device_mapcreates a new memory manager for device and returns a port to it in pager. The memory manager is usable as a memory object in a
vm_mapcall. The call is device dependent.
The protection for the memory object is specified by prot. The memory object starts at offset within the device and extends size bytes. unmap is currently unused.
The function returns
D_SUCCESSif some data was successfully written and
D_NO_SUCH_DEVICEif device does not denote a device port or the device is dead or not completely open.