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authorArnd Bergmann <arnd@arndb.de>2015-02-18 20:12:42 +0300
committerMauro Carvalho Chehab <mchehab@osg.samsung.com>2015-04-08 21:02:07 +0300
commit9b174527e7b756cda9f5d9e541f87b7fec9cfdf0 (patch)
tree832548b73f17871eff00880b7acef080991aa30a /include/linux
parenta87a4d34286e5f790d2b495db5f37753ef75a80d (diff)
downloadlinux-9b174527e7b756cda9f5d9e541f87b7fec9cfdf0.tar.xz
[media] Add and use IS_REACHABLE macro
In the media drivers, the v4l2 core knows about all submodules and calls into them from a common function. However this cannot work if the modules that get called are loadable and the core is built-in. In that case we get drivers/built-in.o: In function `set_type': drivers/media/v4l2-core/tuner-core.c:301: undefined reference to `tea5767_attach' drivers/media/v4l2-core/tuner-core.c:307: undefined reference to `tea5761_attach' drivers/media/v4l2-core/tuner-core.c:349: undefined reference to `tda9887_attach' drivers/media/v4l2-core/tuner-core.c:405: undefined reference to `xc4000_attach' This was working previously, until the IS_ENABLED() macro was used to replace the construct like #if defined(CONFIG_DVB_CX24110) || (defined(CONFIG_DVB_CX24110_MODULE) && defined(MODULE)) with the difference that the new code no longer checks whether it is being built as a loadable module itself. To fix this, this new patch adds an 'IS_REACHABLE' macro, which evaluates true in exactly the condition that was used previously. The downside of this is that this trades an obvious link error for a more subtle runtime failure, but it is clear that the change that introduced the link error was unintentional and it seems better to revert it for now. Also, a similar change was originally created by Trent Piepho and then reverted by teh change to the IS_ENABLED macro. Ideally Kconfig would be used to avoid the case of a broken dependency, or the code restructured in a way to turn around the dependency, but either way would require much larger changes here. Fixes: 7b34be71db53 ("[media] use IS_ENABLED() macro") See-also: c5dec9fb248e ("V4L/DVB (4751): Fix DBV_FE_CUSTOMISE for card drivers compiled into kernel") Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/kconfig.h9
1 files changed, 9 insertions, 0 deletions
diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h
index be342b94c640..16cfb3448568 100644
--- a/include/linux/kconfig.h
+++ b/include/linux/kconfig.h
@@ -43,4 +43,13 @@
*/
#define IS_MODULE(option) config_enabled(option##_MODULE)
+/*
+ * IS_REACHABLE(CONFIG_FOO) evaluates to 1 if the currently compiled
+ * code can call a function defined in code compiled based on CONFIG_FOO.
+ * This is similar to IS_ENABLED(), but returns false when invoked from
+ * built-in code when CONFIG_FOO is set to 'm'.
+ */
+#define IS_REACHABLE(option) (config_enabled(option) || \
+ (config_enabled(option##_MODULE) && config_enabled(MODULE)))
+
#endif /* __LINUX_KCONFIG_H */