Re: Linux driver for cs4281 with TWO cs4299 codecs?

[Takashi Iwai <tiwai@suse.de>]

At Mon, 27 May 2002 18:37:09 +0200 (CEST),
tomasz motylewski wrote:
> 
> Now I have got all alsa9 utilites on the system and the driver does something.
> 
> I can see for example PCM (2 channels) and PCM 1 (2 channels) in alsamixer.
> 
> I can also record like: arecord -c 4 -t raw -f S16_LE aaa.raw
> and I get:
> od -i aaa.raw | more
> 0000000    -10     -6      0      0      1      3      0      0
> 0000020     -8     -8      0      0     -7     -7      0      0
> 0000040     -7     -6      0      0     -6     -2      0      0
> 0000060    -10     -9      0      0     -9     -8      0      0
> 
> But here is a problem - I would expect to see some noise in both codecs - I
> have configured and unmuted them BOTH to max volume.
> 
> In fact I have tried also -c 3 and -c 5  and always only the first 2 channels
> are non-zero.
> 
> arecord -l    
> card 0: card0 [Cirrus Logic CS4281], device 0: CS4281 [CS4281]
>   Subdevices: 1/1
>   Subdevice #0: subdevice #0
> 
> How can I record data from the secondary codec?
 
the patch i made was only for enabling the 2nd codec.
it does nothing actually about playback/capture using the 2nd codec
yet, so it's normal that you receive the result above.
the multi-channel was _emulated_ in alsa-lib.

i've not read the spec of cs4281 precisely, but there must be setting
to specify which codec is used for playback/capture.
sorry, i have no time atm for digging more about this.
do you have clue about this?

anyway, what we need to do on the driver are:

- increase the number of channels for pcm playback/capture, or create
  the second pcm stream for 2nd codec.
- set up the codec in prepare(), hw_params() or open() callback.
  disable in close() if necessary.

please check other hardwares with double codecs.


> 
> BTW. I have done:
...
> 
> I believe this is a nice way to give the actual codec ID (0 is always the
> primary codec).

yes.  but the exactly same hack was already on cvs at last week ;)


Takashi

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