[alsa-devel] [PATCH v6] ASoC: add RT286 CODEC driver

Mark Brown broonie at kernel.org
Wed May 7 21:49:47 CEST 2014

On Wed, May 07, 2014 at 08:21:02PM +0200, Lars-Peter Clausen wrote:
> On 05/07/2014 08:07 PM, Mark Brown wrote:

> >What you just described is what I'd consider a virtual control - I don't
> >consider the fact that the put callbacks end up writing to the hardware
> >particularly substantial, as far as the framework is concerned some
> >driver specific thing goes off and does something but it could be
> >setting a variable just as well as writing to hardware.

> Ok, but we have controls that have virtual in their name, so I think it
> should be made clear that you are not talking about those.

My first thought would be to extend those so we have callbacks when
required, to be honest I'd forgotten they weren't there already.

> I think the drivers you are thinking of are those which had physical
> register which were backed by hardware and virtual register which were
> backed by software. For the later we introduced the virtual controls, so
> that such hacks are no longer necessary in driver. But in the case of the
> RT286 all the register all still backed by hardware except that the way they
> are accessed is not very uniform (different types of registers use a
> different message format, there is a asymmetry between reading and writing

Right, to me that's not actually a register map at all since it's
missing so many of the assumptions that back up register maps.

> the same data). In a sense this is similar to devices which have registers
> with different sizes, we also support these with custom regmap callbacks.

But those are only breaking that one assumption so they fit into the
idea of a register map much more readily - it's really only the physical
I/O code that actually notices anything, all the cache and other
operations can carry on uninterrupted.
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