Re: [Xen-devel] [PATCH] make protocol specific usage of shared sring explicit

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Thu, 2010-07-01 at 10:58 +0100, Jan Beulich wrote:
> >>> On 01.07.10 at 11:22, Ian Campbell <ian.campbell@xxxxxxxxxx> wrote:
> > --- a/xen/include/public/io/ring.h  Wed Jun 30 22:12:54 2010 +0100
> > +++ b/xen/include/public/io/ring.h  Thu Jul 01 10:20:07 2010 +0100
> > @@ -103,8 +103,16 @@
> >  struct __name##_sring {                                                 \
> >      RING_IDX req_prod, req_event;                                       \
> >      RING_IDX rsp_prod, rsp_event;                                       \
> > -    uint8_t  netfront_smartpoll_active;                                 \
> > -    uint8_t  pad[47];                                                   \
> > +    union {                                                             \
> > +        struct {                                                        \
> > +            uint8_t smartpoll_active;                                   \
> > +        } netif;                                                        \
> > +        struct {                                                        \
> > +            uint8_t msg;                                                \
> > +        } tapif_user;                                                   \
> > +        uint8_t pvt_pad[4];                                             \
> > +    } private;                                                          \
> > +    uint8_t pad[44];                                                    \
> 
> Since this is source incompatible for consumers anyway, wouldn't
> it be better to rename the new pad[] to e.g. _pad[], so that builds
> of unchanged consumers fail instead of producing runtime
> incompatible code?

Yes, that's a good idea. I'll follow up with a patch to use __pad (I
think the single _ namespace is reserved for libc or some such)

Ian.


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