add a new device as a child of an existing
, const char
Create a new child device of dev
arguments specify the name and unit
number of the device. If the name is unknown then the caller should pass
. If the unit is unknown then the
caller should pass
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. In
any event, only the name of the device is stored so that one may safely
unload/load a driver bound to that name.
This allows buses which can uniquely identify device instances (such as PCI) to
allow each driver to check each device instance for a match. For buses 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
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
() should be used
to specify a partial ordering. The new device will be added before any
existing device with a greater order. If
() is used, then the new
child will be added as if its order was zero.
When adding a device in the context of
routine should be used to ensure that the device has not already been added to
the tree. Because the device name and
are associated at probe time (not
child addition time), previous instances of the driver (say in a module that
was later unloaded) may have already added the instance. Authors of bus
drivers must likewise be careful when adding children when they are loaded and
unloaded to avoid duplication of children devices.
When adding a child to another device node, such as in an identify routine, use
and add the proper bus-specific data to the new child.
() does not call
The new device if successful, NULL otherwise.
This manual page was written by Doug