[alsa-devel] [PATCH][ASoC v2] Update Freescale MPC8610HPCD fabric driver to support multiple codecs
jonsmirl at gmail.com
Fri Jun 13 16:29:16 CEST 2008
On 6/13/08, Timur Tabi <timur at freescale.com> wrote:
> Jon Smirl wrote:
> > On 6/13/08, Mark Brown <broonie at opensource.wolfsonmicro.com> wrote:
> >> On Thu, Jun 12, 2008 at 10:57:39PM -0400, Jon Smirl wrote:
> >> > In my model a lot of the code in your fabric driver would be pushed
> >> > into the ssi driver. So if you used ssi and a codec in the standard
> >> > manner, the board wouldn't need a fabric driver at all. That would
> >> > probably be the case for most AC97/HDA systems.
> >> I'd certainly like to see some standard support for setting up at least
> >> AC97 DAI links automatically based on the probed codec. That bit could
> >> probably be done by the core. HDA should be amenable to this model too
> >> but I haven't looked at it in anything more than passing detail yet.
> >> That's only part of the story, though. What's much more tricky is
> >> making the decision that you've got all the components for the sound
> >> subsystem - for example, there are AC97 codecs like the WM9712 and
> >> WM9713 which also have I2S interfaces. You also get systems which need
> >> to jump through hoops to set up the clocking since they're doing
> >> non-standard things. Simple systems would probably need an explict flag
> >> to say that they could be handled as such, which isn't a million miles
> >> off having something to load a generic machine driver.
> > We can't eliminate a fabric driver is all cases, I'd just like to
> > minimize its need. This code has the card and codec creation code in
> > the fabric driver, I would push down into the ssi driver. Code in the
> > ssi would locate the codec and load it. The model needs to be able to
> > function if there is no need for a fabric driver.
> Like I said earlier, I don't like this idea. I don't want all this gunk in the
> SSI driver, and I don't see anything wrong with the fabric driver being the
> master that sets up all the inter-device connections.
That forces every board to copy/paste the fabric driver and then makes
tweaks to it even if it doesn't need board specific code.
> > That also flips things around, now the ssi driver needs to locate the
> > fabric driver, not the other way around. In this model the fabric
> > driver doesn't need to make a device, it just becomes a library of
> > code called by the ssi driver.
> The DMA driver is already a library that is called by the SSI. It registers
> itself as a regular driver, but under ASoC V2, it really acts like a library.
> > Code in the ssi driver could make a
> > list of codec parameters, pass it to the fabric driver for
> > modification, and then set it into the codec.
> That sounds too complicated.
> > We're missing a cross platform way to set parameters into a codec.
> No we're not. ASoC already provides an API for sending parameters to a codec,
> and if we need more than that, we can create platform resources and pass those
> to the codec.
> Timur Tabi
> Linux kernel developer at Freescale
jonsmirl at gmail.com
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