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SWUpdate bring up (I): Install to Yocto Linux and create single copy image

SWUpdate is a popular embedded system update framework. I’m trying to bring up a OTA update system on stm32mp1, and this OTA system will base on SWUpdate. This post records steps need to be done to install SWUpdate system into Yocto Linux, and create a single copy image to test it.

meta-swupdate

SWUpdate was provided to help generate SWUpdate supported images. Clone it to the layers path and add it into conf/bblayers.conf.

Notes:
This layer depends on several recipes in meta-openembedded. i.e. librsync and libubootenv. For STM32MP distribution, the default meta-openembedded version is too old and those recipes are not included yet. To continue, add those recipes manually or reset meta-openembedded to a newer version.

SWUpdate defconfig

defconfig was required by swupdate.inc. Use menuconfig to create one for your boards as defconfig.

Notes:
If CONFIG_WEBSERVER and CONFIG_MONGOOSE was enabled in menuconfig, target boards will run a mongoose webserver so user can access it through <target_ip>:8080 by default

SWUpdate swupdate.cfg

swupdate.cfg will be copied to target as swupdate runtime configurations. In swupdate.cfg we can set board idendity,public-key,suricatta, webserver and even more:

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globals :
{
verbose = true;
loglevel = 5;
syslog = true;
no-downgrading = "1.0.0";
postupdatecmd = "reboot";
};

download :
{
retries = 3;
timeout = 1800;
};

identify : (
{ name = "stm32mp157a-cp"; value = "1.0"; }
);

webserver :
{
document_root = "/www";
userid = 0;
groupid = 0;
}

09-swupdate-args

This file defines extra parameters for swupdate daemon.

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HARDWARE="stm32mp157a-cp:1.0"
CFGFILE="/etc/swupdate.cfg"
SWUPDATE_ARGS="-H ${HARDWARE} -f ${CFGFILE}"

Here we specific hardware information thus SWUpdate daemon will check swu image hardware compatibility before updating. If user trying to use swu image without specific hardware compatibility, SWUpdate will refuse to update.

In boards specific layer, create file swupdate_%.bbappend:

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FILESEXTRAPATHS_append := "${THISDIR}/${PN}:"

PACKAGECONFIG_CONFARGS = ""

SRC_URI += " \
file://swupdate.cfg \
file://09-swupdate-args \
"

do_install_append() {
install -m 0644 ${WORKDIR}/09-swupdate-args ${D}${libdir}/swupdate/conf.d/

install -d ${D}${sysconfdir}
install -m 0644 ${WORKDIR}/swupdate.cfg ${D}${sysconfdir}
}

Now we have structure like this in boards specific layer:

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└── swupdate
├── swupdate
│ ├── 09-swupdate-args
│ ├── defconfig
│ └── swupdate.cfg
└── swupdate_%.bbappend

Install to image

Then we need to add swupdate, swupdate-www and libubootenv-bin into image.

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IMAGE_INSTALL_append = " swupdate swupdate-www libubootenv-bin"

Flash the built image to target, make sure PC and target board are in same LAN, then we can access <target_ip>:8080 :

Create a single copy update image for test

Now it’s time to create a swu image to test SWUpdate system.

sw-description

sw-description defines the compatibility and usage of swu images. Here we defined a single copy update image, which is compatible with boards stm32mp157a-cp and will update target rootfs:

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software =
{
version = "1.0.0";

stm32mp157a-cp = {
hardware-compatibility: [ "1.0" ];
images: (
{
filename = "cp-image-core-openstlinux-eglfs-stm32mp1-cp.ext4.gz";
type = "raw";
sha256 = "@cp-image-core-openstlinux-eglfs-stm32mp1-cp.ext4.gz";
installed-directly = true;
compressed = true;
device = "/dev/mmcblk0p6";
}
);
};
}

Recipe for update image

To generate a swu file from bitbake, we need to create a recipe for update image. In my scenario it was named as cp-image-update.bb :

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DESCRIPTION = "SWUpdate compound image"

LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"

inherit swupdate

SRC_URI = " \
file://sw-description \
"

# images to build before building swupdate image
IMAGE_DEPENDS = "cp-image-core"

# images and files that will be included in the .swu image
SWUPDATE_IMAGES = "cp-image-core-openstlinux-eglfs-stm32mp1-cp"

SWUPDATE_IMAGES_FSTYPES[cp-image-core-openstlinux-eglfs-stm32mp1-cp] = ".ext4.gz"

Now we have structure like this in boards specific layer:

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.
├── images
│ ├── cp-image-update
│ │ └── sw-description
│ └── cp-image-update.bb

To generate swu image, call bitbake cp-image-update.

Generate update image without image recipe

Sometimes we want to generate a swu image for test purpose, in this scenario we can skip bitbake and use a simple shell script to generate swu image quickly:

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#!/bin/sh

CONTAINER_VER="1.0"
PRODUCT_NAME="stm32mp157-cp"
FILES="sw-description cp-image-core-openstlinux-eglfs-stm32mp1-cp.ext4.gz"
for i in $FILES;do
echo $i;done | cpio -ov -H crc > ${PRODUCT_NAME}_${CONTAINER_VER}.swu

Quick check structure of generated swu image

Since swu image was cpio based, we can use cat to check structure of it:

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cat cp-image-update-openstlinux-eglfs-stm32mp1-cp.swu | cpio -it
sw-description
cp-image-core-openstlinux-eglfs-stm32mp1-cp.ext4.gz
88360 blocks

Test with generated swu image on target

Use web interface

We can trigger update easily by uploading swu image through webserver:

We defined postupdatecmd = "reboot"; in swupdate.cfg, so system will automatically reboot:

Use command line interface

We also can use command line to trigger update if we have an usb drive which contains swu image and has connected to target:

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swupdate -i /media/cp-image-update-openstlinux-eglfs-stm32mp1-cp.swu -H stm32mp157a-cp:1.0