Re: Driver Programming

[K.Fetscher@t-online.de (Klaus Fetscher)]

Thanks Clemens and Giuliano for the answers !

>>I want to programm an driver for the Cirrus CS42516. This Codec
>>communicates with an ARM9 CPU over 3 I2S channels. I want to use 3
>>stereo channels for playing and two stereo channels for receiving the
>>data. All three channels are working with the same clock-rate.
>>
>>I have read the documentation "Writing an Alsa Driver" but I am confused
>>about the meaning of PCM Streams and Substreams. What must I declare,
>>one PCM Stream with three Substreams or 3 PCM Streams ?
>>    
>>
>How does your chip work ?  If I inderstood you correcty, it has three
>independent stereo outputs and two inputs.
>
>  
>
Yes, but all stereo channels must work with the same sampling rate.

>snd_pcm_new(chip->card, "name", DEV_0, THREE_OUT, TWO_IN, &pcm);
>
>If each substream can be either mono or stereo, in the
>.open() callback you'll set
>
>runtime->hw->channels_min = 1;
>runtime->hw->channels_max = 2;
>
>  
>
Okay, I am using these parameters for the function snd_pcm_new(  ).

Is it possible to detect (in the functions xxx_playback_prepare, 
xxx_capture_prepare ...), which substream will be used.
I need to know the number of the substream, because I have three FIFO's 
for transmitting and two FIFO's for receiving and I want to program a 
dedicated DMA-Controllers for every substream.

Is it possible, to select a substream with aplay ?


Thanks

Klaus



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