[alsa-devel] [PATCH] AOA: Convert onyx and tas codecs to new-style i2c drivers

Johannes Berg johannes at sipsolutions.net
Wed Apr 15 15:18:10 CEST 2009

On Wed, 2009-04-15 at 15:06 +0200, Jean Delvare wrote:

> > That would be weird -- the error path _has_ to be taken always in onyx.
> > Unless you're talking about something in the i2c core or whatever?
> Yes, i2c core or even driver core. I'll see if I can reproduce it.


> > > (...)
> > > Well, there is a dirty workaround, which I will apply for now, but...
> > > ideally the layout factory should be revisited so that the codec check
> > > happens earlier. Is this something you could help with?
> > 
> > That's not really possible unless the factory post-processes the entire
> > device-tree -- very ugly.
> What I had in mind was not so complex. Simply, we could move the
> i2c_new_device() calls into layout_found_codec(). That way we can
> decide to instantiate the I2C device if and only if check_codec() is
> successful. This is more efficient that creating the device, letting
> the driver attach to it, with probing eventually failing, and then
> removing the device if it wasn't the right one.
> That is, the i2c client would be a mere helper on top of struct
> aoa_codec, rather than the other way around.

Ah. That would probably work, but right now I have little motivation to
work on it -- I hardly use the G5 desktop machine any more.

> > > That's something which isn't too clear to me: is there a physical
> > > device at 2-0046 and 3-0046? The onyx codec is accepted for the latter,
> > > however it seems that the test of a device presence at 2-0046 succeeds
> > > as well...
> > 
> > It's the _same_ physical device.
> Wow. One I2C device which can be reached through 2 different I2C buses?
> First time I hear about something like this. Very odd. I can't see the
> point of doing this.

Hmm. How do you know it's on different buses? I don't really know
anything -- all I know is that the DT is buggered and lists the codec
twice. Since we can talk to both, then I'm sure it's just one chip, they
wouldn't put the chip in twice when you can use only one of them :)

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