Re: RFC: Evolution of the em driver

On 10/30/07, gnn_at_freebsd.org <gnn_at_freebsd.org> wrote:
> At Mon, 29 Oct 2007 10:45:17 -0700,
> Jack Vogel wrote:
> >
> > I have an important decision to make and I thought rather than just make
> > it and spring it on you I'd present the issues and see what opinions were.
> >
> > Our newer hardware uses new features that, more and more, require
> > parallel code paths in the driver. For instance, the 82575 (Zoar) uses
> > what are called 'advanced descriptors', this means different TX path.
> > The 7.0 em driver has this support in it, it just uses a function pointer
> > to handle it.
> >
> > When I add in multiqueue/RSS support it will add even more code
> > that functions this way.
> >
> > What the Linux team did was to split the newer code into a standalone
> > driver, they call it 'igb'. I had originally resisted doing this, but with
> > the development I have been working on the past month I am starting
> > to wonder if it might not be best to follow them.
> >
> > I see 3 possibilities and I'd like feedback, which would you prefer if
> > you have a preference and why.
> >
> > First, keep the driver as is and just live with multiple code paths
> > and features, possibly #ifdef'ed as they appear.
> >
> > Second, split the driver as Linux has into em and igb. The added
> > question then is how to split it, Linux made the line the use of
> > advanced descriptors, so Zoar and after, but I could also see a
> > case for having everything PCI-E/MSI capable being in the new
> > driver.
> >
> > Third, sort of a half-way approach, split up code but not the
> > driver, in other words offer different source files that can be
> > compiled into the driver, so you could have the one big jumbo
> > driver with all in there, or one that will only work with a subset
> > of adapters. This one would probably be the most work, because
> > its a new approach.
>
> As you're the main maintainer it's your choice.  Whatever is easiest
> for you and gives us the most readable code.

Thanks, I know its my choice, I was just looking for opinions about
the options I had to chose from :)

I think I've had enough feedback to decide, I think the seperate
driver is the direction. I need to give some thought to where to
make the split.

Thanks for everyone's feedback.

Jack