Re: lnc(4) driver ported from freebsd (le(4))

["Bill Marquette" <bill.marquette@xxxxxxxxx>]

On 7/2/06, Sepherosa Ziehau <sepherosa@xxxxxxxxx> wrote:
> On 7/2/06, Bill Marquette <bill.marquette@xxxxxxxxx> wrote:
> > I was interested in learning something about the kernel, so figured
> > I'd take a crack at porting the le(4) driver that FreeBSD brought in
> > from NetBSD - the ultimate goal is to bring pcn(4) from NetBSD over -
> > the combination of the two drivers appears to be better than the
> > existing lnc(4)/pcn(4) that Dragonfly has today (at least for VMWare)
>
> VMware only uses lnc(4)
>
> > and supports VLANs which the existing lnc(4) doesn't appear to (maybe
> > I missed something).  As Dragonfly already has a le(4) driver and this
> > was really a replacement for the existing lnc(4), I changed the driver
> > name to lnc (functions and some defines are a little goofy right now
> > because of it - looking for a little direction there).
> >
> > If there's interest, I'm looking for a little feedback on the port.  I
> > know there's still some cleanup to do (and a man page update!), but
> > more importantly:
> >
> > I borrowed the lock code from aac(4) - I'm not sure it's the "right
> > way" to do things as it's the only driver that seems to use lock(9)
> > functions - but it was the easiest one to use to see Dragonfly vs
> > FreeBSD differences.
> > I ifdef'd out FreeBSD-isms (I still have some cleaning to do there) -
> > I'm not sure how that's treat in the Dragonfly tree, I only see a few
> > instances of that in the network drivers, maybe that code should just
> > go?
>
> No extra lock is needed, all of the functions in "ifnet" struct are
> called with ifp->if_serializer held, that means most functions in
> network driver are protected by ifp->if_serializer (which you have
> passed to bus_setup_intr() too).  So you can safely nuke most of the
> LE_(UN)LOCK stuffs, except for "suspend", "resume", "shutdown" and
> "detach", LE_(UN)LOCK should be changed to
> lwkt_serializer_{enter,exit}() there (you can take a look to xl(4) for
> example).  Special care should be taken for "detach": you should held
> serializer for driver functions (e.g. lance_stop()) and
> bus_teardown_intr(), while serializer should be released before
> calling ether_ifdetach(), you can take a look at pcn_detach() for
> example.  Since no callouts are used, there is nothing to worry about
> the callout callback functions, otherwise the callback functions
> should hold serializer too.
>
> > FreeBSD has BUS_PROBE_LOW_PRIORITY to set bus priorities so drivers
> > can pre-empt other drivers, I didn't see anything akin to that in
> > Dragonfly (and sadly hardcoded the value - this needs to be cleaned up
> > still).  The old driver defined LNC_PROBE_PRIORITY to -1, is that the
> > "correct way" ? :)
>
> Less than 0 is OK.
>
>
> Thank you for the submission!!
> If you can change the LE_(UN)LOCK stuffs, we can call for testing and
> bring it into base soon.

OK, updated patch at http://www.pfsense.org/~billm/dfly/lnc.patch
it includes the LOCK -> serializer fixes, some crit_enter/exit fixes
that I think were needed, defining the bus probe priority (-100), and
removing FreeBSD specific code.

I've still got the man page to update, but I think/hope this is
correct enough to go in after the freeze for 1.6 is lifted.

--Bill