linux-kernel - Re: [PATCH 2.6.24-rc1] fix sg_phys to use dma_addr

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Message-ID: <20071025075425.GD5053@kernel.dk>
Date:	Thu, 25 Oct 2007 09:54:25 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.24-rc1] fix sg_phys to use dma_addr_t

On Thu, Oct 25 2007, Hugh Dickins wrote:
> On Wed, 24 Oct 2007, Arjan van de Ven wrote:
> > > Signed-off-by: Hugh Dickins <hugh@...itas.com>
> > > ---
> > > Whether this is a complete patch, suitable for all architectures,
> > > I'm not sure: it builds, boots and runs correctly on the x86_32 box
> > > in question, but you'll be a lot wiser than me about using dma_addr_t
> > > for everyone.  (Seems a bit of a shame to include <asm/types.h> here,
> > > when I think all arches already get to include it one way or another,
> > > typically via asm/scatterlist.h; but I guess it's safest to repeat
> > > it.)
> > 
> > there is a problem with this... sg_phys doesn't return an actual *dma*
> > address.... at least not an address you can give to the device.
> > Using dma_addr_t is thus a bit misleading.....
> 
> True.  Perhaps sg_phys() should use its own sg_phys_addr_t, defined
> or typedefed to be the same as dma_addr_t.  But would this inline
> function then be the only place in the tree which uses that type?
> If so, then it'd probably be better just to let sg_phys() carry on
> using dma_addr_t, but insert a comment there to make your point.
> 
> But I'll leave it to Jens to fix up the patch appropriately: for
> all I know, there might be arches on which using dma_addr_t there
> actually does the wrong thing - I don't think so, but I know too
> little about it.

dma_addr_t would seem OK to me, given the lack of phys_addr_t.

-- 
Jens Axboe

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