[alsa-devel] Why is substream->pcm->dev == NULL?

[Takashi Iwai]

At Thu, 07 Aug 2008 13:51:55 -0500,
Timur Tabi wrote:
> 
> In my _pointer callback function, I have this:
> 
> printk(KERN_INFO "%s:%u substream->pcm->dev=%p, substream->pcm->card->dev=%p\n",
> __func__, __LINE__, substream->pcm->dev, substream->pcm->card->dev);
> 
> During playback, it displays this:
> 
> fsl_dma_pointer:698 substream->pcm->dev=00000000, substream->pcm->card->dev=dfa50a08
> 
> Why is substream->pcm->dev == NULL?  What's the point of having this field if
> you're not going to use it?

It's provided to use a different device for PCM than card->dev.
An example is found in AOA drivers.


Takashi