How to get ac97_t pointer from snd_pcm_substream_t?

How to get ac97_t pointer from snd_pcm_substream_t?

[Bill Gatliff]

Guys:

I want to call snd_ac97_set_rate() from my PCM prepare() handler.

I can't seem to figure out how to get the codec pointer (ac97 in my 
case) from a snd_pcm_substream_t.  Is it possible?

Thanks!


b.g.

-- 
Bill Gatliff
bgat@billgatliff.com



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Re: How to get ac97_t pointer from snd_pcm_substream_t?

[Takashi Iwai]

At Mon, 10 Oct 2005 12:31:22 -0500,
Bill Gatliff wrote:
> 
> Guys:
> 
> I want to call snd_ac97_set_rate() from my PCM prepare() handler.
> 
> I can't seem to figure out how to get the codec pointer (ac97 in my 
> case) from a snd_pcm_substream_t.  Is it possible?

There are several ways.

In most cases, retrieve the chip instance via snd_pcm_substream_chip()
(assuming that pcm->private_data = chip), and get ac97 instance from
it.

You can assign substream->runtime->private_data for your own purpose,
too.  It's independent from pcm or substream->private_data.

pcm->private_data and substream->private_data are usually identical.
substream->private_data is copied from pcm->private_data at open
time.  But you can override this value if you want.
For example, isa/cmipci.c uses this trick to support different
codecs.


Takashi


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