Re: Re: Re: How to access vendor specific AC97 codecregister?

[Liam Girdwood <liam.girdwood@wolfsonmicro.com>]

On Thu, 2006-04-20 at 12:37 -0400, alasinski wrote:
> Thx Liam,
> 
> > You will only be able to access these functions from an ad-hoc AC97
> > driver. Please see the UCB14xx touch driver for implementation details.
> - where I can find it ?

Please use Google.

> 
> > Alternatively, you could always export the vendor specific registers
> > using sysfs. That way your user space program could read and write to
> > the codec registers exported. I've done this with the codec GPIO status
> > register (0x54) for the WM97xx touch drivers.

As Takashi said this is really not a standard way to do this. Your
probably better of writing your own driver to handle your codec GPIO
needs.

> How to go about using sysfs() to access to registers ? It provides info on 
> file system equivalent to /proc/filesystems content I'm told. I know of one 
> way to do it: I can map registers into user space with open("/dev/mem",...) 
> followed by mmap (...). Then I'm a king and can read/write to any of them. 

This wont work for AC97 codec registers as they are not part of the host
memory map and are accessed via the hosts AC97 controller.

> > I've done this with the codec GPIO status register (0x54) for the WM97xx 
> > touch drivers.
> Did you handled AC97 initialization yourself, or you relied on other driver 
> (exp: ALSA) ?
> 

I used the standard Alsa AC97 codec driver and every thing works fine
for me.

Liam



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