[Buildroot] [RFC v1] libv4l: build utils only on MMU (with fork support) platforms
Peter Seiderer
ps.report at gmx.net
Mon Jul 24 17:38:22 UTC 2017
Hello Hugues,
On Mon, 24 Jul 2017 08:08:45 +0000, Hugues FRUCHET <hugues.fruchet at st.com> wrote:
> Hi Peter,
>
> Sorry, typo in patch, this one should work as expected.
>
> Best regards,
> Hugues.
>
Yes, the new version of the patch works:
$ make libv4l
[...]
Applying 0010-configure.ac-disable-libv4l-if-no-fork.patch using patch:
[...]
compile time options summary
============================
Host OS : linux-uclibc
X11 : no
GL : no
glu : no
libjpeg :
libudev : no
pthread : yes
fork : no
QT version : none
ALSA support : no
build dynamic libs : yes
build static libs : no
gconv : no
libv4l : no
dynamic libv4l : yes
v4l_plugins : yes
v4l_wrappers : yes
libdvbv5 : no
dvbv5-daemon : no
v4lutils : yes
qv4l2 : no
v4l2-ctl uses libv4l : yes
v4l2-compliance uses libv4l: yes
[...]
$ ls -ltr target/usr/bin/
[...]
-rwxr-xr-x 1 seiderer users 259172 Jul 24 19:29 decode_tm6000
-rwxr-xr-x 1 seiderer users 13988 Jul 24 19:29 ivtv-ctl
-rwxr-xr-x 1 seiderer users 198868 Jul 24 19:29 ir-ctl
-rwxr-xr-x 1 seiderer users 12240 Jul 24 19:29 cx18-ctl
-rwxr-xr-x 1 seiderer users 215068 Jul 24 19:29 ir-keytable
-rwxr-xr-x 1 seiderer users 53452 Jul 24 19:29 media-ctl
-rwxr-xr-x 1 seiderer users 206532 Jul 24 19:29 v4l2-compliance
-rwxr-xr-x 1 seiderer users 265676 Jul 24 19:29 v4l2-ctl
-rwxr-xr-x 1 seiderer users 188496 Jul 24 19:29 v4l2-sysfs-path
-rwxr-xr-x 1 seiderer users 154228 Jul 24 19:29 cec-ctl
-rwxr-xr-x 1 seiderer users 122344 Jul 24 19:29 cec-compliance
-rwxr-xr-x 1 seiderer users 69860 Jul 24 19:29 cec-follower
$ ls -ltr target/usr/lib
drwxr-xr-x 3 seiderer users 4096 Jul 11 19:06 libv4l
-rwxr-xr-x 1 seiderer users 39408 Jul 11 19:06 libv4l2.so.0.0.0
-rwxr-xr-x 1 seiderer users 17032 Jul 11 19:06 libv4l1.so.0.0.0
-rwxr-xr-x 1 seiderer users 105432 Jul 11 19:06 libv4lconvert.so.0.0.0
-rwxr-xr-x 1 seiderer users 18384 Jul 11 19:06 libv4l2rds.so.0.0.0
Thanks for your efforts...
Regards,
Peter
> On 07/22/2017 11:36 PM, Peter Seiderer wrote:
> > Hello Hugues,
> >
> > On Tue, 18 Jul 2017 09:08:18 +0000, Hugues FRUCHET <hugues.fruchet at st.com> wrote:
> >
> >> Hi Peter,
> >>
> >> On 07/17/2017 08:09 PM, Peter Seiderer wrote:
> >>> Hello Hugues,
> >>>
> >>> On Mon, 17 Jul 2017 10:07:07 +0000, Hugues FRUCHET <hugues.fruchet at st.com> wrote:
> >>>
> >>>> Hi Peter,
> >>>>
> >>>> I have tested on STM32 platform running Cortex F family having no MMU,
> >>>> shared libraries are disabled (no dlopen) and no fork supported on our
> >>>> setup.
