IOKit Network Subclass Guidance
IOKit Network Subclass Guidance
- Subject: IOKit Network Subclass Guidance
- From: Michael Cashwell <email@hidden>
- Date: Tue, 10 Jun 2003 14:54:05 -0400
Greetings all,
I've been tasked with developing an IOKit driver for an ATM PCI card.
I've worked on NKEs before and have done some preliminary development
on another Ethernet driver that never got very far.
My basic question at present is where in IOKit to subclass. If I were
developing a full blown ATM driver (with support for ATM routing and
all manner of other ATM-specific interfaces and protocols) I expect I'd
want to subclass IONetworkController. But this project is more limited.
It only needs to be a LANE (LAN Emulation) Client and perhaps someday
to support MPOA (Multiprotocol over ATM; essentially adding a next-hop
resolution protocol that allows for direct ATM connections across
routers).
The key element here is that the OS's view of a LANE Client ATM
interface is exactly the same as an 802.x-based Ethernet interface:
6-octet MAC addresses, roughly 1500-octet MTU, unicast, multicast, and
broadcast support, and so forth. This makes me think I should subclass
IOEthernetController.
There will be a private interface (via a specialized ATM-aware User
Client I expect) between my driver and a userland daemon which runs a
LANE ARP state machine. But the rest of the OS would just see a
published nub that looks, smells and tastes like a normal Ethernet
interface.
At least, that's what I'm thinking presently. Does this seem like the
right approach? And if so, which superclass would be better? My hunch
is IOEthernetController but I'm concerned about subclassing what is
already a concrete class. If I have to fight it at every step then its
parent is probably a better choice. For example, I want the interface
name(s) (like those listed by ifconfig) to be "lec#" (standing for LANE
Client) not "en#".
Lastly, how might IONetworkInterface and IOEthernetInterface figure
into this? Do these classes abstract things like topology (bus, point
to point, ring) and medium (UTP, fiber) or is it more than that?
Thanks for any input.
-Mike
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