linux-kernel - Re: [PATCHv4] DMAEngine: Define interleaved transfer request api

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Message-ID: <1318334185.1546.344.camel@vkoul-udesk3>
Date:	Tue, 11 Oct 2011 17:26:25 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Jassi Brar <jaswinder.singh@...aro.org>
Cc:	"Williams, Dan J" <dan.j.williams@...el.com>,
	Russell King <rmk@....linux.org.uk>,
	Barry Song <21cnbao@...il.com>, linux-kernel@...r.kernel.org,
	DL-SHA-WorkGroupLinux <workgroup.linux@....com>,
	Dave Jiang <dave.jiang@...el.com>
Subject: Re: [PATCHv4] DMAEngine: Define interleaved transfer request api

On Mon, 2011-10-10 at 21:58 +0530, Jassi Brar wrote:
> On 10 October 2011 21:32, Vinod Koul <vinod.koul@...el.com> wrote:
> > On Mon, 2011-10-10 at 16:46 +0530, Jassi Brar wrote:
> >> On 10 October 2011 16:15, Vinod Koul <vinod.koul@...el.com> wrote:
> >> >
> >> > But I am fine if we find a common ground and merge the two where dmac
> >> > can cleanly identify direction and mode it is operating.
> >> >
> >> The client would set the xfer_direction and dmac would interpret as
> >>
> >> enum xfer_direction {
> >>      MEM_TO_MEM,   ->  Async/Memcpy mode
> >>      MEM_TO_DEV,    ->  Slave mode & From Memory to Device
> >>      DEV_TO_MEM,    ->  Slave mode & From Device to Memory
> >>      DEV_TO_DEV,     ->  Slave mode & From Device to Device
> >> }
> >>
> >> How could it get any cleaner?
> > Consider the case of a dmac driver which supports interleaved dma as
> > well as memcpy and slave
> > It needs to interpret dma_data_direction for later cases and
> > xfer_direction for former ones.
> dma_data_direction is the mapping attribute of a buffer and is not meant to
> tell type of source and destination of a transfer.
> xfer_direction is meant for that purpose.
> So I'd rather convert device_prep_dma_cyclic and device_prep_slave_sg
> to use xfer_direction.
If the conversion id done for all drivers, then it should be fine...

-- 
~Vinod

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