Re: [Xen-devel] Re: [RFC PATCH 03/35] Add Xen interface header files

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 9 May 2006, at 21:40, Hollis Blanchard wrote:

> The scatter/gather lists are still needed, but they are hidden inside
> copy_to/from_guest().
>
> If you change "unsigned long *" to an integer-based guest_handle_t, you
> will lose type-checking when accessing it, and I believe that's why you
> created these macros. I'm not particularly worried about type-checking,
> so I'd be happy to see them go, as long as we still have typedefs
It's tempting. We can still ensure that those fields are only accessed 
via the correct functions by making the typedef structural. All we lose 
is the ability to discriminate between different types of handles. 
Still, it is nice to get some kind of hint from the handle definition 
the type of the thing that it references. I wouldn't trust a comment 
beside each guest-handle field to be kept up to date. Having the type 
passed to the guest_handle() macro does get us some self documentation.
However, macro or no macro: even reducing it to just a typedef won't 
get past some of the guys on lkml without a fight.
 -- Keir


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