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

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> 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?

Jan


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