[alsa-devel] [PATCH 19/19] ASoC: fsi: Add DMAEngine support

Lars-Peter Clausen lars at metafoo.de
Mon Feb 6 15:50:39 CET 2012

On 02/06/2012 03:46 PM, Vinod Koul wrote:
> On Mon, 2012-02-06 at 09:47 +0100, Lars-Peter Clausen wrote:
>> On 02/04/2012 07:40 PM, Vinod Koul wrote:
>>> [...]
>>> And while at it, I believe for this use, terminate_all is too strong an
>>> API to be used, perhaps we should introduce a STOP call, which just
>>> aborts the current descriptor but doesn't free it, or possibly move to
>>> submitted state/queue. And yes terminate_all should used in scenarios
>>> like free callback.
>>> That way it should map properly to ALSA PCM operations.
>> Yes, a call that would allow us to reset/restart a transfer would be nice.
>> While we are at it: Another nice addition, which would be good for sound
>> drivers is a callback, which reports the transfer's current position in the
>> datastream. This allows us to implement a pointer callback with sub-period
>> granularity and also allow us to implement the 'no period wakeup' feature. A
>> lot of DMA controllers support reporting this, but as far as I can see there
>> is currently no way to export this information using dmaengine.
> What makes you think it's missing :-)
> Pls see device_tx_status callback. You can return the descriptor
> position using this and enable "no wake mode"

Ah nice, I somehow missed it, thanks.

- Lars

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