> >>>>
> >>>> libv4lconvert should not have been built at all, because entire lib/
> >>>> folder build is conditional to shared library support:
> >>>> * configure.ac
> >>>> AM_CONDITIONAL([WITH_LIBV4L], [test x$enable_libv4l != xno -a
> >>>> x$enable_shared != xno])
> >>>> * Makefile.am
> >>>> [...]
> >>>> +if WITH_LIBV4L
> >>>> +SUBDIRS += lib
> >>>> +endif
> >>>
> >>> A little bit confused, one of the patches you introduced changed it to:
> >>>
> >>> - without WITH_LIBV4L: no libv4l libraries at all
> >>> - without WITH_DYN_LIBV4L: only static libraries, no dynamic libraries
> >>>
> >>> And from configure --help:
> >>>
> >>> --disable-libv4l disable libv4l compilation
> >>> --disable-dyn-libv4l disable dynamic libv4l support
> >>
> >> This package is named "libv4l" in buildroot but repo name is "v4l-utils"
> >> which contains:
> >> 1) some library plugins on top of V4L kernel interface in order to
> >> intercept user calls and hook/convert to the appropriate kernel call.
> >> => so called "libv4l" and located in "lib/" folder
> >> 2) some utilities located in "utils/" folder, such as the V4L compliancy
> >> tool "v4l2-compliance" or the CEC compliancy tool "cec-compliance" which
> >> are calling either the libv4l interface (default), the libv4l interface
> >> but statically linked inside utilities (--disable-dyn-libv4l) or the V4L
> >> kernel interface directly (--disable-libv4l).
> >> Hope that helps to better understand the options.
> >>
> >>>
> >>>>
> >>>> But checking your log I see that --enable-shared is set, so it seems
> >>>> that you are supporting shared libraries on no-MMU platform but without
> >>>> fork() support, is my understanding correct ?
> >>>>
> >>>
> >>> Yes...
> >>>
> >>>> What you can do to fix build is to force disabling of libs inside libv4l
> >>>> package:
> >>>>
> >>>> package/libv4l/libv4l.mk
> >>>> +ifeq ($(BR2_USE_MMU),)
> >>>> +LIBV4L_CONF_OPTS += --disable-libv4l
> >>>> +endif
> >>>
> >>> Works, but feels wrong: A package named libv4l enabled and building/installing
> >>> nothing (except when LIBV4L_UTILS is enabled)...
> >>
> >> Right.
> >> The aim of the no-MMU dependency removal patchset was to enable build of
> >> "utils" even on no-MMU platform. This is required to build at least the
> >> 2 mandatory compliancy tools:
> >> - v4l-compliance: its test report is required by V4L maintainers and is
> >> to be attached to the cover letter of any V4L driver pushed upstream.
> >> - cec-compliance: the same for CEC drivers.
> >>
> >>
> >> Please note that you cannot use the libv4l plugins mechanism without
> >> having fork() support, see libv4lconvert/helper.c,
> >> v4lconvert_helper_start().
> >
> > Yes, but only libv4lconvert needs fork, all other libraries not...,
> > without fork support only libv4lconvert (and all dependent utils)
> > should not be built...
> >
> >> Means that only V4L utilities can be currently supported on no-MMU
> >> platforms.
> >>
> >> Back to your exact build issue, the best fix on my opinion is to add a
> >> dependency on fork() symbol in configure.ac instead of the one proposed
> >> in libv4l.mk, find attached a patch proposal.
> >
> > Patch did not work:
> >
> > $ make libv4l
> > [...]
