As an example, to illustrate potential pain points we will use a Versatile
Express CortexA9x4 board, emulated under QEMU (vexpress-a9 target). The board
comes with 128MB of CFI NOR flash, provided in form of 2 * 64MB dies. Respective
details may slightly differ for NAND flash or SPI NOR flash devices.
It is possible to build a Yocto image and inspect all the details of Mender
integration by adding the meta-mender-qemu layer to the build. The layer
defines a vexpress-qemu-flash machine and includes all necessary pieces to
enable MTD and UBI support.
Testing raw flash support under QEMU requires version >= 2.9 (see the output
of qemu-system-arm --version command). Earlier versions contain a bug in
CFI flash support that renders flash support on vexpress-a9 unusable.
Add the following to local.conf and run bitbake core-image-minimal:
INHERIT += "mender-full-ubi"
...
MACHINE = "vexpress-qemu-flash"
A successful build will produce a vexpress-nor image in ${DEPLOYDIR}:
$ ls -shLl tmp/deploy/images/vexpress-qemu-flash/core-image-minimal-vexpress-qemu-flash.vexpress-nor
129M -rw-r--r-- 2 user user 129M 07-18 15:34 tmp/deploy/images/vexpress-qemu-flash/core-image-minimal-vexpress-qemu-flash.vexpress-norA vexpress-nor image is a tar file that contains an image for each of the
nor 'drives' emulated by QEMU. It is specific to QEMU and will not
generally be used for other devices, which will usually use either ubimg
or mtdimg.
The image can be run by calling a mender-qemu helper script provided in
meta-mender-qemu layer:
QEMU_SYSTEM_ARM=$HOME/qemu-install/bin/qemu-system-arm \
DISK_IMG=tmp/deploy/images/vexpress-qemu-flash/core-image-minimal-vexpress-qemu-flash.vexpress-nor \
MACHINE=vexpress-qemu-flash \
../meta-mender/meta-mender-qemu/scripts/mender-qemuThe QEMU_SYSTEM_ARM environment variable can optionally provide a path to
qemu-system-arm binary used by the script. When empty or not defined, the
script will call qemu-system-arm available in your $PATH.
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