Return the driver-specific state of
. The softc is automatically allocated and zeroed when the device is attached. The softc is also initialized and present when a device is probed, but is subject to caveats as described in
. The size of the allocation is determined by the device's
information used to define the driver. The softc typically encapsulates the state of this instance of the device.
Driver writers are discouraged from using their own softc management mechanisms. Driver writers should not copy such mechanisms found in drivers in the tree that predate this function.