On 23 Jul 2016, at 05:16, Warner Losh <i...@bsdimp.com> wrote: > > On Fri, Jul 22, 2016 at 1:03 AM, David Chisnall <thera...@freebsd.org> wrote: >> On 22 Jul 2016, at 03:40, Warner Losh <i...@bsdimp.com> wrote: >>> >>> On Wed, Jul 20, 2016 at 9:51 AM, David Chisnall <thera...@freebsd.org> >>> wrote: >>>> On 20 Jul 2016, at 16:46, Warner Losh <i...@bsdimp.com> wrote: >>>>> >>>>> I've been trying to get the final spec for it. Right now it's a >>>>> disorganized series >>>>> of patches, some of which have been merge some that haven't. I'll send >>>>> you a >>>>> copy when I can find something better than "here's the code." >>>> >>>> Thanks. From the information I can find, it looks as if most of the >>>> machinery required to implement it is already in dtc, so it should >>>> (hopefully) just be a matter of adding a new keyword to detect plugins, a >>>> scan to find the cross-references (or possibly reusing the existing one) >>>> and then a little bit of extra logic. >>> >>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/overlay-notes.txt >>> has the specs. >> >> Hmm, that’s even less complete than the docs that I’d found. > > Can you share that then?
I only found tutorial-style things: https://www.raspberrypi.org/documentation/configuration/device-tree.md https://learn.adafruit.com/introduction-to-the-beaglebone-black-device-tree/device-tree-overlays I was hoping for something a bit more like a spec. >> From that, it seems as if the only thing that dtc needs to do is support the >> /plugin/ syntax and emit a section describing unresolved references? > > I believe so, yes. That sounds like it should be easy. > >> Or is dtc also expected to be able to do the merging? > > I think that's TBD. We'll need, at the very least, an update libfdt > from upstream that knows how to do the merging, as well as changes to > /boot/loader to be able to pick and choose which plugins to add to the > base. If we can do all that with the BSDL DTC and it passes all the > other GPL test cases, then we may have a winner and we can get started > integrating plugin support to /boot/loader. I know my RPi would be > happier if it had a 'standard' DTB with a plugin for whatever 1-wire > stuff I'm playing with today. Patrick Wildt was running the GPL’d dtc test suite and I fixed all of the things that he reported broken. We’re now using a less-efficient algorithm for calculating the cross-references so that we resolve things in the same order, which makes doing a diff on the dts produced by the two tools easier. David
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