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Message-ID: <292693080608100118rc910647l7a8bf95fbc2df26c@mail.gmail.com>
Date: Thu, 10 Aug 2006 13:48:14 +0530
From: "Daniel Rodrick" <daniel.rodrick@gmail.com>
To: "Alan Shieh" <ashieh@cs.cornell.edu>
Subject: Re: Univeral Protocol Driver (using UNDI) in Linux
Cc: "H. Peter Anvin" <hpa@zytor.com>,
       "Linux Newbie" <linux-newbie@vger.kernel.org>,
       kernelnewbies <kernelnewbies@nl.linux.org>, linux-net@vger.kernel.org,
       linux-kernel@vger.kernel.org
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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.
> >> >
[Snip]
> >
> > 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?

Thanks,

Dan
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