Re: Devicetree add-on

[Sascha Hauer <s.hauer@pengutronix.de>]

Hi Alexander,

On Wed, Jan 29, 2025 at 09:10:58AM +0300, Alexander Shiyan wrote:
> Hello All.
> 
> The question arose whether it is possible to load an add-on into
> devicetree, but NOT through an overlay,
> i.e. as a full-fledged dtb?
> Ideally, it should look like this: the main ENTRY_FUNCTION() loads the
> base tree, then,
> after initialization in device_initcall(), the board modification is
> determined and the full devicetree
> written for this variant is loaded.

exchanging the device tree during runtime is not a good idea. Pointers
from the old tree might still be in use. Also it's not easy to track
which devices have been probed already and which have to be probed from
the new tree. Exchanging the device tree might work at first, but opens
the door for some bad surprises.

Do you need the full device tree in barebox itself or just in the
Kernel? If the latter I would just start the kernel with the full device
tree and keep the original one in barebox.

There are also some boards in the tree in which we use I2C EEPROM
support in PBL, so we can pick the correct device tree from the start
rather than starting with a base device tree.

Sascha

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