[alsa-devel] [RFC 4/7] ASoC: Add dmaengine PCM helper functions

Mark Brown broonie at opensource.wolfsonmicro.com
Wed Feb 22 14:39:39 CET 2012

On Wed, Feb 22, 2012 at 01:32:07PM +0000, Russell King - ARM Linux wrote:

> I think you're making the assumption that other people need cyclic
> transfers.  I've seen little evidence that anyone other than sound
> needs such things, so I don't think there's justification to push
> this code into every DMA engine driver.

The idea was to have the library code to do this in the dmaengine core
rather in drivers.  Doing it in the drivers would be silly, it should be
in library code somewhere.  If we are going to librify it then pushing
the code as far up the stack as we can seems like a smart move.

> Remember, there's no common code to a DMA engine driver at all,
> everyone implements their own way with their own bugs.  I would agree
> with you if there was some decent DMA engine infrastructure to abstract
> out such things, but there isn't.

> So what you're asking is for N different ways of doing this, instead of
> having one centralized way.

Well, Vinod seemed to also think that dmaengine ought to be able to cope
with emulating this and I really don't see why it shouldn't be.  It does
know the capabilities of the underlying driver and it gets to look at
all the calls going into the driver before the driver does.  If ASoC can
interpose itself I don't see why dmaengine can't.
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