Re: [PATCH] uapi: fix linux/usb/audio.h userspace compilation error

[Takashi Iwai <tiwai@suse.de>]

On Mon, 13 Aug 2018 18:01:06 +0200,
Dmitry V. Levin wrote:
> 
> On Mon, Aug 13, 2018 at 05:55:25PM +0200, Takashi Iwai wrote:
> > On Mon, 13 Aug 2018 17:46:51 +0200, Dmitry V. Levin wrote:
> > > 
> > > Replace NULL with 0 in uac_mixer_unit_bmControls() to fix the following
> > > linux/usb/audio.h userspace compilation error:
> > > 
> > > /usr/include/linux/usb/audio.h: In function 'uac_mixer_unit_bmControls':
> > > /usr/include/linux/usb/audio.h:304:10: error: 'NULL' undeclared (first use in this function)
> > >    return NULL;
> > > 
> > > Fixes: 6cfd839ae78e ("ALSA: usb-audio: UAC3. Add support for mixer unit.")
> > > Cc: <stable@vger.kernel.org> # v4.18
> > > Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
> > 
> > Hrm, can we include the standard header for definition of NULL
> > instead?  It's way too ugly to use 0 just for that.
> 
> It's fine to return 0 as a null pointer.

Fine from syntax POV, but not from semantic.

> If you prefer NULL,
> please include a header that won't break userspace,
> or just move the function out of UAPI.

Maybe better to remove the function from uapi, then.


Takashi