apm821xx: build squashfs-rootfs images for the MBL

This patch adds support for squashfs as the root filesystem.

advantages:
 - migrate from a existing -ext4 installation and back
   with the sysupgrade utility
 - existing partition layout will not be lost during switch
 - slightly smaller image size as compared to the -ext4 image.

disadvantages:
 - needs f2fs + tools. This is because fstools rootdisk.c decides based
   on the partition size (currently root partitions > 100 MiB) f2fs is
   used as the rootfs_data filesystem.
 - rootfs_data is placed into the rootfs partition after the squashfs.
   This makes it difficult for tools that expect a /dev/sda${X} device.
   It also makes it difficult for data recovery tools as they might not
   expect to find a embedded partition or will be slightly confused.
   ... or will not support f2fs.

For people with existing build configurations: make sure to include mkf2fs
and f2fsck packages into the image. Otherwise the new -squashfs image will
only boot from the ram-overlay.

Note:
All overlay data (configurations/all installed packages/...) will be
placed in inside the rootfs partition (i.e. /dev/sda2) just after the
squashfs image.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

3 files changed, 7 insertions, 8 deletions

diff --git a/target/linux/apm821xx/image/Makefile b/target/linux/apm821xx/image/Makefile
index 9d9c0e5ace..bfc6562431 100644
--- a/target/linux/apm821xx/image/Makefile
+++ b/target/linux/apm821xx/image/Makefile
@@ -211,7 +211,7 @@ define Build/boot-img
 endef
 
 define Build/hdd-img
-	./mbl_gen_hdd_img.sh $@ $@.boot $(IMAGE_ROOTFS)
+	./mbl_gen_hdd_img.sh $@ $@.boot $(IMAGE_ROOTFS) $(BOOT_SIZE) $(CONFIG_TARGET_ROOTFS_PARTSIZE)
 endef
 
 define Device/wd_mybooklive
@@ -219,7 +219,6 @@ define Device/wd_mybooklive
   DEVICE_PACKAGES := kmod-usb-dwc2 kmod-usb-ledtrig-usbport kmod-usb-storage kmod-fs-vfat wpad-mini
   DEVICE_DTS := wd-mybooklive
   SUPPORTED_DEVICES += mbl wd_mybooklive-duo
-  IMAGE_SIZE := 48m
   BLOCKSIZE := 1k
   DTB_SIZE := 16384
   KERNEL := kernel-bin | dtb | gzip | uImage gzip
@@ -227,7 +226,7 @@ define Device/wd_mybooklive
   BOOT_SIZE := 8
   IMAGES := rootfs.img.gz kernel.dtb
   DEVICE_DTB := apollo3g.dtb
-  FILESYSTEMS := ext4
+  FILESYSTEMS := ext4 squashfs
   IMAGE/kernel.dtb := export-dtb
   IMAGE/rootfs.img.gz := boot-script | boot-img | hdd-img | gzip | append-metadata
 endef
diff --git a/target/linux/apm821xx/image/mbl_boot.scr b/target/linux/apm821xx/image/mbl_boot.scr
index 062dc2725a..955216983b 100644
--- a/target/linux/apm821xx/image/mbl_boot.scr
+++ b/target/linux/apm821xx/image/mbl_boot.scr
@@ -1,4 +1,4 @@
-setenv boot_args 'setenv bootargs root=/dev/sda2 rw rootfstype=ext4'
+setenv boot_args 'setenv bootargs root=/dev/sda2 rw rootfstype=squashfs,ext4'
 setenv load_part1 'sata init; ext2load sata 1:1 ${kernel_addr_r} /boot/uImage; ext2load sata 1:1 ${fdt_addr_r} /boot/apollo3g.dtb'
 setenv load_part2 'sata init; ext2load sata 0:1 ${kernel_addr_r} /boot/uImage; ext2load sata 0:1 ${fdt_addr_r} /boot/apollo3g.dtb'
 setenv load_sata 'if run load_part1; then echo Loaded part 1; elif run load_part2; then echo Loaded part 2; fi'
diff --git a/target/linux/apm821xx/image/mbl_gen_hdd_img.sh b/target/linux/apm821xx/image/mbl_gen_hdd_img.sh
index 589dcf9150..6536ce9872 100755
--- a/target/linux/apm821xx/image/mbl_gen_hdd_img.sh
+++ b/target/linux/apm821xx/image/mbl_gen_hdd_img.sh
@@ -1,16 +1,16 @@
 #!/usr/bin/env bash
 
 set -x
-[ $# -eq 3 ] || {
-    echo "SYNTAX: $0 <file> <bootfs image> <rootfs image>"
+[ $# -eq 5 ] || {
+    echo "SYNTAX: $0 <file> <bootfs image> <rootfs image> <bootfs size> <rootfs size>"
     exit 1
 }
 
 OUTPUT="$1"
 BOOTFS="$2"
 ROOTFS="$3"
-let "BOOTFSSIZE=(`stat -c%s "$2"` + 1048575) / 1048576"
-let "ROOTFSSIZE=(`stat -c%s "$3"` + 1048575) / 1048576"
+BOOTFSSIZE="$4"
+ROOTFSSIZE="$5"
 
 head=4
 sect=63