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 buses 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>.