On Tue, Jan 28, 2014 at 11:17:57AM +0000, Russell King - ARM Linux wrote:

On Tue, Jan 28, 2014 at 10:16:53AM +0100, Arnd Bergmann wrote:

quoted

On Tuesday 28 January 2014 10:05:35 Lars-Peter Clausen wrote:

quoted

Why does the direction needs to be specified in specifier? I see two
options, either the direction per is fixed in hardware. In that case the DMA
controller node should describe which channel is which direction. Or the
direction is not fixed in hardware and can be changed at runtime in which
case it should be set on a per descriptor basis.

Normally the direction is implied by dmaengine_slave_config().

No.  The direction argument in there is deprecated - we've been talking
about removing it for some time.

DMA engine drivers should store all parameters of the configuration, and
then select the appropriate ones when preparing a transfer (which itself
involves a direction.)

Right all the prep_ calls for slave cases have explcit direction argument so
sending it using slave config makes no sense. So will remove it after the merge
window closes and fix :)

--
~Vinod

Not doing this implies that if you have a half-duplex device, you have to
repeatedly issue a dmaengine_slave_config() call, a prepare call, and a
submit call to the DMA engine code for every segment you want to transfer.
We don't need that kind of DMA engine specific behaviour in DMA engine
users.

-- 
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Estimate before purchase was "up to 13.2Mbit".
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