[OE-core] How about deploying devicetree (dtb) files?

[Mike Looijmans]

Now that the subject came up, maybe it's good to exchange some ideas here.

Building the DTB is one thing. But we have to get it on the target as well.

Currently, a bitbake virtual/kernel will also build one or more dtb 
files, and put them in the directory where the images will end up. It's 
up to the user to make it so that the blobs actually get programmed onto 
the target. Nothing wrong with that.

At some point, I thought it would be a good idea to be able to upgrade 
boards "in the field". So I added a postinstall script to the kernel to 
deploy in "/tmp/boot" instead of "/boot" and then make it write itself 
into the flash device or onto the FAT partition on the SD card, or 
whatever other method I came up with to load the kernel.

Now for the devicetree, I thought I could just include the 
"kernel-devicetree" package onto my system, add a bit of script, and 
that would allow me to have devices upgrade themselves.

The "kernel-devicetree" package contains multiple DTB files. I would 
expect a target to actually use only one, and that the various dtb files 
are intended for different targets. I think it would make sense to split 
that single package into a package for each DTB file. Then you can pick 
and choose which dtb you want on your target.

Another issue is that the kernel-devicetree package postinstall script 
calls "awk" and "update-alternatives". Those must therefore be present 
on the target, if you expect to be able to install or upgrade it. As far 
as I can see, the only reason for using these tools is to create a 
symbolic link. As far as I know, no other package provides a dtb file. 
So why is it registering itself as an alternative?

And I was just wondering, how do you guys handle upgrading kernel, 
bootloader and devicetree files?


Met vriendelijke groet / kind regards,

Mike Looijmans

TOPIC Embedded Systems
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E-mail: mike.looijmans at topic.nl
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