netdev - Re: [PATCH 02/19] io-mapping: Specify mapping size for io_mapping_map

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Date:	Wed, 20 Apr 2016 20:14:32 +0100
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	"Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:	intel-gfx@...ts.freedesktop.org,
	Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
	Mika Kuoppala <mika.kuoppala@...ux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	Yishai Hadas <yishaih@...lanox.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	David Hildenbrand <dahi@...ux.vnet.ibm.com>,
	dri-devel@...ts.freedesktop.org, netdev@...r.kernel.org,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/19] io-mapping: Specify mapping size for
 io_mapping_map_wc()

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@...is-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
> > Cc: Daniel Vetter <daniel.vetter@...el.com>
> > Cc: Jani Nikula <jani.nikula@...ux.intel.com>
> > Cc: David Airlie <airlied@...ux.ie>
> > Cc: Yishai Hadas <yishaih@...lanox.com>
> > Cc: Dan Williams <dan.j.williams@...el.com>
> > Cc: Ingo Molnar <mingo@...nel.org>
> > Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
> > Cc: David Hildenbrand <dahi@...ux.vnet.ibm.com>
> > Cc: Luis R. Rodriguez <mcgrof@...nel.org>
> > Cc: intel-gfx@...ts.freedesktop.org
> > Cc: dri-devel@...ts.freedesktop.org
> > Cc: netdev@...r.kernel.org
> > Cc: linux-rdma@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> 
> 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