Hi,
Upstream kernel commit 88a686728b37 ("kbuild: simplify access to the
kernel's version") [0] extended the Makefile to add the following
defines to the linux/version.h file:
#define LINUX_VERSION_MAJOR $(VERSION)
#define LINUX_VERSION_PATCHLEVEL $(PATCHLEVEL)
#define LINUX_VERSION_SUBLEVEL $(SUBLEVEL)
I would like to have these defines especially LINUX_VERSION_SUBLEVEL
also in older stable kernel versions to make it easier for out of tree
kernel code to detect which version it is compiling against.
In the Linux drivers backports project [1] we backport the current wifi
driver to older Linux versions, so someone with an old kernel can use
current wifi drivers. To make this work we have to know which kernel
version it is being compiled against. The Makefile has access to the
SUBLEVEL variable and can also forward it to the C code, but this does
not work when someone compiles some other driver against the mac80211
subsystem provided by backports for example.
I tried to cherry-pick commit 88a686728b37 to kernel 4.9, but it did not
apply cleanly. Would it get accepted when I just port the changes in the
main Makefile to the currently supported LTS kernel versions?
Hauke
[0]: https://git.kernel.org/linus/88a686728b3739d3598851e729c0e81f194e5c53
[1]: https://backports.wiki.kernel.org/index.php/Main_Page
Here would be my suggestion for kernel 4.9, I haven't tested this yet:
--- a/Makefile
+++ b/Makefile
@@ -1142,7 +1142,10 @@ endef
define filechk_version.h
(echo \#define LINUX_VERSION_CODE $(shell \
expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255); \
- echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))';)
+ echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))';) \
+ echo \#define LINUX_VERSION_MAJOR $(VERSION); \
+ echo \#define LINUX_VERSION_PATCHLEVEL $(PATCHLEVEL); \
+ echo \#define LINUX_VERSION_SUBLEVEL $(SUBLEVEL)
endef
$(version_h): $(srctree)/Makefile FORCE
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