Bus Operations
A NetBSD system defines bus operations that are used to perform various
memory operations. Each bus type specifies its set of operations in a
bus_space struct generally referred to as a bus tag. This struct
specifies many types of memory operations; NetBSD defines many
generic operations, and any bus-specific operations can be
defined as needed. The vx115_io.c file defines a bus_space struct
called vx115_bs_tag, as well as several bus-specifc operations used in
this struct.
Each bus instance selects in its attach( ) function an appropriate bus
tag that defines the operations for that bus type. The bus then passes
the bus tag to its children during autoconfiguration. The children use
this tag in calls to the standard NetBSD memory functions such as
bus_space_map( ), bus_space_read_4( ), etc.
Comments/questions: jsevy@cs.drexel.edu
