Re: Source code compatibility in Stable series????

["Petr Vandrovec" <VANDROVE@vc.cvut.cz>]

On 11 May 01 at 12:03, Andi Kleen wrote:
> On Fri, May 11, 2001 at 02:56:35AM -0700, David S. Miller wrote:
> I guess it would be possible to add a HAVE_ZEROCOPY to skbuff.h to make
> it a bit easier for single source drivers.
> 
> --- include/linux/skbuff.h-o    Wed May  9 12:36:44 2001
> +++ include/linux/skbuff.h  Fri May 11 12:12:43 2001
> @@ -29,6 +29,7 @@
>  #define HAVE_ALLOC_SKB     /* For the drivers to know */
>  #define HAVE_ALIGNABLE_SKB /* Ditto 8)        */
>  #define SLAB_SKB       /* Slabified skbuffs       */
> +#define HAVE_ZEROCOPY      /* Zerocopy stack */ 

When I was updating VMware's vmnet, I decided to use

#ifdef skb_shinfo

This gives you maximal backward compatibility, as all public zerocopy
patches contain this macro. Only thing is that Dave has to remember
that when he turns skb_shinfo into inline function, an identity #define have
to be added.

Just my opinion - as you cannot add HAVE_ZEROCOPY to all already existing
and installed kernels.
                                                Petr Vandrovec
                                                vandrove@vc.cvut.cz