Re: PATCH: VLAN support for 3c59x/3c90x

[Willy Tarreau <willy@w.ods.org>]

Hi Jeff,

On Sat, Jul 31, 2004 at 05:34:41AM -0400, Jeff Garzik wrote:
> Willy Tarreau wrote:
> >  - many (all ?) other drivers already have an MTU parameter, and many
> 
> s/many/almost none/

Ok, sorry, I've just checked, they are 6. But I incidentely used the feature
on 2 of them (dl2k and starfire). But more drivers still have the
'static int mtu=1500' preceeded by a comment stating "allow the user to change
the mtu". Why is it not a #define then, if nobody can change it anymore ?

> For VLAN support you definitely want to let the user increase the size 
> above 1500, and for that you need ->change_mtu

I agree, but my point was that adding MODULE_PARM was only a one liner and
would have done the job too. But since everyone prefers a change_mtu(), I'll
do it.

Jeff, do you know the absolute hardware limit on the tulip ? I've seen the
limitation to PKT_BUF_SZ (1536), but I don't know for example if the
hardware stores the FCS in the buffer or not, nor if the IP headers risk
being aligned or not (which would consume 2 more bytes).
Or does 1536 - 14 (ethernet) - 2 (iphdr alignment) - 4 (FCS) = 1516 seem a
reasonable conservative higher bound ?

Cheers,
Willy