linux-kernel - Re: [PATCHv3] DMAEngine: Define interleaved transfer request api

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Date:	Wed, 21 Sep 2011 12:21:43 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Jassi Brar <jaswinder.singh@...aro.org>
Cc:	dan.j.williams@...el.com, linux-kernel@...r.kernel.org,
	rmk@....linux.org.uk, 21cnbao@...il.com
Subject: Re: [PATCHv3] DMAEngine: Define interleaved transfer request api

On Wed, 2011-09-21 at 12:15 +0530, Jassi Brar wrote:
> On 21 September 2011 12:02, Vinod Koul <vinod.koul@...el.com> wrote:
> > On Tue, 2011-09-20 at 23:38 +0530, Jassi Brar wrote:
> >> On 20 September 2011 22:22, Vinod Koul <vinod.koul@...el.com> wrote:
> >> > Also for slave transfers, how do we infer direction?
> >> I already explained to Barry.  Here's it again.
> >>
> >> At any time, the dmac driver knows if the channel, on which the xfer is
> >> prepared/submitted is Slave or not.
> >>
> >> SLAVE Transfer
> >>    dmaxfer_template.src_inc  && !dmaxfer_template.dst_inc  => DMA_TO_DEVICE
> >>    !dmaxfer_template.src_inc  && dmaxfer_template.dst_inc  => DMA_FROM_DEVICE
> >>
> >> Mem->Mem Transfer
> >>    dmaxfer_template.src_inc  && !dmaxfer_template.dst_inc  => Meaningless
> >>    !dmaxfer_template.src_inc  && dmaxfer_template.dst_inc  => MemSet
> > Rather than each driver adding this logic with good chance of screwing
> > up, care to add this as helper in dmaengine.h
> >
> > Ideally, I would have preferred direction to be told explicitly, would
> > leave it you..
> >
> I repeat yet again :- "This api is common to Slave as well as Mem<->Mem"
> 
> Even if we have slave clients specify DMA_TO/FROM_DEVICE, what
> flag do you suggest Mem->Mem clients use ?
Would it be invalid in that case!!! Same as few ields in xt_template
would be for peripheral case..

-- 
~Vinod

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