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SubjectRe: Confusion in usr/include/linux/videodev.h
On Wed, 21 Jan 2009, Arnd Bergmann wrote:
> On Wednesday 21 January 2009, Jaswinder Singh Rajput wrote:
> > > diff -r 29c5787efcda linux/include/linux/videodev.h
> > > --- a/linux/include/linux/videodev.h Thu Jan 15 09:07:03 2009 -0800
> > > +++ b/linux/include/linux/videodev.h Wed Jan 21 00:51:45 2009 -0800
> > > @@ -15,7 +15,8 @@
> > > #include <linux/ioctl.h>
> > > #include <linux/videodev2.h>
> > >
> > > -#if defined(CONFIG_VIDEO_V4L1_COMPAT) || !defined (__KERNEL__)
> > > +#if (defined(__KERNEL__) && defined(CONFIG_VIDEO_V4L1_COMPAT)) \
> > > + || !defined (__KERNEL__)
> > >
> > > #define VID_TYPE_CAPTURE 1 /* Can capture */
> > > #define VID_TYPE_TUNER 2 /* Can tune */
> > >
> > > Now CONFIG_VIDEO_V4L1_COMPAT will only be used in the kernel.
> > >
> >
> > No, this will still give warnings.
>
> You could #define another conditional, like this:
>
> #ifndef __KERNEL__
> # define __V4L1_COMPAT_API /* Always provide definitions to user space */
> #else /* __KERNEL__ */
> # ifdef CONFIG_VIDEO_V4L1_COMPAT
> # define __V4L1_COMPAT_API
> # endif /* CONFIG_VIDEO_V4L1_COMPAT /*
> #endif /* __KERNEL__ */

I see what the real problem is now, the unifdef program isn't smart enough
to realize that it knows the result of !defined(__KERNEL__) || defined(FOO)
and so it keeps those ifdefs in when it should be able to remove them.
This works too:

#ifndef __KERNEL__
# define __V4L1_COMPAT_API /* Always provide definitions to user space */
#elif defined(CONFIG_VIDEO_V4L1_COMPAT) /* __KERNEL__ */
# define __V4L1_COMPAT_API
#endif /* CONFIG_VIDEO_V4L1_COMPAT */

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