Re: [rfc][patch] DRM initial function table support.

[Christoph Hellwig <hch@infradead.org>]

On Tue, Aug 31, 2004 at 09:07:11AM -0700, Ian Romanick wrote:
> I think the intention is to have default functions set in the 
> device-independent code and have the device-dependent code over-ride 
> them.  Since the defaults may not always be NULL, doing a struct like 
> that wouldn't really work.  I suppose we could have a struct and a 
> device-independent function that copies the non-NULL pointers from the 
> per-device struct.  Would that be better?

Don't copy them.  Just put

if (foo->ops->method1)
	foo->ops->method1(args);
else
	generic_method1(args);

in your code.  It's an additional branch, but you avoid the indirect
functioncalloverhead in exchange.