fdt: Allow stacked overlays phandle references
authorPantelis Antoniou <pantelis.antoniou@konsulko.com>
Mon, 4 Sep 2017 20:12:13 +0000 (23:12 +0300)
committerSimon Glass <sjg@chromium.org>
Fri, 15 Sep 2017 11:27:48 +0000 (05:27 -0600)
commitf00c36a01e774dea1ed2a1171da9e372610ee8eb
tree0e41dbc9089430a7b3545979c8243f3edc3a651a
parent81ecc5d92badfcf1415a6052b5896a62271a94dc
fdt: Allow stacked overlays phandle references

This patch enables an overlay to refer to a previous overlay's
labels by performing a merge of symbol information at application
time.

In a nutshell it allows an overlay to refer to a symbol that a previous
overlay has defined. It requires both the base and all the overlays
to be compiled with the -@ command line switch so that symbol
information is included.

base.dts
--------

/dts-v1/;
/ {
foo: foonode {
foo-property;
};
};

$ dtc -@ -I dts -O dtb -o base.dtb base.dts

bar.dts
-------

/dts-v1/;
/plugin/;
/ {
fragment@1 {
target = <&foo>;
__overlay__ {
overlay-1-property;
bar: barnode {
bar-property;
};
};
};
};

$ dtc -@ -I dts -O dtb -o bar.dtb bar.dts

baz.dts
-------

/dts-v1/;
/plugin/;
/ {
fragment@1 {
target = <&bar>;
__overlay__ {
overlay-2-property;
baz: baznode {
baz-property;
};
};
};
};

$ dtc -@ -I dts -O dtb -o baz.dtb baz.dts

Applying the overlays:

$ fdtoverlay -i base.dtb -o target.dtb bar.dtb baz.dtb

Dumping:

$ fdtdump target.dtb
/ {
            foonode {
                overlay-1-property;
                foo-property;
                linux,phandle = <0x00000001>;
                phandle = <0x00000001>;
                barnode {
                    overlay-2-property;
                    phandle = <0x00000002>;
                    linux,phandle = <0x00000002>;
                    bar-property;
                    baznode {
                        phandle = <0x00000003>;
                        linux,phandle = <0x00000003>;
                        baz-property;
                    };
                };
            };
            __symbols__ {
                baz = "/foonode/barnode/baznode";
                bar = "/foonode/barnode";
                foo = "/foonode";
            };
};

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Simon Glass <sjg@chromium.org>
lib/libfdt/fdt_overlay.c