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

["alasinski" <alasinski@rogers.com>]

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 ?

> 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.
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 is actually my fallback plan if ALSA proves to be to difficult (which 
start looking right now). Interacting with registers directly from a user 
program is not a recommended way: first timing become an issue, secondly I'm 
afraid of  unexpected interaction with a driver that is already loaded, 
thirdly there is an initialization stuff that needs to be done on UCB1400 as 
part of generic AC97 "bring to life" that I would rather delegate to ALSA 
driver rather then go over it all myself.

> 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) ?


cheers
-al

"Liam Girdwood" <liam.girdwood@wolfsonmicro.com> wrote in message 
news:1145549628.25762.4.camel@localhost.localdomain...
> On Thu, 2006-04-20 at 11:48 -0400, alasinski wrote:
>> Thx Lee,
>>
>> I have looked at pxa2xx-ac97.c driver. It provides generic functions to
>> read/write any ac97 register: pxa2xx_ac97_read/write that are made 
>> available
>> to generic ac97_codec with snd_ac97_bus() call. My problem is I don't 
>> know
>> how to invoke those functions with proper arguments from application 
>> level.
>
> You will only be able to access these functions from an ad-hoc AC97
> driver. Please see the UCB14xx touch driver for implementation details.
>
> 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.
>
> HTH
>
> Liam
>
>
>
>
>
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-------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642