Re: [PATCH v2 04/18] arm64: dts: m3ulcb-kf: initial device tree

Hi Geert,

On Thu, 2017-09-21 at 11:10 +0200, Geert Uytterhoeven wrote:

Hi Pantelis,

On Thu, Sep 21, 2017 at 10:51 AM, Pantelis Antoniou
[off-list ref] wrote:

quoted

On Wed, 2017-09-20 at 14:32 +0200, Geert Uytterhoeven wrote:

quoted

On Thu, Sep 14, 2017 at 4:18 PM, Vladimir Barinov
[off-list ref] wrote:

quoted

+#include "ulcb-kf.dtsi"

As the Kingfisher is actually an expansion board for H3ULCB (with R-Car H3
ES1.1 and ES2.0) and M3ULCB (with R-Car M3-W), turning ulcb-kf.dtsi into a
DT overlay would make sense.
That would also solve the issue of the 3 extra DTSes needed for all possible
combinations of ULCB and Kingfisher (r8a7795-es1-h3ulcb-kf.dts,
r8a7795-h3ulcb-kf.dts, r8a7796-h3ulcb-kf.dts (perhaps more to follow?)).

But that's too premature, without upstream support for the easy loading of
DT overlays.

Sigh, yes.

quoted

quoted

+/ {
+       model = "Renesas M3ULCB Kingfisher board based on r8a7796";
+       compatible = "shimafuji,kingfisher", "renesas,m3ulcb",
+                    "renesas,r8a7796";
+};

And how to support from an overlay the addition of "shimafuji,kingfisher" to
(not replacement of!) the main compatible value?

You can hack something in DT but it will be gross indeed.

Ideally you'd want a += operator, but it's going to take a lot of
changes starting from DTB blob format.

In yaml we could easily do this with an append tag type

compatible: [ "renesas,m3ulcb", "renesas,r8a7796" ]

compatible: !append "shimafuji,kingfisher"

As we already have /delete-property/, we could add /append-property/ and
/prepend-property/? Would be useful for a .dts including and enhancing
an .dtsi, too.

Yes, that would work on the DTS source level. Doesn't help at runtime.

That doesn't solve the DTB blob format issue yet, though.

Right. The tree and property deletion commands do not have a mapping to
the DTB format. You could add special characters to a property name and
have the overlay application code do something about it.

For instance the original overlay submission did support property and
node deletion by using '-property' & '-node'. Alas it was removed.

quoted

Are you going to be at ELCE? I have a bunch of thing to ask you about
your DT usage patterns.

Yes, and registered for the Device Tree Workshop.

Great. See you then.

Gr{oetje,eeting}s,

                        Geert

Regards

-- Pantelis

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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