Re: [PATCH 02/19] io-mapping: Specify mapping size for io_mapping_map_wc()

[Chris Wilson]

On Wed, Apr 20, 2016 at 08:58:44PM +0200, Luis R. Rodriguez wrote:
> On Wed, Apr 20, 2016 at 07:42:13PM +0100, Chris Wilson wrote:
> > The ioremap() hidden behind the io_mapping_map_wc() convenience helper
> > can be used for remapping multiple pages. Extend the helper so that
> > future callers can use it for larger ranges.
> > 
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> > Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> > Cc: David Airlie <airlied@xxxxxxxx>
> > Cc: Yishai Hadas <yishaih@xxxxxxxxxxxx>
> > Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
> > Cc: David Hildenbrand <dahi@xxxxxxxxxxxxxxxxxx>
> > Cc: Luis R. Rodriguez <mcgrof@xxxxxxxxxx>
> > Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > Cc: netdev@xxxxxxxxxxxxxxx
> > Cc: linux-rdma@xxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> 
> We have 2 callers today, in the future, can you envision
> this API getting more options? If so, in order to avoid the
> pain of collateral evolutions I can suggest a descriptor
> being passed with the required settings / options. This lets
> you evolve the API without needing to go in and modify
> old users. If you choose not to that's fine too, just
> figured I'd chime in with that as I've seen the pain
> with other APIs, and I'm putting an end to the needless
> set of collateral evolutions this way.

Do you have a good example in mind? I've one more patch to try and take
advantage of the io-mapping (that may or not be such a good idea in
practice) but I may as well see if I can make io_mapping more useful
when I do.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre