kernel-devicetree: Introduce KERNEL_DTC_FLAGS to pass dtc flags

Currently DTC_FLAGS kernel makefile parameter can be specified directly on the
command line by adding it to KERNEL_EXTRA_ARGS. However, this prevents
scripts/Makefile.lib logic from appending flags that silence dtc warnings (all
assignments done from within a makefile, to a variable specified on the command
line, are ignored).

Because of this, the do_compile log is cluttered with dtc warnings that should
only be printed when compiling with W="123":
...
/soc: node has a reg or ranges property, but no unit name
/soc/gpu: missing or empty reg/ranges property
/soc/firmware/gpio: missing or empty reg/ranges property
...

To fix this, introduce the dedicated KERNEL_DTC_FLAGS variable to hold
dtc flags and export DTC_FLAGS in the environment before generating the dtbs
(make allows "+=" operations on variables that come from the environment, so
the warnings are silenced properly).

(From OE-Core rev: 2246b0d7a71c69eb2e89c55991d1387069895466)

Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 063b5de86624a42b0aa784db6dddc7552a6dee7f)
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/meta/classes/kernel-devicetree.bbclass b/meta/classes/kernel-devicetree.bbclass
index 81dda8003f..d4f8864200 100644
--- a/meta/classes/kernel-devicetree.bbclass
+++ b/meta/classes/kernel-devicetree.bbclass
@@ -9,6 +9,9 @@ FILES_${KERNEL_PACKAGE_NAME}-image-zimage-bundle = "/${KERNEL_IMAGEDEST}/zImage-
 # Generate kernel+devicetree bundle
 KERNEL_DEVICETREE_BUNDLE ?= "0"
 
+# dtc flags passed via DTC_FLAGS env variable
+KERNEL_DTC_FLAGS ?= ""
+
 normalize_dtb () {
         dtb="$1"
         if echo $dtb | grep -q '/dts/'; then
@@ -50,6 +53,10 @@ do_configure_append() {
 }
 
 do_compile_append() {
+        if [ -n "${KERNEL_DTC_FLAGS}" ]; then
+                export DTC_FLAGS="${KERNEL_DTC_FLAGS}"
+        fi
+
         for dtbf in ${KERNEL_DEVICETREE}; do
                 dtb=`normalize_dtb "$dtbf"`
                 oe_runmake $dtb CC="${KERNEL_CC} $cc_extra " LD="${KERNEL_LD}" ${KERNEL_EXTRA_ARGS}