I/O Request Processing Operation Flow

[This topic applies to UMDF 1.x.]

All I/O operations occur in the context of a file object (that is, all I/O operations occur between calls that an application makes to the Microsoft Win32 CreateFile and CloseHandle functions). I/O operations are calls that an application makes to, for example, the Win32 ReadFileEx, WriteFileEx, and DeviceIoControl functions.

The following topics show the flow of operations that occur to and from UMDF drivers as a user I/O transaction begins, processes, and ends in a single device stack and in a double device stack:

Operation Flow with Single Device Stack

Operation Flow with Double Device Stack

Note   All I/O that is initiated by applications is routed through kernel mode as shown in the figures in the Architecture of the UMDF section, even though the figures in the I/O Request Processing Operation Flow section do not show this situation.



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