[libcamera-devel] [PATCH v4] v4l2: Provide libcamerify wrapper script

[paul.elder at ideasonboard.com]

Hi Kieran,

On Tue, Feb 01, 2022 at 05:18:20PM +0000, Kieran Bingham wrote:
> Support easier usage of the v4l2 compatibility layer with a script that
> handles the LD_PRELOAD for applications.
> 
> The wrapper can be prefixed to launch any application with the preload
> set:
> 
>  $ libcamera-v4l2 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>

Reviewed-by: Paul Elder <paul.elder at ideasonboard.com>

> ---
> v4:
>  - Fix up forgotten cleanup in the meson.build and remove path summary.
> 
>  src/v4l2/libcamerify.in | 47 +++++++++++++++++++++++++++++++++++++++++
>  src/v4l2/meson.build    | 11 ++++++++++
>  2 files changed, 58 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..c4ea273fa627
> --- /dev/null
> +++ b/src/v4l2/libcamerify.in
> @@ -0,0 +1,47 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +
> +help() {
> +	echo "$0: Load an application with libcamera V4L2 compatibility layer preload"
> +	echo " $0 [OPTIONS...] executable [args]"
> +	echo " -d, --debug	Increase log level"
> +}
> +
> +debug=0
> +while [ $# -gt 0 ]; do
> +	case $1 in
> +		-d|--debug)
> +			debug=$((debug+1))
> +			;;
> +		-h)
> +			help;
> +			exit 0
> +			;;
> +		--)
> +			shift;
> +			break;;
> +		-*)
> +			echo "Unrecognised option: $1";
> +			help;
> +			exit 1
> +			;;
> +		*)
> +			break
> +			;;
> +	esac
> +	shift
> +done
> +
> +[ $debug -gt 0 ] && loglevel=V4L2Compat:0
> +[ $debug -gt 1 ] && loglevel=0
> +[ "$loglevel" != "" ] && export LIBCAMERA_LOG_LEVELS=$loglevel
> +
> +if [ "$LD_PRELOAD" = "" ] ; then
> +   LD_PRELOAD='@LIBCAMERA_V4L2_SO@'
> +else
> +   LD_PRELOAD="$LD_PRELOAD "'@LIBCAMERA_V4L2_SO@'
> +fi
> +
> +export LD_PRELOAD
> +
> +exec "$@"
> diff --git a/src/v4l2/meson.build b/src/v4l2/meson.build
> index f78497b6799b..6e587488cd3a 100644
> --- a/src/v4l2/meson.build
> +++ b/src/v4l2/meson.build
> @@ -33,3 +33,14 @@ 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
> +
> +cdata = configuration_data()
> +cdata.set('LIBCAMERA_V4L2_SO', get_option('prefix') / get_option('libdir') / 'v4l2-compat.so')
> +
> +configure_file(input : 'libcamerify.in',
> +               output : 'libcamerify',
> +               configuration : cdata,
> +               install_dir : get_option('bindir'))
> -- 
> 2.32.0
>