Excellent job on the firewire support!
Hidetoshi Shimokawa
simokawa at sat.t.u-tokyo.ac.jp
Mon Jul 19 18:53:00 PDT 2004
At Sun, 18 Jul 2004 21:04:53 +0100,
Doug Rabson wrote:
> > It would be nice to remove my Comtrol Rocketport serial card, and the
> > 8 serial cables leading across the middle of the room to my shelf of
> > machines and replace it with one firewire cable leading to a firewire
> > hub. But, as a firewire newbie, I have some questions:
> >
> > 1) Is any firewire PCI adapter just as good as any other in terms of
> > performance, and FreeBSD support? (prices seem to range from $10
> > to $100)
>
> Any should do about as well as any other. I probably wouldn't want to
> spend more than ~$50 on one.
I got some bad report about Lucent chip(some Mac's have it)
but I haven't heard any other compatibility issue.
I think the price of the adapter doesn't matter but you may
have trouble with some bad cables. If have some problem,
use lower speed(S100) or change cables.
> >
> > 2) Is dcons usable after a panic (ie, DDB or KDB_TRACE)? Or is it
> > only usable for remote-gdb?
>
> Dcons provides two full duplex streams - one for console and one for
> gdb. You can use DDB on the console just like normal.
It's designed for such panic/debugging situation.
Actually, it's rather inefficient for usual situation
but the speed of FireWire hide the problem ;-)
> >
> > 3) Is dcons endian and pointer-size agonstic? Can I run consoles to
> > an amd64 and a powerpc box from an x86?
>
> I haven't actually tried that and I imagine that there might be issues
> here and there. Any problems are likely to be in the dconschat program
> but that should be pretty easy to fix since its entirely userland.
I should have no problem with 64bit arch and big endian.
I have tested with sparc64, powerpc and amd64.
> >
> > 4) Does the loader know about dcons? Eg, can I do "unload <ret> boot
> > kernel.test" using dcons?
>
> Actually thats the only downside of dcons. It doesn't cut in until the
> firewire controller attaches. It relies on the fact that the fwohci
> driver allows access to physical memory from any node on the bus
> (implemeted in hardware so you can examine the memory of a hung
> machine). The dconschat program uses this feature to access the dcons
> ring buffers in the target machine.
>
> I could imagine a dcons driver in the loader which just enabled physical
> access and used some kind of loader trick to hand off the ring buffers
> to the kernel dcons driver. It doesn't exist though - say nice things
You are right.
> to the author and he might find the time for it :-)
It is not enough :-< I lack the knowledge of BIOS/PCI(and ACPI?).
Once we can access the OHCI register via PCI in the loader,
the remaining part is relatively easy as you described.
I need some help for this part. I suppose that implementing dcons
in the loader is architecture dependent.
/\ Hidetoshi Shimokawa
\/ simokawa at sat.t.u-tokyo.ac.jp
PGP public key: http://www.sat.t.u-tokyo.ac.jp/~simokawa/pgp.html
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