linux-core Makefile: add GIT_REVISION

This tries to automatically fetch a git revision string and if succeeds,
it #defines GIT_REVISION string macro. Packagers can override it by
'make GIT_REVISION=foo'.

Update Nouveau to use GIT_REVISION, if defined, instead of DRIVER_DATE
in struct drm_driver.

Signed-off-by: Pekka Paalanen <pq@iki.fi>

linux-core/Makefile

@@ -335,6 +335,11 @@ ifneq (,$(findstring i915,$(DRM_MODULES)))
 CONFIG_DRM_I915 := m
 endif
 
+GIT_REVISION := $(shell cd "$(DRMSRCDIR)" && git-describe --abbrev=17)
+ifneq ($(GIT_REVISION),)
+EXTRA_CFLAGS+=-D"GIT_REVISION=\"$(GIT_REVISION)\""
+endif
+
 include $(DRMSRCDIR)/Makefile.kernel
 
 # Depencencies

linux-core/nouveau_drv.c

@@ -86,7 +86,11 @@ static struct drm_driver driver = {
 
 	.name = DRIVER_NAME,
 	.desc = DRIVER_DESC,
+#ifdef GIT_REVISION
+	.date = GIT_REVISION,
+#else
 	.date = DRIVER_DATE,
+#endif
 	.major = DRIVER_MAJOR,
 	.minor = DRIVER_MINOR,
 	.patchlevel = DRIVER_PATCHLEVEL,