Re: The i2o Bus: A Conspiracy Against Free Software?
On Thu, 17 Jul 1997, Mr Stuart Lamble wrote:
> I've had a brief look at http://www.i2osig.org/background.html, and it would
> _appear_ that the only necessity for Linux would be to provide an interface
> layer between the operating system and the I2O device. Unfortunately, I can't
> tell how this would work in a manner independant of the OS (from the device
> driver point of view).
The driver actually runs on a separate processor and OS! An i960 CPU
that runs along side the main CPU. The only thing linux would require is
the abillity to interface with that i960. There is supposed to be detailed
standard on how to make the code running on the i960 do things. Ie if you
wanted to control any scsi controller you send this message <blank>
> _IF_ the object code for these drivers is usable on any OS (which is what
> I read as being the aim of the standard), _AND_ Linux can get that interface
> layer implemented under the GPL, there may not be anything to worry about.
> However, those two ifs are very big ones.
Nono, object code is provided for the i960, not the x86's. It is optimized
to convert the standard messages into something your SCSI controller can
handle fast. Presumably the SCSI controller has a rom with this code in it
or something, I don't know those details.
The problem for linux comes that the interfacing message format (they had
a nice picture of how this worked) may be under NDA/Restriction. I forget
if I looked to see if the license terms were geared at the i960 code or
the whole thing.
The really sad part is if this uses the WindRiver stuff and what Cygnus
says about Windriver using GCC is true then they are using free code to
produce the product they are trying to prevent free software from
using!
I belive the whole idea is basically that most PC os's disable interrupts
for a long time, don't know about linux, but I do know NT is in the
hundred microsecond range! That seriously kills performance. Probably also
gives a big boost to multiprocessor things.. donno
(AFAIK this I20 stuff is for pretty much anything, SCSI is just a handy
example) I'll dig up the articles tomorrow and post any relavent facts
from them. Might also want to check http://www.eetimes.com, I think this
was on the front page at one time.
Jason
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