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Subject: Re: EMM: Fixup return value handling of emm_notify()
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Christoph Lameter <clameter@sgi.com>
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Date: Thu, 03 Apr 2008 12:40:46 +0200
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On Wed, 2008-04-02 at 14:33 -0700, Christoph Lameter wrote:
> On Wed, 2 Apr 2008, Andrea Arcangeli wrote:
> 
> > but anyway it's silly to be hardwired to such an interface that worst
> > of all requires switch statements instead of proper pointer to
> > functions and a fixed set of parameters and retval semantics for all
> > methods.
> 
> The EMM API with a single callback is the simplest approach at this point. 
> A common callback for all operations allows the driver to implement common 
> entry and exit code as seen in XPMem.

It seems to me that common code can be shared using functions? No need
to stuff everything into a single function. We have method vectors all
over the kernel, we could do a_ops as a single callback too, but we
dont.

FWIW I prefer separate methods.

> I guess we can complicate this more by switching to a different API or 
> adding additional emm_xxx() callback if need be but I really want to have 
> a strong case for why this would be needed. There is the danger of 
> adding frills with special callbacks in this and that situation that could 
> make the notifier complicated and specific to a certain usage scenario. 
> 
> Having this generic simple interface will hopefully avoid such things.
> 
>