From: Arnd Bergmann <arnd@arndb.de>
To: Gregory CLEMENT <gregory.clement@free-electrons.com>
Subject: Re: [PATCH 2/2] arm: mvebu: Add hardware I/O Coherency support
Date: Wed, 24 Oct 2012 12:24:06 +0000
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Cc: Lior Amsalem <alior@marvell.com>, Andrew Lunn <andrew@lunn.ch>,
        Ike Pan <ike.pan@canonical.com>, Nadav Haklai <nadavh@marvell.com>,
        Ian Molton <ian.molton@codethink.co.uk>,
        David Marlin <dmarlin@redhat.com>,
        Yehuda Yitschak <yehuday@marvell.com>,
        Jani Monoses <jani.monoses@canonical.com>,
        Russell King <linux@arm.linux.org.uk>,
        Tawfik Bayouk <tawfik@marvell.com>,
        Dan Frazier <dann.frazier@canonical.com>,
        "Eran Ben-Avi" <benavi@marvell.com>,
        Leif Lindholm <leif.lindholm@arm.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
        Jason Cooper <jason@lakedaemon.net>, Jon Masters <jcm@redhat.com>,
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        linux-arm-kernel@lists.infradead.org,
        Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
        Chris Van Hoof <vanhoof@canonical.com>,
        Nicolas Pitre <nico@fluxnic.net>, linux-kernel@vger.kernel.org,
        Maen Suleiman <maen@marvell.com>, Shadi Ammouri <shadi@marvell.com>,
        Olof Johansson <olof@lixom.net>
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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
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