Re: etherboot-3.2

[markus@infoscape.com]

Paulo Jorge Veloso Lameirinhas writes:
 > > It depends on whether someone has the time to write a driver. Obviously
 > > that person has to have the hardware too. Etherboot is a volunteer
 > > effort.
 > >
 > What Kind of HardWare Is Needed ... Besides the Nic(s) ...

You really do not need much more than the NICs (and at least two
PC's); although it does make things easier if you can get access to an
EPROM burner or (preferably) have a FlashCard. If the latter is not an
option, you can always boot from floppy or use a second network card
(e.g. an old NE2k) to bootstrap the image for the new card. This is
the approach that I have taken and it gives you very fast turn-around
times.

 > > No, the structure of Linux and Etherboot are quite different for
 > > reasons too long to explain here.
 > >
 > Where Can I Get That Kind of Information ...

The structure of the etherboot drivers is very simple. You have to
write a function that probes for the card and (if successful) returns
pointers to a few other functions. These include code to reset and to
disable the card. And two functions for datatransmission; one for
sending and the other one for polling. The use of interrupts is
discouraged because at boottime you cannot fully rely on the machine
to be properly initialized. When writing the driver you should try to
make it as fault tolerant as possible; even if this means sacrificing
some performance. Drivers have to be fully capable of autoprobing for
all parameters. This sounds a lot more difficult than it really is.

Linux drivers are a lot more complex because they usually try to
achieve optimal performance. This means that they make use of
interrupts and DMA transfers where available; but they also require a
properly initialized system and might require the user to do some
extra configuration. When converting a driver from Linux to etherboot
you can usually remove about 50% of the code which is way to
sophisticated for a BOOT prom. The most difficult part is usually
converting the driver from interrupt driven mode to a polling
driver. This part will probably require you to have access to
technical documentation for the card.

On the whole, if you have access to decent documentation and you can
base your work on an existing (Linux) driver, expect to spend between
two and five days to convert the driver. You might have to spend a few 
more days for fine-tuning.

 > > Have you joined the Netboot mailing list? There are experts in that
 > > mailing list who know more than I do.
 > >
 > How Can I Joined To That Mailing List ...

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Markus

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Markus Gutschke                         Internet: markus@infoscape.com
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