kbuild: document cc-fullversion

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index bb5306e..e08ef87 100644 (file)
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -501,6 +501,20 @@ more details, with real examples.
        The third parameter may be a text as in this example, but it may also
        be an expanded variable or a macro.
 
+    cc-fullversion
+       cc-fullversion is useful when the exact version of gcc is needed.
+       One typical use-case is when a specific GCC version is broken.
+       cc-fullversion points out a more specific version than cc-version does.
+
+       Example:
+               #arch/powerpc/Makefile
+               $(Q)if test "$(call cc-fullversion)" = "040200" ; then \
+                       echo -n '*** GCC-4.2.0 cannot compile the 64-bit powerpc ' ; \
+                       false ; \
+               fi
+
+       In this example for a specific GCC version the build will error out explaining
+       to the user why it stops.
 
 === 4 Host Program support