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System Management Guide: Communications and Networks

Implementing the GDLC Interface

Each DLC device manager is a standard /dev entry operating in the kernel as a multiplexed device manager for a specified protocol. For an adapter not in use by DLC, each open subroutine to a DLC device manager creates a kernel process. An open subroutine is also issued to the target adapter device handler. If needed, issue additional open subroutines for multiple DLC adapter ports of the same protocol. Any open subroutine targeting the same port does not create additional kernel processes, but links the open subroutine with the existing process. There is always one kernel process for each port in use.

The internal structure of a DLC device manager has the same basic structure as a kernel device handler, except that a kernel process replaces the interrupt handler in asynchronous events. The read, write, I/O control, and select blocks function as shown in the "Standard Kernel Device Manager" figure.

Figure 7-3. Standard Kernel Device Manager. This illustration shows the internal structure of a DLC device manager. This structure consists of a Write, I/O Control, Read, Select, and Interrupt Handler. The Device Manager receives information from the user where it is passed to the various areas before it is passed on to the Device Handler.

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