On Wed, 20 Apr 2016 21:50:26 +0200 Johannes Kuhn <[email protected]> wrote:
> figure out how the overlay thing works. As far as I know overlays (CONFIG_OF_OVERLAY) don't work on sunxi. If you want to find out where they are used, grep for "of_overlay_create" (which would create and apply an overlay) in the kernel tree. For comparison, on Raspberry Pi it does work. It has been four months since I looked into it but the following were the problems back then: - dtc (the device tree compiler) didn't support the -@ option for plugins - which you would need. There were patches floating around which didn't cleanly apply which made this work. Just checked 4.6-rc4's dtc - nope, still not in. - the dtc plugin syntax (of the input files, that is) doesn't have consensus - so it's not stable. - the of_changeset_* hotplug functionality (see CONFIG_OF_DYNAMIC) is not specially supported in sunxi either. See also Documentation/devicetree/overlay-notes.txt . There was also an overlay-configfs interface (OF_CONFIGFS), see https://github.com/raspberrypi/linux/commit/54ca6e08ce89f5e33de78db7deff727c12513397 . This one would enable you to use overlays without having a sunxi-specific overlay manager. I just grepped kernel.org 4.6-rc4 - nope, it's not in. (The idea was that you would add an overlay to the kernel by writing it to a mounted configfs filesystem and it would just magically work) I've since given up and just forked and patched the main dts for my configuration - basically searching this mailing list for the right snippets to use. If someone knows some news about this I'd be interested in overlays as well - those would certainly be a cleaner solution for pluggable extension boards than hacking the main dts - if they worked. -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
