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BSP Developer's Guide

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G<br />

Upgrading 4.3 BSD<br />

Network Drivers<br />

G.1 Introduction<br />

This appendix describes two upgrade paths for 4.3 BSD network drivers. One path<br />

simply ports the 4.3 BSD network driver to the BSD 4.4 model. The other path<br />

upgrades the 4.3 BSD network driver to an END driver (described in<br />

H. Implementing a MUX-Based Network Interface Driver).<br />

Porting a network driver to the 4.4 BSD model should require only minimal<br />

changes to the code. In fact, porting some drivers has taken less than a day’s work.<br />

However, an older driver that does not already use a transmission startup routine<br />

can take longer to port.<br />

Porting a network driver to an END requires more extensive changes. However, it<br />

is worth the effort if the driver must handle the following:<br />

■<br />

■<br />

■<br />

■<br />

multicasting<br />

polled-mode Ethernet (necessary for WDB debugging of the kernel over a<br />

network, a mode that is several orders of magnitude faster than the serial link)<br />

zero-copy transmission<br />

support for network protocols other than IP<br />

NOTE: This chapter assumes that you are already familiar with BSD network<br />

device drivers. You should also have already read H. Implementing a MUX-Based<br />

Network Interface Driver.<br />

257

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