From mboxrd@z Thu Jan  1 00:00:00 1970
From: Lars-Peter Clausen <lars@metafoo.de>
Subject: Re: [PATCH 19/19] ASoC: fsi: Add DMAEngine support
Date: Mon, 06 Feb 2012 09:47:31 +0100
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To: Vinod Koul <vinod.koul@linux.intel.com>
Cc: Linux-ALSA <alsa-devel@alsa-project.org>, Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>, Sascha Hauer <s.hauer@pengutronix.de>, Mark Brown <broonie@opensource.wolfsonmicro.com>, Wolfram Sang <w.sang@pengutronix.de>, Ralf Baechle <ralf@linux-mips.org>, H Hartley Sweeten <hsweeten@visionengravers.com>, Kuninori Morimoto <kuninori.morimoto.gx@gmail.com>, Liam Girdwood <lrg@slimlogic.co.uk>
List-Id: alsa-devel@alsa-project.org

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.

- Lars