Re: Mixer improvements

[James Courtier-Dutton <James@superbug.co.uk>]

Jaroslav Kysela wrote:
> On Mon, 12 Sep 2005, Takashi Iwai wrote:
> 
> 
>>>1) Unsigned integer index to percent <-> dB function.
>>>2) Integer for Analog or Digital path. This will indicate which side of 
>>>3) Link information.
>>>4) Alternatively, we could implement this in alsa-lib, and just add 
> 
> 
> I agree that 1 is the main required extension. 2 and 3 are optional in my 
> eyes.

Agreed.

> 
> 
>>Moreover, we should be careful to handle the value <-> dB conversion.
>>The dB isn't integer in general, and defining the fixed resolution is
>>no generic solution.
> 
> 
> It's signed integer - fixed float resolution (* 100) in my implementation. 
> I think that it's enough for our purpose.

I have already checked into the alsa-utils cvs support for this API in 
alsamixer. We just need to add the features to alsa-lib and alsa-driver.

> 
> 
>>Adding a dB info into the driver would be required for the USB and HDA 
>>stuff, at least, since they can (or need) retrieve such information from 
>>the hardware directly. Meanwhile, others are basically given statically 
>>- e.g. a simple table look-up for each ac97 codec.  This isn't 
>>necessarily in the kernel code at all.

> 
> 
> I agree, the alsa-lib should have a database containing this static 
> information. Also, I think that this information does not belong to the 
> universal control API at all. We need to decide, if we need another 
> midlevel module providing this information, or in my eyes, better way 
> might be to use the hwdep device and pass this information to the user 
> space. The alsa-lib modules driving the specific hardware will parse this 
> information and do own things with it. Perhaps, we can pass simple text 
> from the driver to user space. In this way, the procfs or devfs might be 
> used.
> 
> 						Jaroslav
> 

I will take a first bash at it, provide some patch code that we can then 
discuss.

James


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