linux-kernel - Re: [PATCH] dmaengine: pl08x: fix conversioin for generic unmap data

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Date:	Thu, 28 Nov 2013 11:30:03 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	Olof Johansson <olof@...om.net>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dmaengine: pl08x: fix conversioin for generic unmap
 data

On Wed, Nov 27, 2013 at 11:55:01AM -0800, Dan Williams wrote:
> On Tue, Nov 26, 2013 at 8:53 PM, Olof Johansson <olof@...om.net> wrote:
> > commit d38a8c622a1b ('dmaengine: prepare for generic 'unmap' data')
> > added a generic unmap call but used the wrong argument for it. Fix it.
> >
> > Fixes: d38a8c622a1b ('dmaengine: prepare for generic 'unmap' data')
> > Signed-off-by: Olof Johansson <olof@...om.net>
> > ---
> >
> > I can't actually tell what the intent of d38a8cc622a1b and how mappings
> > are expected to be managed, but it's obviously passing the wrong thing
> > in here so it seems like the appropriate fix.
> >
> 
> For most dma-slave usage cases the client is explicitly handling the
> lifetime of the dma mappings.  It's primarily the mem-to-mem usage
> cases that rely on the dma driver to do the unmapping when the
> transaction is complete.  dma_descriptor_unmap() is a common
> implementation rather than requiring each driver to implement it
> uniquely.  Longer term we can require all clients to handle their
> mapping lifetimes and remove the responsibility from the individual
> drivers completely.
I think that would make sense and also remove any abuiguity on who does the
mapping in different usages..

~Vinod
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