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

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Date:	Mon, 10 Oct 2011 21:58:43 +0530
From:	Jassi Brar <jaswinder.singh@...aro.org>
To:	Vinod Koul <vinod.koul@...el.com>
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 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.
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