# Re: \[PATCH v2 21/22\] sound/usb: Use Media Controller API to share media resources

- From: Takashi Iwai \<hidden\>
- Date: 2016-02-04 10:46:59 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2016/02/4677832
- Thread: https://ratatoskr.run/alsa-devel/2016/02/4677589/t.md

```text
On Thu, 04 Feb 2016 11:36:00 +0100,
Mauro Carvalho Chehab wrote:
> 
> > diff --git a/sound/usb/card.h b/sound/usb/card.h
> > index 71778ca..c15a03c 100644
> > --- a/sound/usb/card.h
> > +++ b/sound/usb/card.h
> > @@ -156,6 +156,7 @@ struct snd_usb_substream {
> >  	} dsd_dop;
> >  
> >  	bool trigger_tstamp_pending_update; /* trigger timestamp being updated from initial estimate */
> > +	void *media_ctl;
> >  };
> 
> This is Takashi's call, but I would prefer to avoid using a void *
> here. Fortunately, GCC is smart enough to handle struct pointers
> even if the header doesn't have a full declaration of the struct.
> 
> So, I would change the above to:
> 
> struct media_device;
> 
> struct snd_usb_substream {
> ...
> 	struct media_device *media_ctl;
> };
> 
> This way, we ensure strong typecast checks when compiling the code under
> sound/usb/media.c, while not needing to include media_device.h header here.

Agreed, this is no big merit to make it a void pointer.


Takashi
```