devicetree: auto-disable dts for old kernels

After '6392a63 rpi-base.inc: Use KERNEL_DEVICETREE by default' was
introduced, kernel versions < 3.18 might not be buildable. Since full
device tree support was introduced in 3.18 this change ensures that all
kernel < 3.18 will automatically disable device tree.

Signed-off-by: Petter Mabäcker <petter@technux.se>

2 files changed, 48 insertions, 6 deletions

diff --git a/classes/linux-raspberrypi-base.bbclass b/classes/linux-raspberrypi-base.bbclass
new file mode 100644
index 0000000..40beef1
--- /dev/null
+++ b/classes/linux-raspberrypi-base.bbclass
@@ -0,0 +1,39 @@
+inherit linux-kernel-base
+
+
+def get_dts(d, ver):
+    staging_dir = d.getVar("STAGING_KERNEL_BUILDDIR", True)
+    dts = d.getVar("KERNEL_DEVICETREE", True)
+
+    # d.getVar() might return 'None' as a normal string
+    # leading to 'is None' check isn't enough.
+    # TODO: Investigate if this is a bug in bitbake
+    if ver is None or ver == "None":
+        ''' if 'ver' isn't set try to grab the kernel version
+        from the kernel staging '''
+        ver = get_kernelversion_file(staging_dir)
+
+    if ver is not None:
+        min_ver = ver.split('.', 3)
+    else:
+        return dts
+
+    # Always turn off device tree support for kernel's < 3.18
+    try:
+        if int(min_ver[0]) <= 3:
+            if int(min_ver[1]) < 18:
+                dts = ""
+    except IndexError:
+        min_ver = None
+
+    return dts
+
+
+def split_overlays(d, out):
+    dts = get_dts(d, None)
+    if out:
+        overlays = oe.utils.str_filter_out('\S+\-overlay\.dtb$', dts, d)
+    else:
+        overlays = oe.utils.str_filter('\S+\-overlay\.dtb$', dts, d)
+
+    return overlays
diff --git a/classes/sdcard_image-rpi.bbclass b/classes/sdcard_image-rpi.bbclass
index 1ff664d..7592cc1 100644
--- a/classes/sdcard_image-rpi.bbclass
+++ b/classes/sdcard_image-rpi.bbclass
@@ -1,4 +1,5 @@
 inherit image_types
+inherit linux-raspberrypi-base
 
 #
 # Create an image that can by written onto a SD card using dd.
@@ -70,11 +71,6 @@ SDIMG = "${DEPLOY_DIR_IMAGE}/${IMAGE_NAME}.rootfs.rpi-sdimg"
 # Additional files and/or directories to be copied into the vfat partition from the IMAGE_ROOTFS.
 FATPAYLOAD ?= ""
 
-# Device Tree Overlays are assumed to be suffixed by '-overlay.dtb' string and will be put in a dedicated folder
-DT_ALL = "${@d.getVar('KERNEL_DEVICETREE', True) or ''}"
-DT_OVERLAYS = "${@oe.utils.str_filter('\S+\-overlay\.dtb$', '${DT_ALL}', d)}"
-DT_ROOT = "${@oe.utils.str_filter_out('\S+\-overlay\.dtb$', '${DT_ALL}', d)}"
-
 IMAGEDATESTAMP = "${@time.strftime('%Y.%m.%d',time.gmtime())}"
 
 IMAGE_CMD_rpi-sdimg () {
@@ -90,6 +86,9 @@ IMAGE_CMD_rpi-sdimg () {
 
         echo "Creating filesystem with Boot partition ${BOOT_SPACE_ALIGNED} KiB and RootFS ${ROOTFS_SIZE_ALIGNED} KiB"
 
+        # Check if we are building with device tree support
+        DTS="${@get_dts(d, None)}"
+
         # Initialize sdcard image file
         dd if=/dev/zero of=${SDIMG} bs=1024 count=0 seek=${SDIMG_SIZE}
 
@@ -112,7 +111,11 @@ IMAGE_CMD_rpi-sdimg () {
                 mcopy -i ${WORKDIR}/boot.img -s ${DEPLOY_DIR_IMAGE}/${KERNEL_IMAGETYPE}${KERNEL_INITRAMFS}-${MACHINE}.bin ::uImage
                 ;;
         *)
-                if test -n "${KERNEL_DEVICETREE}"; then
+                if test -n "${DTS}"; then
+                        # Device Tree Overlays are assumed to be suffixed by '-overlay.dtb' string and will be put in a dedicated folder
+                        DT_OVERLAYS="${@split_overlays(d, 0)}"
+                        DT_ROOT="${@split_overlays(d, 1)}"
+
                         # Copy board device trees to root folder
                         for DTB in ${DT_ROOT}; do
                                 DTB_BASE_NAME=`basename ${DTB} .dtb`