Re: [virtio-comment] [PATCH 1/1] ccw: ccw payload description

[Thomas Huth <thuth@linux.vnet.ibm.com>]

On Mon, 20 Jan 2014 11:17:17 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Mon, Jan 20, 2014 at 02:28:00PM +1030, Rusty Russell wrote:
> > Cornelia Huck <cornelia.huck@de.ibm.com> writes:
> > > Move the ccw payload description to tables, instead of using
> > > C structures with gcc extensions or textual descriptions.
> > 
> > I think it's horrible.
> > 
> > Almost everyone reading this will understand C.  And they can cut and
> > paste the code from the spec into their implementation, which helps
> > everyone.
> > 
> > We'll just have to live with the lack of padding, and let's try not to
> > add any more packed-requiring structures.  If we deprecate
> > virtio-balloon, the rest will be contained in CCW.
> > 
> > Cheers,
> > Rusty.
> 
> For CCW, how about my idea of adding optional padding explicitly?
> In the compatibility section, we can explicitly specify the
> the length.
> Drivers can use offsetof(padding) and avoid packed attribute.

Adding compiler/language-dependend work-arounds (either the packed
attribute or the manual padding) to a generic standard specification
sounds really wrong to me ... but if Rusty really does not like the
tables, I also do not have a better idea here.

 Thomas