> Of cause I want to use the kernel's infrastructure for queueing of
> packages and stuff. But for the ease of coding I want to have the
> protocol implemented in a library in user-space. I want the
> kernel-driver to just receive and transmit the packages. How can I
> implement the hooks for passing the packages up to user-land and
> process them further?
> Untill now I used the ethernet setup stuff. But since my card uses
> (kind of) RS485-serial protocol I will have to change that, too.
I'm also intending to at some point to implement a fieldbus protocol (Profibus)
that runs over RS485. If we can design a simple way for user-space libraries to
send and receive whole packets over RS485 media, then it could be used by many
such projects.
I was intending to do it as a line discipline, although the 'normal' line
discipline behaviour isn't good enough for synchronous operation. However, the
N_HDLC line discipline which turned up in 2.2.x recently may well prove to be
an extremely good model for what we want.
Basically, the Profibus definition of a 'packet' is a sequence of bits which
is preceded and followed by 33 idle bits (3 characters @ _8n1_). That's about
the only information that needs to be passed down to that layer - the amount
of time to leave as a 'packet gap'. What about your system?
What hardware are you using for RS485 communication? I'm looking at the
Comtrol RocketPort 485 cards, but haven't yet been approved to actually go
ahead and spend real money on the project.
<PLUG>
For people interested in Profibus on Linux, we already have some intelligent
IO cards from Applicom (www.applicom-int.com) working under Linux in a
production environment. Let me know if you want more information.
</PLUG>
---- ---- ----
David Woodhouse David.Woodhouse@mvhi.com Office: (+44) 1223 810302
Project Leader, Process Information Systems Mobile: (+44) 976 658355
Axiom (Cambridge) Ltd., Swaffham Bulbeck, Cambridge, CB5 0NA, UK.
finger dwmw2@ferret.lmh.ox.ac.uk for PGP key.
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