify a device, register it
SYNOPSIS
#include <sys/param.h>
#include <sys/bus.h>
void
DEVICE_IDENTIFY(driver_t *driver, device_t parent);
DESCRIPTION
The identify function for a device is only needed for devices on busses
that cannot identify their children independently, e.g. the ISA bus. It
is used to recognize the device (usually done by accessing non-ambiguous
registers in the hardware) and to tell the kernel about it and thus
creating a new device instance.
BUS_ADD_CHILD(9) is used to register the device as a child of the bus.
The device’s resources (such as IRQ and I/O ports) are registered with
the kernel by calling bus_set_resource() for each resource (refer to
bus_set_resource(9) for more information).
Since the device tree and the device driver tree are disjoint, the
DEVICE_IDENTIFY() routine needs to take this into account. If you load
and unload your device driver that has the identify routine, the child
node has the potential for adding the same node multiple times unless
specific measure are taken to preclude that possibility.
EXAMPLES
The following pseudo-code shows an example of a function that probes for
a piece of hardware and registers it and its resource (an I/O port) with
the kernel.
void
foo_identify(driver_t *driver, device_t parent)
{
device_t child;
retrieve_device_information;
if (devices matches one of your supported devices &&
not already in device tree) {
child = BUS_ADD_CHILD(parent, 0, "foo", -1);
bus_set_resource(child, SYS_RES_IOPORT, 0, FOO_IOADDR, 1);
}
}
SEE ALSO
BUS_ADD_CHILD(9), bus_set_resource(9), device(9), device_add_child(9),
DEVICE_ATTACH(9), DEVICE_DETACH(9), DEVICE_PROBE(9), DEVICE_SHUTDOWN(9)
AUTHORS
This manual page was written by Alexander Langer 〈alex@FreeBSD.org〉.