Re: [PATCH v1 ib-next 2/3] IB/core: IB/core: Allow legacy verbs through extended interfaces

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On Tue, Nov 10, 2015 at 11:21:07AM -0700, Jason Gunthorpe wrote:
> On Tue, Nov 10, 2015 at 08:00:09PM +0200, Eli Cohen wrote:
> > When an extended verbs is an extension to a legacy verb, the original
> > functionality is preserved. Hence we do not require each hardware driver
> > to set the extended capability. This will allow to use the extended verb
> > in its simple form with drivers that do not support the extended
> > capability.
> 
> Can we please get rid of uverbs_cmd_mask and uverbs_ex_cmd_mask ?
> 
> The driver should set the function pointers it does not support to
> NULL. We don't need the bitmask because we already know the answer.
> 
> For performance, I recommend having the core replace the NULL op
> pointers from the driver with a stub that returns ENOTSUP, and then
> drop all the checking in the fast path.
>

Yes, we can do this but I think this should be the subject for another
patch, agree?

Regarding using stabs, it may be nice but I don't think performance is
the issue here. Most verbs implementations involve relatively long i/o
operations anyway so the gain will not be noticable.
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