[alsa-devel] [PATCH 3/3] ALSA: core: set kcontrol's count field correctly

Lu Guanqun guanqun.lu at intel.com
Wed Aug 24 14:46:38 CEST 2011

On Wed, Aug 24, 2011 at 08:05:56PM +0800, Takashi Iwai wrote:
> > Hi Takashi,
> > 
> > I don't how this approach can solve this problem.
> There is no problem.  You can't copy the data from ELEM_INFO for
> ELEM_ADD/REPLACE.  It was a wrong assumption to reuse the data.
> Instead, you had to set up the struct field manually.
> That is, the test procedure was simply wrong.
> > There's still an
> > implicit assumption here that user space application will clear
> > info->elem_count to zero before it issues the REPLACE ioctl, right?
> Yes, the point is that it's no longer same structure.  So, you can't
> copy from the result from ELEM_INFO ioctl any more.  Instead, you need
> to set up the struct field manually.

Thanks Takashi, that's the info I'm looking for. We need to state this
requirements explicitly, it seems we lack these kind of documentation and
thus it results in poorly written test cases in user space.

Is there any man pages or documentation we can state this clearly? I can
help to contribute some documentation or even add some sample programs


More information about the Alsa-devel mailing list