Re: raspi: should vc fixups update properties of existing nodes?

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Jonas,

On 10.04.24 11:59, Jonas Richardsen wrote:
> Hi,
> 
> the function `rpi_vc_fdt_parse` in arch/arm/boards/raspberry-pi/rpi-common.c registers multiple fixups that take over nodes from the video core device tree. These fixups make use of the `of_copy_property` function to copy the properties of the respective node. In the case of already existing nodes (and properties), this function duplicates the properties instead of updating them.

Ouch.

> If the intention is to not override existing properties, one should probably check for the existence of each property before copying to avoid kernel warnings and misconfiguration due to duplicate properties.

I think that's the way to go. of_copy_property should maybe return
PTR_ERR(-EEXIST) if the property already exists. Users are free to
use of_delete_property_by_name beforehand if they want to remove
the content.

> If existing properties are supposed to be updated, this could be achieved by switching to `of_set_property` (or something similar). Note that this notion of overriding properties also exists in video core, see https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/broadcom/bcm2711.dtsi?h=v6.8#n412 for an example.

I think the default should be not to override and exceptions should
be done explicitly.

> I would be glad to submit a patch for either case.

That would be great!

Thanks,
Ahmad

> 
> Regards,
> 
> Jonas
> 
> 
> 

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