Re: USB NICs

[Marty Connor <mdc@thinguin.org>]

On 3/12/2000 11:01 PM Ken Yap ken@nlc.net.au wrote:
>Apparently they are starting to be supported in Linux kernel 2.3.
>Anybody played with these? I just wonder what would be needed to support
>network booting with USB NICs.

I have not played with any USB NICs yet, but I would imagine that if we 
consider the Universal Serial Bus to be just another kind of bus, with 
some controller chip, and some method to probe it, some method to address 
devices on it, and some method to transfer data to and from devices 
connected to it, one might imagine that support for USB (just like ISA 
and PCI) would have to be added to Etherboot.  The of course begs the 
questions, where would the boot media be for such a device?  How big 
would the code be to support USB?

I imagine looking at the Linux sources would be instructive;  I would 
suspect we would have a "usb.c" and "usb.h" files, and we would scan the 
bus somewhat like the pci code and isa code do.  If we ignore the 
possibility of someone trying to "hot swap" the usb adapter during 
etherboot, it could be possible.  The question I have is what the code 
size for this might be.

Next, there is the question of the kernel detecting and using a USB nic.

Let's imagine for a moment we have a laptop.  We use a floppy, because we 
don't have a place for a boot prom.  Suddenly, this looks a lot like the 
PCMCIA problem.  And didn't I hear that PCMCIA code is coming inside the 
kernel in 2.4 as well?   Could Firewire be too far off? 

In the USB case we have an ethernet card attached on a bus, and we have 
to find it, initialize it, and do IO with it long enough to get a kernel 
(and possibly RAM disk) loaded.  The we assume the kernel can handle what 
must be done.

OK, there's some thinking out loud to "stir the pot".  I'm hoping others 
with more experience will now jump in and comment :-)

Regards,

Marty

---
   Name: Martin D. Connor
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  Email: mdc@thinguin.org
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