Confusion in usr/include/linux/videodev.h

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Date: Wed, 21 Jan 2009 00:54:07 -0800 (PST)
From: Trent Piepho <xyzzy@speakeasy.org>
To: Jaswinder Singh Rajput <jaswinderlinux@gmail.com>
cc: Mauro Carvalho Chehab <mchehab@infradead.org>,
	Jaswinder Singh Rajput <jaswinder@kernel.org>,
	linux-media@vger.kernel.org, video4linux-list@redhat.com,
	Sam Ravnborg <sam@ravnborg.org>, Ingo Molnar <mingo@elte.hu>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: Confusion in usr/include/linux/videodev.h
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Commit Message

Trent Piepho Jan. 21, 2009, 8:54 a.m. UTC

On Wed, 21 Jan 2009, Jaswinder Singh Rajput wrote:
> On Wed, Jan 21, 2009 at 7:20 AM, Mauro Carvalho Chehab
> <mchehab@infradead.org> wrote:
> > On Wed, 21 Jan 2009 07:10:38 +0530
> > Jaswinder Singh Rajput <jaswinder@kernel.org> wrote:
> >
> >> usr/include/linux/videodev.h is giving 2 warnings in 'make headers_check':
> >>  usr/include/linux/videodev.h:19: leaks CONFIG_VIDEO to userspace where it is not valid
> >>  usr/include/linux/videodev.h:314: leaks CONFIG_VIDEO to userspace where it is not valid
> >>
> >> Whole file is covered with #if defined(CONFIG_VIDEO_V4L1_COMPAT) || !defined (__KERNEL__)
> >>
> >> It means this file is only valid for kernel mode if CONFIG_VIDEO_V4L1_COMPAT is defined but in user mode it is always valid.
> >
> > V4L1 is the old deprecated userspace API for video devices. It is still
> > required by some userspace applications. So, on userspace, it should be
> > included. Also, this allows that one userspace app to be compatible with both
> > V4L2 API (the current one) and the legacy V4L1 one.
> >
> > It should be noticed that are still a few drivers using the legacy API yet to
> > be converted.
> >
>
> If you have no objections then I will make a patchset which do followings:
> 1. Remove  #if defined(CONFIG_VIDEO_V4L1_COMPAT) || !defined
> (__KERNEL__) from include/linux/videodev.h
> 2. cover all #include <linux/videodev.h> with #ifdef
> CONFIG_VIDEO_V4L1_COMPAT in kernel
>
> By this way, we can satisfy both kernel space and userspace issue and
> also get rid of above warnings.
>
> If you have better suggestion then let me know.

That sounds like it will add a mess of #if's.  How about this?


Now CONFIG_VIDEO_V4L1_COMPAT will only be used in the kernel.
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Comments

Jaswinder Singh Rajput Jan. 21, 2009, 8:59 a.m. UTC | #1

On Wed, Jan 21, 2009 at 2:24 PM, Trent Piepho <xyzzy@speakeasy.org> wrote:
> On Wed, 21 Jan 2009, Jaswinder Singh Rajput wrote:
>> On Wed, Jan 21, 2009 at 7:20 AM, Mauro Carvalho Chehab
>> <mchehab@infradead.org> wrote:
>> > On Wed, 21 Jan 2009 07:10:38 +0530
>> > Jaswinder Singh Rajput <jaswinder@kernel.org> wrote:
>> >
>> >> usr/include/linux/videodev.h is giving 2 warnings in 'make headers_check':
>> >>  usr/include/linux/videodev.h:19: leaks CONFIG_VIDEO to userspace where it is not valid
>> >>  usr/include/linux/videodev.h:314: leaks CONFIG_VIDEO to userspace where it is not valid
>> >>
>> >> Whole file is covered with #if defined(CONFIG_VIDEO_V4L1_COMPAT) || !defined (__KERNEL__)
>> >>
>> >> It means this file is only valid for kernel mode if CONFIG_VIDEO_V4L1_COMPAT is defined but in user mode it is always valid.
>> >
>> > V4L1 is the old deprecated userspace API for video devices. It is still
>> > required by some userspace applications. So, on userspace, it should be
>> > included. Also, this allows that one userspace app to be compatible with both
>> > V4L2 API (the current one) and the legacy V4L1 one.
>> >
>> > It should be noticed that are still a few drivers using the legacy API yet to
>> > be converted.
>> >
>>
>> If you have no objections then I will make a patchset which do followings:
>> 1. Remove  #if defined(CONFIG_VIDEO_V4L1_COMPAT) || !defined
>> (__KERNEL__) from include/linux/videodev.h
>> 2. cover all #include <linux/videodev.h> with #ifdef
>> CONFIG_VIDEO_V4L1_COMPAT in kernel
>>
>> By this way, we can satisfy both kernel space and userspace issue and
>> also get rid of above warnings.
>>
>> If you have better suggestion then let me know.
>
> That sounds like it will add a mess of #if's.  How about this?
>
> 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.

Please run 'make headers_check'

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JSR
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Arnd Bergmann Jan. 21, 2009, 9:09 a.m. UTC | #2

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__ */

	Arnd <><
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Trent Piepho Jan. 21, 2009, 9:51 a.m. UTC | #3

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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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 */

Confusion in usr/include/linux/videodev.h

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