[libcamera-devel] [PATCH v2] v4l2: Provide libcamerify wrapper script
Kieran Bingham
kieran.bingham at ideasonboard.com
Tue Feb 1 11:26:06 CET 2022
Quoting Laurent Pinchart (2022-02-01 07:20:52)
> Hi Kieran,
>
> Thank you for the patch.
>
> On Mon, Jan 31, 2022 at 09:07:57PM +0000, Kieran Bingham wrote:
> > Support easier usage of the v4l2 compatibility layer with a script that
>
> s/v4l2/V4L2/
>
> > handles the LD_PRELOAD for applications.
> >
> > The wrapper can be prefixed to launch any application with the preload
> > set:
> >
> > $ libcamerify v4l2-ctl --list-devices
> > \_SB_.PCI0.GP13.XHC0.RHUB.PRT4- (libcamera:0):
> > /dev/video0
> >
> > platform/vimc.0 Sensor B (libcamera:1):
> > /dev/video2
> > /dev/video3
> > /dev/video4
> >
> > Specifying '-d' once before the command to run will enable V4L2Compat
> > layer debug output from libcamera.
> >
> > Specifying '-d' twice will enable all debug levels from all libcamera
> > components and provide a very detailed log for analysis.
> >
> > Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> > ---
> > v2:
> > - rename to libcamerify (from libcamera-v4l2)
> > - add extending support for setting debug log levels.
> >
> >
> > src/v4l2/libcamerify.in | 34 ++++++++++++++++++++++++++++++++++
> > src/v4l2/meson.build | 14 ++++++++++++++
> > 2 files changed, 48 insertions(+)
> > create mode 100755 src/v4l2/libcamerify.in
> >
> > diff --git a/src/v4l2/libcamerify.in b/src/v4l2/libcamerify.in
> > new file mode 100755
> > index 000000000000..161f5e49190e
> > --- /dev/null
> > +++ b/src/v4l2/libcamerify.in
> > @@ -0,0 +1,34 @@
> > +#!/bin/sh
>
> License ?
>
> > +
> > +if [ "$LD_PRELOAD" = "" ] ; then
> > + LD_PRELOAD='@LIBCAMERA_V4L2_SO@'
> > +else
> > + LD_PRELOAD="$LD_PRELOAD "'@LIBCAMERA_V4L2_SO@'
> > +fi
> > +
> > +export LD_PRELOAD
>
> Can you move this just before the exec call, to avoid LD_PRELOADing the
> library in other commands executed by thie script ?
Eeep yes. How did I miss that.
>
> > +
> > +help() {
> > + echo "$0: Load an application with libcamera V4L2 compatibility layer preload"
> > + echo " $0 [OPTIONS...] executable [args]"
> > + echo " -d, --debug Increase log level"
> > + exit 1;
> > +}
> > +
> > +debug=0
> > +while [ $# -gt 0 ]; do
> > + case $1 in
> > + -d|--debug) debug=$((debug+1));;
> > + -h) help; break;;
>
> "break" should be "exit 0".
help() was already calling exit 1;, but yes, I can move that in here.
>
> > + --) shift; break;;
> > + -*) echo "Unrecognised option: $1"; help; break;;
>
> Same here.
>
> > + *) break;;
>
> I'd find this more readable:
>
> -d|--debug)
> debug=$((debug+1))
> ;;
> -h)
> help
> break
> ;;
> --)
> shift
> break
> ;;
> -*)
> echo "Unrecognised option: $1"
> help
> break
> ;;
> *)
> break
> ;;
>
sure
> > + esac
> > + shift
> > +done
> > +
> > +[ $debug -gt 0 ] && loglevel=V4L2Compat:0
> > +[ $debug -gt 1 ] && loglevel=0
> > +[ "$loglevel" != "" ] && export LIBCAMERA_LOG_LEVELS=$loglevel
> > +
> > +exec "$@"
> > diff --git a/src/v4l2/meson.build b/src/v4l2/meson.build
> > index f78497b6799b..07ff9a6939d2 100644
> > --- a/src/v4l2/meson.build
> > +++ b/src/v4l2/meson.build
> > @@ -33,3 +33,17 @@ v4l2_compat = shared_library('v4l2-compat',
> > install : true,
> > dependencies : [libcamera_private, libdl],
> > cpp_args : v4l2_compat_cpp_args)
> > +
> > +# Provide a wrapper script to support easily loading applications with the V4L2
> > +# adaptation layer
> > +
> > +config_h.set('LIBCAMERA_V4L2_SO', get_option('prefix') / get_option('libdir') / 'v4l2-compat.so')
>
> I don't think this should be added to config.h. Can you create a
> separate variable ?
>
> cdata = configuration_data()
> cdata.set('LIBCAMERA_V4L2_SO', get_option('prefix') / get_option('libdir') / 'v4l2-compat.so')
>
> I also wonder if we could use v4l2_compat.name() instead of
> 'v4l2-compat.so' (but that's only available starting in meson 0.54).
I also asked in IRC #meson about this, hoping I could get a binary
target to tell me it's full installation path but alas...
>
> > +
> > +summary({
> > + 'LIBCAMERA_V4L2_SO' : config_h.get('LIBCAMERA_V4L2_SO'),
> > +}, section : 'Paths')
>
> I would have skipped this. It's a bit out of place, with all the other
> paths being directories.
But it's also a path/file that (at least without this script) people need to
know, so that tehy can do LD_PRELOAD= themselves.
I can drop it though, as I expect this script will help exactly those
users.
> > +
> > +configure_file(input : 'libcamerify.in',
> > + output : 'libcamerify',
> > + configuration : config_h,
> > + install_dir : get_option('bindir'))
>
> --
> Regards,
>
> Laurent Pinchart
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