src/sys/[arch]/[arch] - Kernel code for a specific machine architecture resides in this directory. For example, the i386 architecture, or the SPARC64 architecture.

src/sys/dev/[bus] - device support for a specific [bus] resides in this directory.

src/sys/dev/pci - PCI bus support code resides in this directory.

src/sys/[isa|pci] - PCI/ISA device drivers reside in this directory. The PCI/ISA bus support code used to exist in this directory in FreeBSD version 4.0.

devclass_t - This is a type definition of a pointer to a struct devclass.

device_method_t - This is the same as kobj_method_t (see src/sys/kobj.h).

device_t - This is a type definition of a pointer to a struct device. device_t represents a device in the system. It is a kernel object. See src/sys/sys/bus_private.h for implementation details.

driver_t - This is a type definition which references struct driver. The driver struct is a class of the device kernel object; it also holds data private to the driver.

	  struct driver {
		KOBJ_CLASS_FIELDS;
		void	*priv;			/* driver private data */
	  };

A device_state_t type, which is an enumeration, device_state. It contains the possible states of a Newbus device before and after the autoconfiguration process.

	  /*
	   * src/sys/sys/bus.h
	   */
	  typedef enum device_state {
		DS_NOTPRESENT,	/* not probed or probe failed */
		DS_ALIVE,		/* probe succeeded */
		DS_ATTACHED,	/* attach method called */
		DS_BUSY			/* device is open */
	  } device_state_t;