Re: How to access vendor specific AC97 codec register ?

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

Thx Takashi,

since I'm not being well frased in ALSA terminology I need some guidance:
- what "accessor" is ?
- Is it part of the driver or asoundlib ?
- what ALSA files, calls are involved ?
- where can I find some explanation on it ?
- do you have a sample that implements other (similar ?) accessor ?

cheers
-al

"Takashi Iwai" <tiwai@suse.de> wrote in message 
news:s5hbquwb7f0.wl%tiwai@suse.de...
> At Thu, 20 Apr 2006 11:05:38 -0400,
> alasinski wrote:
>>
>> Hi,
>>
>> I need to do IO specific operation from UCB1400 on Snapper Arm board. 
>> This
>> has to be done from C code as it is part of a larger project. All what I
>> need is to be able to read and write content of the few vendor specific 
>> AC97
>> codec registers: 0x5A,0x5C. I'm not interested with any other ALSA
>> functionality.
>>
>> I have ALSA installed and running with simple programs that can 
>> successfully
>> open controller with snd_ctl_open () and list available control elements.
>> This is basically J.C.Georgas sample I found. I can read content of all 
>> AC97
>> registers by cat /proc/asound/card0/codec97#/ac97#0-0+regs. That assures 
>> me
>> that all driver and lib parts are working. All what I need is to write a
>> simple piece of code ....
>>
>> However, I spent 2 days reading through ALSA back and forth and I find 
>> this
>> task very daunting to say at least. For one things I was not able to find 
>> an
>> architecture document explaining how parts of ALSA work, to be able to 
>> find
>> some sort of direction. There are samples dedicated to solving some of a
>> problems, unfortunately not my problem. Man pages and reference are only
>> little more then code browsing. Tutorials explain in brief what I don't 
>> need
>> to know. In summary: typical situation when you are tasked with something
>> that is off main stream.
>>
>> I have an inkling that I should prepare UCB1400.conf file to define 
>> control
>> elements that map to the registers (how ?). Then I should be able to
>> snd_ctl_elem_read() or .._write() to them. Perhaps there is other way
>> around: something like making ioctl() call on a driver directly w/o
>> libasound. I'm in lost.
>
> You have to implement an accessor (e.g. via ALSA control API) to the
> certain ac97 registers in the driver.  There is no generic interface
> allowing you to access the all ac97 registers.
> (The proc file is an exception.  It's provided only for debugging
> purpose.)
>
>
> Takashi
>
>
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