On 1/20/21 11:34 PM, Viresh Kumar wrote: > On 20-01-21, 23:14, Frank Rowand wrote: >> It is a convenient FDT to use because it provides the frame that the overlays >> require to be applied. It is fortunate that fdtoverlay does not reject the use >> of an FDT with overlay metadata as the base blob. > >> This is probably a good idea instead of depending on the leniency of fdtoverlay. > > I believe fdtoverlay allows that intentionally, that would be required > for the cases where we have a hierarchy of extension boards or > overlays. > > A platform can have a base dtb (with /plugin/;), then we can have an > overlay (1) for an extension board (with /plugin/;) and then an > overlay (2) for an extension board for the previous extension board. > > In such a case overlay-(2) can't be applied directly to the base dtb > as it may not find all the nodes it is trying to update. And so > overlay-(2) needs to be applied to overlay-(1) and then the output of > this can be applied to the base dtb. I have only the most surface knowledge of fdtoverlay, mostly from "fdtoverlay --help", but you can apply multiple overlays with a single invocation of fdtoverlay. My _assumption_ was that the overlays would be applied in order, and after any given overlay was applied, subsequent overlays could reference the previously applied overlay. Is my assumption incorrect? > > This is very similar to what I tried with the intermediate.dtb > earlier. >
