On Wed, May 02, 2018 at 10:19:58AM +0100, Phil Elwell wrote: > David et al., > > I've mentioned before the problem posed for overlays by boolean properties, i.e. > that a boolean property that is "true" in a base DTB cannot be made "false" by an > overlay because doing so requires that the property be deleted. A solution for this > problem would be to define a new FDT tag - FDT_DEL_PROP, say - that is used to encode > any /delete-property/ found in a node during overlay compilation. When the overlay is > applied, the named property would be deleted if present. > > A heuristic would be needed to decide whether this property should be encoded or just > acted on immediately - the use of the '-@' command line parameter would seem to fit the > bill. > > Although one might consider extending this mechanism to cover node deletion, in practice > I think this would be too problematic in terms of broken phandle references etc., and in > most cases 'status = "disabled"' achieves the same objective, so I'm not proposing this > be added. > > Is such a change something you would consider supporting, or do you have an alternative > preferred solution? I'd certainly consider it within the right context. The difficulty is that this obviously requires changing the things that accept the fdt to understand the new format. And if we're going to do that, there's a bunch of other things we should change as well. I've previously had a discussion with Frank Rowand about how we could do a much saner encoding of the fixups using new tags, rather than the currently rather ghastly encoding in special properties and nodes. So maybe add this as one feature to put in a hypothetical v32 (or whatever) fdt format. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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