We're using honister. We have a recipe that generates a device tree using
devicetree.bbclass. It doesn't do anything special:
SRC_URI = file://system-top.dts
DT_INCLUDE:append = " ${THISDIR}/files"
COMPATIBLE_MACHINE:zynq = "zynq"
inherit devicetree
It's unclear to me how this is actually supposed to work, however. There are no
examples of using the class in poky or meta-openembedded that I can find.
What I'm leaning towards now is creating a bbappend for the kernel recipe that
just installs the generated device tree into arch/arm/boot/dts. But if anyone
has a better way I'd be glad to hear it.
I've done a little more experimenting and I think I understand now. Please
someone correct me if I'm wrong.
If you want an in-tree (kernel source tree, that is) device tree, you set
KERNEL_DEVICETREE. AFAICT the device tree doesn't actually get baked into the
kernel. Rather, it is exported alongside the kernel to be picked up by a
fitImage, for example.
If you want an out-of-tree device tree, you can write a recipe that inherits
devicetree.bbclass (if you want to use the device tree compiler), or I suppose
you could write a recipe that just deploys a pre-built .dtb in a similar way to
how devicetree.bbclass does. Either way, you *don't* set KERNEL_DEVICETREE.
Then the fitimage process will pick up the .dtb.
In my case, I'm creating a fitimage without an initramfs. It's just the kernel
and dtb. This is done by adding this to my MACHINE conf:
KERNEL_CLASSES += "kernel-fitimage"
KERNEL_IMAGETYPES += "fitImage"
You also need to tell the kernel-fitimage.bbclass where to get the dtb from,
which is done somewhat indirectly by setting a preferred provider:
PREFERRED_PROVIDER_virtual/dtb = "my-device-tree"
Thanks,
Chris
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