> > compile time options summary
> > ============================
> >
> > Host OS : linux-uclibc
> > X11 : no
> > GL : no
> > glu : no
> > libjpeg :
> > libudev : no
> > pthread : yes
> > fork : no
> > QT version : none
> > ALSA support : no
> >
> > build dynamic libs : yes
> > build static libs : no
> >
> > gconv : no
> >
> > libv4l : yes
> > dynamic libv4l : yes
> > v4l_plugins : yes
> > v4l_wrappers : yes
> > libdvbv5 : no
> > dvbv5-daemon : no
> > v4lutils : yes
> > qv4l2 : no
> > v4l2-ctl uses libv4l : yes
> > v4l2-compliance uses libv4l: yes
> > [...]
> > helper.c: In function ‘v4lconvert_helper_start’:
> > helper.c:64:25: warning: implicit declaration of function ‘fork’ [-Wimplicit-function-declaration]
> > data->decompress_pid = fork();
> > ^~~~
> > [...]
> > CXXLD v4l2-compliance
> > .../build_bfin_libv4l_fix_fork_001/build/libv4l-1.12.5/lib/libv4lconvert/.libs/libv4lconvert.so: undefined reference to `fork'
> > collect2: error: ld returned 1 exit status
> >
> > Regards,
> > Peter
> >
> >
> >>
> >>
> >> Regards,
> >> Hugues.
> >>>
> >>> Regards,
> >>> Peter
> >>>
> >>>>
> >>>> Hoping that helps.
> >>>>
> >>>> Best regards,
> >>>> Hugues.
> >>>>
> >>>> On 07/11/2017 07:26 PM, Peter Seiderer wrote:
> >>>>> Fixes [1]:
> >>>>>
> >>>>> CXXLD v4l2-compliance
> >>>>> .../output/build/libv4l-1.12.5/lib/libv4lconvert/.libs/libv4lconvert.so: undefined reference to `fork'
> >>>>> collect2: error: ld returned 1 exit status
> >>>>>
> >>>>> [1] http://autobuild.buildroot.net/results/7e8/7e8fbd99a8c091d7bbeedd16066297682bbe29fe
> >>>>>
> >>>>> Signed-off-by: Peter Seiderer <ps.report at gmx.net>
> >>>>> ---
> >>>>> The libv4l build for noMMU platforms was enabled with commit 'package/libv4l:
> >>>>> allow build of v4l2 utilities on noMMU platforms' (see [2]). But libv4lconvert uses
> >>>>> fork internally, so all utils linking against fail to build. Fix this by disabling
> >>>>> the utils on noMMU platforms (so keep building all libraries).
> >>>>>
> >>>>> Alternatives would be:
> >>>>>
> >>>>> - disable libv4l on all noMMU platforms (not only the utils), revert a part
> >>>>> of commit [2]
> >>>>>
> >>>>> - create a patch to disable only libv4lconvert (and all dependend utils)
> >>>>> on noMMU platforms
> >>>>>
> >>>>> [2] https://git.buildroot.net/buildroot/commit/?id=f837251785e9389f53d695ddb8a094707865171b
> >>>>> ---
> >>>>> package/libv4l/Config.in | 1 +
> >>>>> 1 file changed, 1 insertion(+)
> >>>>>
> >>>>> diff --git a/package/libv4l/Config.in b/package/libv4l/Config.in
> >>>>> index e7f78dc70f..61c290f251 100644
> >>>>> --- a/package/libv4l/Config.in
> >>>>> +++ b/package/libv4l/Config.in
> >>>>> @@ -19,6 +19,7 @@ comment "libv4l JPEG support not enabled"
> >>>>>
> >>>>> config BR2_PACKAGE_LIBV4L_UTILS
> >>>>> bool "v4l-utils tools"
> >>>>> + depends on BR2_USE_MMU # fork(), used in libv4lconvert linked by various utils eg. v4l2-compliance
> >>>>> help
> >>>>> v4l-utils is a collection of various video4linux and DVB utilities.
> >>>>> Enable this if you want to build the following tools:
> >>>>>
> >>>> _______________________________________________
> >>>> buildroot mailing list
> >>>> buildroot at busybox.net
> >>>> http://lists.busybox.net/mailman/listinfo/buildroot
> >>>
> >
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