Re: Univeral Protocol Driver (using UNDI) in Linux

From: Daniel Rodrick
Date: Thu Aug 10 2006 - 04:15:45 EST

Hello Alan,

First things first. Tons of thanks for a mail FULLY LOADED with useful
information. I'm still to digest it all, but really thanks.

>> >
>> > I'm sure having a single driver for all the NICs is a feature cool
>> > enough to die for. Yes, it might have drawbacks like just pointed out
>> > by Peter, but surely a "single driver for all NIC" feature could prove
>> > to be great in some systems.
>> >
> Hi ... so there seem to be no technical feasibily issues, just
> reliabliy / ugly design issues? So one can still go ahead and write a
> Universal Protocol Driver that can work with all (PXE compatible)
> NICs?

With help from the Etherboot Project, I've recently implemented such a
driver for Etherboot 5.4. It currently supports PIO NICs (e.g. cards
that use in*/out* to interface with CPU). It's currently available in a
branch, and will be merged into the trunk by the Etherboot project. It
works reliably with QEMU + PXELINUX, with the virtual ne2k-pci NIC.

Umm ... pardon me if I am wrong, but I think you implemented a "UNDI
Driver" (i.e. the code that provides implementation of UNDI API, and
often resides in the NIC ROM) . I'm looking forward to write a
"Universal Protocol Driver" (i.e. the code that will be a linux kernel
module and will, use the UNDI API provided by your UNDI driver).

But nevertheless your information has been *VERY* helpful ...

At minimum, one needs to be able to probe for !PXE presence, which means
you need to map in 0-1MB of physical memory. The PXE stack's memory also
needs to be mapped in. My UNDI driver relies on a kernel module, generic
across all NICs, to accomplish these by mapping in the !PXE probe area
and PXE memory in a user process.

I'm pretty newbie to PXE, but I I think !PXE structure is used to find
out the location & size of PXE & UNDI runtime routines, by UNIVERSAL
PROTOCOL DRIVERS. Is my understanding wrong?

Also, I think that UNDI driver routine will need not call PXE routines
(TFTP / DHCP etc) as UNDI routines would be at a lower level providing
access to the bare bones hardware. Is this correct?


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