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.\" Copyright (c) 1998 Doug Rabson
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.Dd June 16, 1998
.Dt device_add_child 9
.Os FreeBSD
.Sh NAME
.Nm device_add_child ,
.Nm device_add_child_after
.Nd add a new device as a child of an existing device
.Sh SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <sys/bus.h>
.Ft int
.Fn bus_add_child "device_t dev" "const char *name" "int unit" "void *ivars"
.Ft int
.Fn bus_add_child_after "device_t dev" "device_t place" "const char *name" "int unit" "void *ivars"
.Sh DESCRIPTION
.Pp
Create a new child device of
.Fa dev .
The
.Fa name
and
.Fa unit
arguments specify the name and unit number of the device.
If the name is unknown then the caller should pass
.Dv NULL .
If the unit is unknown then the caller should pass 
.Dv -1
and the system will choose the next available unit number.
If there is any bus-specific data associated with the new child device 
(i.e. port numbers, irq settings etc.) then this should be supplied as 
the
.Fa ivars
argument.
.Pp
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.
.Pp
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 change of probing the device, the driver name should
specified as the device name.
.Pp
Normally unit numbers will be chosen automatically by the system and a 
unit number of
.Dv -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.
.Pp
If the devices attached to a bus must be probed in a specific order
(e.g. for ISA bus devices which are sensitive to failed probe attempts 
of unrelated drivers), the
.Fa place
argument of
.Xr device_add_child_after 9
should be used.  If
.Dv NULL
is passed, the new device will be added as the first child of
.Fa dev ,
otherwise it will be added immediately after
.Fa place
(which must be an existing child of
.Fa dev )
in the list of children.  If
.Xr device_add_child 9
is used, then the new child will be added at the end of the list.
.Sh RETURN VALUES
The new device if successful, NULL otherwise.
.Sh SEE ALSO
.Xr device 9
.Sh AUTHORS
This man page was written by
.An Doug Rabson .