linux-kernel - Re: Dmaengine query

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Message-ID: <AANLkTikA0YefhGQb9V2e9Ub5W21cTy3pY66Rn1VDpX9Q@mail.gmail.com>
Date:	Mon, 24 May 2010 02:01:34 +0200
From:	Linus Walleij <linus.ml.walleij@...il.com>
To:	rd bairva <rbairva@...il.com>
Cc:	Dan Williams <dan.j.williams@...el.com>,
	linux-arm-kernel@...ts.arm.linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: Dmaengine query

2010/4/19 rd bairva <rbairva@...il.com>:

>    My DMA controller supports device to device DMA transfers and we
> need it in some of our drivers. Existing DMA engine framework doesn't
> have support for device to device transfers.
>
> Do you have any plans for device to device support in DMA engine?
>
> Can you suggest me some other suggestion for doing this?

Extend the DMA engine with the stuff you need and propose nice
patches, provide them along with a driver that make use of this
feature.

What about a signature like this:

struct dma_async_tx_descriptor *(*device_prep_slave2slave)(
                struct dma_chan *chan1, struct dma_chan *chan2,
                enum dma_data_direction direction,
                unsigned long flags);

You'd have to add some semantics comment saying that
DMA_TO_DEVICE means chan1->chan2 and
DMA_FROM_DEVICE means chan1<-chan2.

Could be a bit of hacking but how hard can it be?

Yours,
Linus Walleij
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