[PATCH] [RFC] ffmpeg: make LICENSE_FLAGS fine-grained

["Yann Dirson" <yann.dirson@blade-group.com>]

From: Yann Dirson <yann@blade-group.com>

The rationale here is that if the user can only whitelist "commercial"
to use any part of ffmpeg, even it the list of features is carefully
reviewed when switching the whitelisting on, there was nothing to
guard from inadvertently activating a new feature that would not have
been reviewed.

This patch adds one LICENSE_FLAGS value for each feature, except for
those that bring no codec, trying to be on the same level of legal
safety - but then I may miss something.

I tried to leave out of the safe NONCOMMERCIAL_PACKAGECONFIGS list
anything that brings a codec, notably libavcodec.  I also did not look
at non-default features yet.

There may still be a problem if any feature in ffmpeg gets activated
by default upstream and not registed as a PACKAGECONFIG feature.  At
least any of those that depend on another lib would not be enabled,
that could be seen as a sufficient safeguard.
---
 meta/recipes-multimedia/ffmpeg/ffmpeg_4.3.2.bb | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/meta/recipes-multimedia/ffmpeg/ffmpeg_4.3.2.bb b/meta/recipes-multimedia/ffmpeg/ffmpeg_4.3.2.bb
index 08be38ca50..3a36c95151 100644
--- a/meta/recipes-multimedia/ffmpeg/ffmpeg_4.3.2.bb
+++ b/meta/recipes-multimedia/ffmpeg/ffmpeg_4.3.2.bb
@@ -16,7 +16,17 @@ LICENSE_libavutil = "${@bb.utils.contains('PACKAGECONFIG', 'gpl', 'GPLv2+', 'LGP
 LICENSE_libpostproc = "GPLv2+"
 LICENSE_libswresample = "${@bb.utils.contains('PACKAGECONFIG', 'gpl', 'GPLv2+', 'LGPLv2.1+', d)}"
 LICENSE_libswscale = "${@bb.utils.contains('PACKAGECONFIG', 'gpl', 'GPLv2+', 'LGPLv2.1+', d)}"
-LICENSE_FLAGS = "commercial"
+
+# PACKAGECONFIG features that do not pull codecs
+NONCOMMERCIAL_PACKAGECONFIGS = " \
+ alsa bzlib drm gpl lzma zlib xcb xv \
+ avdevice avfilter avformat swresample swscale postproc avresample \
+"
+# An ffmpeg feature not in NONCOMMERCIAL_PACKAGECONFIGS should be explicitly whitelisted.
+# See https://ffmpeg.org/legal.html
+LICENSE_FLAGS = "${@' '.join('commercial_' + cfg \
+                             for cfg in '${PACKAGECONFIG}'.split() \
+                             if cfg not in '${NONCOMMERCIAL_PACKAGECONFIGS}'.split())}"
 
 LIC_FILES_CHKSUM = "file://COPYING.GPLv2;md5=b234ee4d69f5fce4486a80fdaf4a4263 \
                     file://COPYING.GPLv3;md5=d32239bcb673463ab874e80d47fae504 \
-- 
2.30.2