dyoung@pobox.com wrote:

> > XXX1: I don't know why original FreeBSD driver checks
> >       if a number of free TX descriptors is more than two, not zero.
> 
> It is because a typical mbuf chain is about three segments long, so you
> need at least three descriptors unless you are willing to copy three
> segments into one.

Each TX descriptor on vge(4) has a fragment list to handle chains
like ex(4) or epic(4), so one descriptor is enough to send a packet,
I suppose.
---
Izumi Tsutsui