From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Elwell Subject: Overlays and boolean properties Date: Tue, 29 Nov 2016 13:06:16 +0000 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Sender: devicetree-compiler-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: David Gibson , Pantelis Antoniou , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Devicetree Compiler List-Id: devicetree@vger.kernel.org Boolean properties are defined as being properties with no content, that are true if present and false if absent. They pose a problem for DT overlays, since the proposed (and widely used) overlay mechanism does not allow for properties (or nodes) to be deleted; overlays can only make a false property true, so boolean properties are effectively monostable - once true they become immutable. The standard DT syntax includes /delete-property/ and /delete-node/ directives that do what you would expect from their names, but that facility is not available to overlays. There is no FDT node that represents the deletion - the directives are acted on immediately - so we would need some extra markup - say __delete_property__ and __delete_node__ - to hold the names of items to be deleted. Before I take this further, does anybody have any thoughts on the idea? Phil