Re: fwip(4) carrier detection

[David Young <dyoung%pobox.com@localhost>]

On Wed, Oct 14, 2009 at 07:57:33PM +0200, Quentin Garnier wrote:
> On Tue, Oct 13, 2009 at 09:19:00PM +0100, Roy Marples wrote:
> > Hi List
> > 
> > fwip(4) lacks carrier detection that most other drivers offer.
> > How hard would it be to add?
> > 
> > Or another solution for me would be to rely on SIOCGIFMEDIA working down 
> > the 
> > interface is down. This seems to work for bge(4) - should this generally be 
> > the case?
> 
> What does carrier detection mean in the context of fwip(4)?  What in
> your opinion should happen for a host that has more than one firewire
> port and only one controller?
> 
> You have to keep in mind fwip(4) is not Ethernet.

IIUC, ports belonging to the same controller form a "broadcast" network,
that is, devices on port A are addressable by devices on port B, and
vice versa, for any two ports A or B.  In other words, the FireWire
controller acts analogously to an ethernet hub/switch for its ports.
In that case, if there is no "live" device attached to any port, the
appropriate media status is 'no carrier'.  If there is a live device on
any single port, however, the media status should be 'active'.

I don't know if there is any way to detect the status of any single
port.  I *do* think that you can enumerate the nodes on the FireWire
bus.  If there is just one node, the local host, 'no carrier' seems
right, and if there are two or more nodes, then 'active'.

Dave

-- 
David Young             OJC Technologies
dyoung%ojctech.com@localhost      Urbana, IL * (217) 278-3933