Re: [OE-core] Build the "boot" partition image (just like the rootfs)

["Stefano Babic" <sbabic@denx.de>]

Hi Mike,

On 15.03.21 14:13, Mike Looijmans wrote:
> For software updates, I want to have what would have gone into the boot 
> partition of the WIC image as a separate file.
> 
> If I want to have the contents of the rootfs as an ext4 image, I can 
> just specify IMAGE_TYPES="ext4" in my image recipe.
>  > This image I can feed to SWUdate and write to the rootfs storage.
> 
> But I also want to be able to update the boot partition (for example, 
> the raspberrypi has the annoying property that devicetree and kernel 
> reside here).

This is very annoying, but you could also get rid of it. You can install 
kernel and device tree in your rootfs (then they are located in /boot as 
usual), and you switch to U-Boot ( RPI_USE_U_BOOT = "1"). The 
proprietary bootloader will start U-Boot instead of kernel, and in 
u-boot you can load kernel and device tree from your rootfs.

> 
> If I create a WIC image, the boot partition is in there with the proper 
> files (from IMAGE_BOOT_FILES) so I would really like to re-use that 
> code. I could create the wic image and then cut out the part I want, but 
> that doesn't seem particularly nice.

You can add vfat support for IMAGE_FSTYPES, and then you can build an 
image (you can just take the files you have in IMAGE_BOOT_FILES).

> 
> What I want to do at update time is to write the new boot partition to 
> another location on disk, and then adjust the partition table to make 
> the first partition entry point to the new copy. That way, in case of 
> unexpected failure (power loss for example), the device remains bootable.

This does not seem to be atomic. It remains the risk that partition 
table gets corrupted and then even the first bootloader cannot run. If 
you want to have a power-cut safe way to update is not enough.

Best regards,
Stefano Babic

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