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

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Message-ID: <CAJe_ZheapUSd5Wt5-1bi_cS1WvOjBsQ-sh5JXx1p1mH4Xb+hoQ@mail.gmail.com>
Date:	Tue, 11 Oct 2011 21:27:16 +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 11 October 2011 17:26, 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...
>
I already said that many days ago. Though I am not sure what blocks
this patch if that conversion is done separately (which would touch many
subsystems).
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