kbuild: introduce $(kecho) convenience echo

There is a bunch of places in the build system where we do 'echo' to show
some nice status lines.  This means we still get output when running in
silent mode.  So declare a new KECHO variable that only does 'echo' when we
are in a suitable verbose build mode.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
[sam: added Documentation]
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

Documentation/kbuild/makefiles.txt

@@ -383,6 +383,20 @@ more details, with real examples.
 	to prerequisites are referenced with $(src) (because they are not
 	generated files).
 
+    $(kecho)
+	echoing information to user in a rule is often a good practice
+	but when execution "make -s" one does not expect to see any output
+	except for warnings/errors.
+	To support this kbuild define $(kecho) which will echo out the
+	text following $(kecho) to stdout except if "make -s" is used.
+
+	Example:
+		#arch/blackfin/boot/Makefile
+		$(obj)/vmImage: $(obj)/vmlinux.gz
+			$(call if_changed,uimage)
+			@$(kecho) 'Kernel: $@ is ready'
+
+
 --- 3.11 $(CC) support functions
 
 	The kernel may be built with several different versions of

scripts/Kbuild.include

@@ -24,6 +24,13 @@ basetarget = $(basename $(notdir $@))
 # Escape single quote for use in echo statements
 escsq = $(subst $(squote),'\$(squote)',$1)
 
+###
+# Easy method for doing a status message
+       kecho := :
+ quiet_kecho := echo
+silent_kecho := :
+kecho := $($(quiet)kecho)
+
 ###
 # filechk is used to check if the content of a generated file is updated.
 # Sample usage: