fng-install: Add overlay via gfxml2to

Using the new approach of the `guf-prepare-kernel.sh` we can now
manipulate the kernel device tree during installation time.

This makes it possible to overlay the base kernel device tree with device
specific device tree overlay blobs. As a result we can configure the
kernel in a device specific way on installation using a chroot
approach.

One approach to create the device specific overlay is to create it from
the established Garz & Fricke XML files. This is done by the new tool
`gfxml2dtbo`. The tool is not finished and polished yet however it
might be of use already and the usage in the install script will enable
us to faster develop the tool further.

To be able to get the XML file that is normally residing in
`/etc/shared` we need to mount it first.

recipes-bsp/fng-install/files/mx6/fng-install.sh

@@ -657,10 +657,13 @@ mounttarget()
     mount -o bind /tmp $TARGETROOT/var/tmp
 
     mkdir -p $TARGETROOT/var/tmp
+    
+    mkdir -p $TARGETROOT/etc/shared
 
     mount -t proc proc ${TARGETROOT}/proc/
     mount -t sysfs sys ${TARGETROOT}/sys/
     mount -o bind /dev ${TARGETROOT}/dev/
+    mount -o ro,bind /etc/shared ${TARGETROOT}/etc/shared
 }
 
 #===========================================================
@@ -670,6 +673,7 @@ mounttarget()
 unmounttarget()
 {
     set +o pipefail
+    umount $TARGETROOT/etc/shared || true
     umount $TARGETROOT/var/tmp || true
     umount $TARGETROOT/tmp || true
     umount $ABSTARGETTMP || true

recipes-bsp/fng-install/files/mx6/guf-prepare-kernel.sh

@@ -7,6 +7,8 @@
 
 KERNEL_FILE=$1
 DEVICETREE_FILE=$2
+shift 2
+DEVICETREE_OVERLAYS=$*
 
 # Make sure we have access to the bootpartition
 BOOTPARTITION=/dev/mmcblk0p2
@@ -15,21 +17,6 @@ MOUNTPOINT=/boot
 #========================================================
 # helper functions
 #========================================================
-string_contains()
-{
-    case "$1" in
-        *$2*) return 0
-    esac
-    return 1
-}
-string_ends_with()
-{
-    case "$1" in
-        *$2) return 0
-    esac
-    return 1
-}
-
 get_platform()
 {
     # Determine platform in order to choose devicetree
@@ -108,17 +95,14 @@ fi
 
 if [ -z "$DEVICETREE_FILE" ]
 then
-    # Read default devicetree file from boot partitione
+    # Read default devicetree file from boot partition
     if [ -r "$MOUNTPOINT"/devicetree ]
     then
         DEVICETREE_FILE="$( head -n 1 "$MOUNTPOINT"/devicetree )"
     else
         PLATFORM="$( get_platform )"
-        for dtb in "$MOUNTPOINT/"*.dtb ; do
-            if string_ends_with "$dtb" "$PLATFORM.dtb"
-            then
-                DEVICETREE_FILE="$(basename "$dtb")"
-            fi
+        for dtb in "$MOUNTPOINT/"*"$PLATFORM.dtb" ; do
+            DEVICETREE_FILE="$(basename "$dtb")"
         done
 
         if [ -z "$DEVICETREE_FILE" ]; then
@@ -138,14 +122,31 @@ fi
 # Mark the currently selected devicetree as the one
 # (we are on fat, so we use a textfile instead of links):
 echo "${DEVICETREE_FILE}" > "${MOUNTPOINT}/devicetree"
+DEVICETREE_APPEND_FILE=$DEVICETREE_FILE
 # Store default kernel file for later usage
 echo "$KERNEL_FILE" > "$MOUNTPOINT"/kernel
 
+if [ -x "/usr/bin/gfxml2dto" ]
+then
+    # Create overlay form G&F XML
+    if gfxml2dto -o "$MOUNTPOINT"/gfxml-overlay.dtbo 
+    then
+        DEVICETREE_OVERLAYS="$MOUNTPOINT/gfxml-overlay.dtbo $DEVICETREE_OVERLAYS"
+    fi
+fi
+
+if [ -n "$DEVICETREE_OVERLAYS" ] && [ -x "/usr/bin/fdtoverlay" ]
+then
+# shellcheck disable=SC2086
+    if fdtoverlay -i "$MOUNTPOINT/$DEVICETREE_FILE" -o "${MOUNTPOINT}/devicetree.dtb" $DEVICETREE_OVERLAYS
+    then
+        echo $DEVICETREE_OVERLAYS > ${MOUNTPOINT}/overlays
+        DEVICETREE_APPEND_FILE="${MOUNTPOINT}/devicetree.dtb"
+    fi
+fi
+
 # Combine both to one file called linuximage
-cat "$MOUNTPOINT/$KERNEL_FILE" "$MOUNTPOINT/$DEVICETREE_FILE" > "$MOUNTPOINT"/linuximage
-# Store the selected kernel
-echo "$KERNEL_FILE" > "$MOUNTPOINT"/kernel
-echo "$DEVICETREE_FILE" > "$MOUNTPOINT"/devicetree
+cat "$MOUNTPOINT/$KERNEL_FILE" "$DEVICETREE_APPEND_FILE" > "$MOUNTPOINT"/linuximage
 
 sync
 if $MOUNTED