From: arnd@arndb.de (Arnd Bergmann)
Date: Wed, 24 Oct 2012 12:24:06 +0000
Subject: [PATCH 2/2] arm: mvebu: Add hardware I/O Coherency support
In-Reply-To: <5087D6B8.10209@free-electrons.com>
References: <1351065841-18654-1-git-send-email-gregory.clement@free-electrons.com>
 <5087D574.4030503@free-electrons.com> <5087D6B8.10209@free-electrons.com>
Message-ID: <201210241224.06791.arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Wednesday 24 October 2012, Gregory CLEMENT wrote:
> On 10/24/2012 01:48 PM, Gregory CLEMENT wrote:
> > On 10/24/2012 01:36 PM, Arnd Bergmann wrote:
> >>
> >> I think it would be cleaner to statically define the operations in a constant
> >> structure and point directly to the functions you need. If necessary, use
> >> multiple structures.
> > 
> > My problem was that these functions are not exposed, only arm_dma_op and
> > arm_coherent_dma_ops are exported.
> > Or do you think about something like this:
>
> struct dma_map_ops *dma_ops = {
>         .alloc                  = arm_coherent_dma_ops.arm_coherent_dma_alloc,
>         .free                   = arm_coherent_dma_ops.arm_coherent_dma_free,
>         .mmap                   = arm_coherent_dma_ops.arm_dma_mmap,
>         .get_sgtable            = arm_coherent_dma_ops.arm_dma_get_sgtable,
>         .map_sg                 = arm_coherent_dma_ops.arm_dma_map_sg,
>         .set_dma_mask           = arm_coherent_dma_ops.arm_dma_set_mask,
>         .map_page               = armada_xp_dma_map_page,
>         .unmap_page             = armada_xp_dma_unmap_page,
>         .unmap_sg               = arm_dma_ops.unmap_sg,
>         .sync_single_for_cpu    = armada_xp_dma_sync,
>         .sync_single_for_device = armada_xp_dma_sync,
>         .sync_sg_for_cpu        = arm_dma_ops.sync_sg_for_cpu,
>         .sync_sg_for_device     = arm_dma_ops.sync_sg_for_device,
> };

No, I was thinking of making the underlying functions globally visible
and have extern declarations in a header file so you can access them
directly.

Generally speaking, when you run into a problem with common code, your
first approach should be to fix the common code before you try to work
around it.

	Arnd