Hi, sorry for the delay on this patchset. On 24-03-25, Sascha Hauer wrote: > Hi Marco, > > On Fri, Mar 22, 2024 at 05:49:47PM +0100, Marco Felsch wrote: > > The FIT spec is not very specific when it comes to device-tree overlay > > handling. > > By FIT spec you mean > https://github.com/u-boot/u-boot/blob/master/doc/usage/fit/overlay-fdt-boot.rst, > right, or is there more? this is just an example which is not complete e.g. it misses the signature node in case of verified boot. I used [1] as reference but after reading it again I see that this reference list the kernel or firmware properties as mandatory. [1] https://docs.u-boot.org/en/latest/usage/fit/source_file_format.html#configurations-node > > Overlays can be added directely to an config node: > > > > config-a { > > compatible = "machine-compatible"; > > kernel = "kernel-img-name"; > > fdt = "fdt-base-name", "fdt-overlay1-name", "..."; > > } > > > > or they are supplied via dedicated config nodes: > > > > overlay-2 { > > fdt = "fdt-overlay2-name"; > > } > > > > Of course these config nodes can have compatibles as well: > > > > overlay-3 { > > compatible = "machine-compatible"; > > fdt = "fdt-overlay3-name"; > > } > > The text I referenced above doesn't mention compatible properties in > overlay config nodes. You're right, but the format description chapter [1] does. > > The current fit_find_compatible_unit() code would skip the overlay node > > if the config-a compatible has the same score as the overlay-3 > > compatible and if the overlay-3 config-node is listed after the config-a > > config-node. But if the compatible of config-a config-node has a lower > > score or the overlay-3 config-note is listed first (the spec does not > > specify any order) we end up in taking the overlay-3 config-node instead > > of config-a config-node. > > You could distinguish overlay config nodes from full config nodes by the > presence of a "kernel" property. Overlay config nodes do not have it. Of course this could be done but I wanted to make it more explicit since the FIT spec is not very clear when it comes to overlays. Instead of adding an explicit image type like: - type = "flat_dt_overlay"; they used the already existing definitions. Therefore I went this way so it is up to user to specify the overlay config nodes explicit. Regards, Marco > > Sascha > > -- > Pengutronix e.K. | | > Steuerwalder Str. 21 | http://www.pengutronix.de/ | > 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | > Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | >
