BSP Developer's Guide

H
Implementing a MUX-Based Network Interface Driver
you need to know the context in which the entry point executes. Thus, you need to
know the following:
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The task that makes the calls that actually load and start your driver.
The task that typically registers the interrupt handler for your driver.
The task that uses your driver to do most of the processing on a packet.
H.2.1 Launching Your Driver
At system startup, VxWorks spawns the task tUsrRoot to handle the following:
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Initializing the network task’s job queue.
Spawning tNetTask to process items on the network task’s job queue.
Calling muxDevLoad( ) to load your network driver.
Calling muxDevStart( ) to start your driver.
Loading Your Driver into the MUX
To load your network driver, tUsrRoot calls muxDevLoad( ). As input to the call,
tUsrRoot specifies your driver’s endLoad( ) entry point. Internally, the
muxDevLoad( ) call executes the specified endLoad( ) entry point. This
endLoad( ) entry point is analogous to the xxattach( ) entry point, the only public
entry point into the 4.3 BSD style drivers.
The endLoad( ) routine handles any device-specific initialization and returns an
END_OBJ structure. Your endLoad( ) must populate most of this structure (see,
Providing Network Device Abstraction: END_OBJ, p.283). This includes providing a
pointer to a NET_FUNCS structure populated with function pointers to your
driver’s entry points for handling sends, receives, and so on.
After control returns from endLoad( ) to muxDevLoad( ), the MUX completes the
END_OBJ structure (by giving it a pointer to a function your driver can use to pass
packets up to the MUX). The MUX then adds the returned END_OBJ to a linked list
of END_OBJ structures. This list maintains the state of all the currently active
network devices on the system. After control returns from muxDevLoad( ), your
driver is loaded and ready to use.
H
Registering Your Driver’s Interrupt Routine
To register your driver’s interrupt handler, you must call sysIntConnect( ). The
most typical place to make this call is in your driver’s endStart( ) entry point.
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