Re: [PATCH] vhost: change the vhost library to a common framework which can support more VIRTIO devices

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Tue, Sep 13, 2016 at 03:24:53PM +0200, Thomas Monjalon wrote:
> 2016-09-13 20:58, Yuanhan Liu:
> > rte_virtio_net.h is the header file will be exported for applications.
> > Every change there would mean either an API or ABI breakage. Thus, we
> > should try to avoid touching it. Don't even to say you added yet another
> > header file, rte_virtio_dev.h.
> > 
> > I confess that the rte_virtio_net.h filename isn't that right: it sticks
> > to virtio-net so tightly. We may could rename it to rte_vhost.h, but I
> > doubt it's worthwhile: as said, it breaks the API.
> > 
> > The fortunate thing about this file is that, the context is actually not
> > sticking to virtio-net too much. I mean, all the APIs are using the "vid",
> > which is just a number. Well, except the virtio_net_device_ops() structure,
> > which also should be renamed to vhost_device_ops(). Besides that, the
> > three ops, "new_device", "destroy_device" and "vring_state_changed", are
> > actually not limited to virtio-net device.
> > 
> > That is to say, we could have two options here:
> > 
> > - rename the header file and the structure properly, to not limited to
> >   virtio-net
> > 
> > - live with it, let it be a legacy issue, and document it at somewhere,
> >   say, "due to history reason, that virtio-net is the first one supported
> >   in DPDK, we kept the header filename as rte_virtio_net.h, but not ..."
> > 
> > I personally would prefer the later one, which saves us from breaking
> > applications again. I don't have strong objection to the first one though.
> > 
> > Thomas, any comments?
> 
> I don't think keeping broken names for historical reasons is a good
> long term maintenance.

Good point.

> It could be a FIXME comment that we would fix when we have other reasons
> to break the API.
> However, in this case, it is easy to keep the compatibility, I think,
> by including rte_virtio.h in rte_virtio_net.h.

Nice trick!

> Note: renames can also generally be managed with symlinks.
> 
> I also don't really understand why this file name is rte_virtio_net.h and
> not rte_vhost_net.h.

No idea. It's just named so since the beginning. Also I missed this file
while doing the ABI/API refactoring, otherwise, it would be no pain at
this stage.

	--yliu