DEVICE_ADD_CHILD(9)

NAME
device_add_child, device_add_child_ordered - add a new device as a child of an existing device

SYNOPSIS
#include <sys/param.h>
#include <sys/bus.h>
device_t
device_add_child(device_t dev, const char *name, int unit);
device_t
device_add_child_ordered(device_t dev, int order, const char *name, int unit);

DESCRIPTION
Create a new child device of dev. The name and unit arguments specify the name and unit number of the device. If the name is unknown then the caller should pass NULL. If the unit is unknown then the caller should pass -1 and the system will choose the next available unit number.

The name of the device is used to determine which drivers might be appropriate for the device. If a name is specified then only drivers of that name are probed. If no name is given then all drivers for the owning bus are probed.

This allows busses which can uniquely identify device instances (such as PCI) to allow each driver to check each device instance for a match. For busses which rely on supplied probe hints where only one driver can have a chance of probing the device, the driver name should be specified as the device name.

Normally unit numbers will be chosen automatically by the system and a unit number of -1 should be given. When a specific unit number is desired (e.g. for wiring a particular piece of hardware to a pre-configured unit number), that unit should be passed. If the specified unit number is already allocated, a new unit will be allocated and a diagnostic message printed.

If the devices attached to a bus must be probed in a specific order (e.g. for the ISA bus some devices are sensitive to failed probe attempts of unrelated drivers and therefore must be probed first), the order argument of device_add_child_ordered() should be used to specify a partial ordering. The new device will be added before any existing device with a greater order. If device_add_child() is used, then the new child will be added as if its order was zero.

RETURN VALUES
The new device if successful, NULL otherwise.

SEE ALSO
BUS_ADD_CHILD(9), device(9)

AUTHORS
This man page was written by Doug Rabson.