IEEE 1394 Unit Filter Driver Development Concepts (Windows CE 5.0)
Include the optional unit filter driver (AVC_UNIT) module to export functionality from your product through an AV/C subunit.
An AV/C subunit that exports functionality to other devices on the IEEE 1394 bus is called a virtual subunit. The unit filter driver acts as both a central repository and an intermediary for AV/C units. The AV/C Digital Interface Command Set General Specification contains the definitive definition and explanation of what constitutes a unit.
An AV/C compatible device on the bus contains an AV/C unit. Conceptual structures within the device that serve different purposes may be AV/C subunits. The unit manages details such as the power state of the device, which subunits it contains, and coordination over the association of serial bus plugs with subunit plugs.
When external devices send AV/C commands to query or request manipulation of specific plugs, the external device communicates with the unit filter driver. When a virtual subunit driver and its serial bus plugs are exposed to other devices on the bus, the virtual subunit driver has to coordinate with the unit filter driver.
WDM enumerates virtual subunit drivers as subordinates of the AV/C driver. The IEEE 1394 streaming filter driver is inserted between the virtual subunit driver and AV/C automatically as a lower filter driver definition. For more information, see IEEE 1394 Streaming Filter Drivers.
See Also
IEEE 1394 Unit Filter Driver Architecture | IEEE 1394 Unit Filter Driver Registration | IEEE 1394 Unit Filter Driver Plug Allocation | IEEE 1394 Unit Filter Driver Plug Management | Serial Bus and Subunit Plug Association | IEEE 1394 Unit Filter Driver Destination Selection | IEEE 1394 Unit Filter Driver Streaming
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