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

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Message-ID: <20160420185844.GQ1990@wotan.suse.de>
Date:	Wed, 20 Apr 2016 20:58:44 +0200
From:	"Luis R. Rodriguez" <mcgrof@...nel.org>
To:	Chris Wilson <chris@...is-wilson.co.uk>
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>,
	"Luis R . Rodriguez" <mcgrof@...nel.org>,
	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 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.

Other than that possible API optimization:

Reviewed-by: Luis R. Rodriguez <mcgrof@...nel.org>

  Luis