dtboverlay to U-Boot runtime dtb

[Heinrich Schuchardt]

On 7/4/22 14:51, Peter Robinson wrote:
> Hi Peng,
>
>> I did a test to do overlay for U-Boot runtime dtb, but after overlay
>> finish, U-Boot DM driver not work properly because the of_node
>> pointer is changed in a device.
>>
>> So I am thinking whether this is valid to overlay to runtime U-Boot
>> dtb or not. The reason I try this is that I wanna overlay the EFI capsule
>> signature to U-Boot dtb, then capsule update with authentication
>> could work, otherwise I need integrate the signature in dts and
>> rebuild the image. I understand current U-Boot not support
>> overlay U-Boot runtime dtb, just thinking whether this is valid or
>> should we support it.

Applying overlays to the control device-tree is not supported. Allowing
console access on a system where you plan to apply authenticated
capsules seems unwise from a security viewpoint. So we should not
support your scenario.

You can apply overlays to the device-tree passed to the Linux kernel.

Best regards

Heinrich

>
> Bootin did a pretty good blog post for DT overlays in U-Boot, not sure
> if that's useful for this usecase but for reference:
> https://bootlin.com/blog/using-the-u-boot-extension-board-manager-beaglebone-boards-example/