The Role of Driver Layers in Plug and Play

The WDM model of drivers is built upon structured layers of Physical Device Objects (PDOs) and Functional Device Objects (FDOs). Generally, a PDO exists for each physical piece of hardware attached to a bus and assumes the responsibility for low-level device control common to multiple functions realized by the hardware. An FDO exists for each logical or abstract function presented to higher-level software.

As an example, consider a physical disk drive and driver. It can be represented by a PDO that implements bus adapter functions (e.g., adapting an IDE disk bus to a PCI bus). Once the PDO for the disk bus adapter is realized, an FDO assumes responsibility for the functional operations of the disk itself. ...

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