[alsa-devel] [PATCH v2] ALSA: usb-audio: Recurse before saving terminal properties

[Takashi Iwai]

On Wed, 19 Aug 2015 17:17:19 +0200,
Daniel Mack wrote:
> 
> On 08/19/2015 09:28 AM, Julian Scheel wrote:
> > The input terminal parser recurses into the referenced clock entity to verify
> > it is existant and thus the terminal descriptor is valid. The actual property
> > values of the term instance which is initially parsed must not be overriden by
> > the recursion. For this to work the term properties have to be assigned after
> > recursing into the referenced clock entity descriptors.
> > 
> > Signed-off-by: Julian Scheel <julian at jusst.de>
> 
> Given your explanations, I believe this is the right thing to do.
> 
> Acked-by: Daniel Mack <daniel at zonque.org>

Thanks.  It's no urgent fix, I'm going to queue it to for-next
branch.


Takashi

> 
> 
> Thanks!
> 
> 
> > ---
> > Changes in v2:
> > - Store term->id after recursion as well, as it gets overriden in the
> >   recursion
> > - Add comments explaining that the recursion is only for validation of the
> >   descriptor validity
> > ---
> >  sound/usb/mixer.c | 16 +++++++++++-----
> >  1 file changed, 11 insertions(+), 5 deletions(-)
> > 
> > diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> > index 81055d3..c50790c 100644
> > --- a/sound/usb/mixer.c
> > +++ b/sound/usb/mixer.c
> > @@ -731,15 +731,21 @@ static int check_input_term(struct mixer_build *state, int id,
> >  				term->name = d->iTerminal;
> >  			} else { /* UAC_VERSION_2 */
> >  				struct uac2_input_terminal_descriptor *d = p1;
> > -				term->type = le16_to_cpu(d->wTerminalType);
> > -				term->channels = d->bNrChannels;
> > -				term->chconfig = le32_to_cpu(d->bmChannelConfig);
> > -				term->name = d->iTerminal;
> >  
> > -				/* call recursively to get the clock selectors */
> > +				/* call recursively to verify that the
> > +				 * referenced clock entity is valid */
> >  				err = check_input_term(state, d->bCSourceID, term);
> >  				if (err < 0)
> >  					return err;
> > +
> > +				/* save input term properties after recursion,
> > +				 * to ensure they are not overriden by the
> > +				 * recursion calls */
> > +				term->id = id;
> > +				term->type = le16_to_cpu(d->wTerminalType);
> > +				term->channels = d->bNrChannels;
> > +				term->chconfig = le32_to_cpu(d->bmChannelConfig);
> > +				term->name = d->iTerminal;
> >  			}
> >  			return 0;
> >  		case UAC_FEATURE_UNIT: {
> > 
>