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@xxxxxxxxxxxx>
---
.gitignore | 1 +
libfdt/fdt_overlay.c | 131 ++++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 131 insertions(+), 1 deletion(-)
diff --git a/.gitignore b/.gitignore
index 545b899..f333c28 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,3 +15,4 @@ lex.yy.c
/fdtput
/patches
/.pc
+/fdtoverlay
diff --git a/libfdt/fdt_overlay.c b/libfdt/fdt_overlay.c
index ceb9687..fb17ef2 100644
--- a/libfdt/fdt_overlay.c
+++ b/libfdt/fdt_overlay.c
@@ -590,7 +590,7 @@ static int overlay_apply_node(void *fdt, int target,
*
* overlay_merge() merges an overlay into its base device tree.
*
- * This is the final step in the device tree overlay application
+ * This is the next to last step in the device tree overlay application
* process, when all the phandles have been adjusted and resolved and
* you just have to merge overlay into the base device tree.
*
@@ -630,6 +630,131 @@ static int overlay_merge(void *fdt, void *fdto)
return 0;
}
+/**
+ * overlay_symbol_update - Update the symbols of base tree after a merge
+ * @fdt: Base Device Tree blob
+ * @fdto: Device tree overlay blob
+ *
+ * overlay_symbol_update() updates the symbols of the base tree with the
+ * symbols of the applied overlay
+ *
+ * This is the last step in the device tree overlay application
+ * process, allowing the reference of overlay symbols by subsequent
+ * overlay operations.
+ *
+ * returns:
+ * 0 on success
+ * Negative error code on failure
+ */
+static int overlay_symbol_update(void *fdt, void *fdto)
+{
+ int root_sym, ov_sym, prop, path_len, fragment, target;
+ int len, frag_name_len, ret, rel_path_len;
+ const char *s;
+ const char *path;
+ const char *name;
+ const char *frag_name;
+ const char *rel_path;
+ char *buf;
+ void *p;
+
+ root_sym = fdt_subnode_offset(fdt, 0, "__symbols__");
+ ov_sym = fdt_subnode_offset(fdto, 0, "__symbols__");
+
+ /* if neither exist we can't update symbols, but that's OK */
+ if (root_sym < 0 || ov_sym < 0)
+ return 0;
+
+
+ /* iterate over each overlay symbol */
+ fdt_for_each_property_offset(prop, fdto, ov_sym) {
+
+ path = fdt_getprop_by_offset(fdto, prop, &name, &path_len);
+ if (!path)
+ return path_len;
+
+ /* skip autogenerated properties */
+ if (!strcmp(name, "name"))
+ continue;
+
+ /* format: /<fragment-name>/__overlay__/<relative-subnode-path> */
+
+ if (*path != '/')
+ return -FDT_ERR_BADVALUE;
+
+ /* get fragment name first */
+ s = strchr(path + 1, '/');
+ if (!s)
+ return -FDT_ERR_BADVALUE;
+
+ frag_name = path + 1;
+ frag_name_len = s - path - 1;
+
+ /* verify format */
+ len = strlen("/__overlay__/");
+ if (strncmp(s, "/__overlay__/", len))
+ return -FDT_ERR_NOTFOUND;
+
+ rel_path = s + len;
+ rel_path_len = strlen(rel_path);
+
+ /* find the fragment index in which the symbol lies */
+ fdt_for_each_subnode(fragment, fdto, 0) {
+
+ s = fdt_get_name(fdto, fragment, &len);
+ if (!s)
+ continue;
+
+ /* name must match */
+ if (len == frag_name_len && !memcmp(s, frag_name, len))
+ break;
+ }
+
+ /* not found? */
+ if (fragment < 0)
+ return -FDT_ERR_NOTFOUND;
+
+ /* an __overlay__ subnode must exist */
+ ret = fdt_subnode_offset(fdto, fragment, "__overlay__");
+ if (ret < 0)
+ return ret;
+
+ /* get the target of the fragment */
+ ret = overlay_get_target(fdt, fdto, fragment);
+ if (ret < 0)
+ return ret;
+ target = ret;
+
+ len = fdt_get_path_len(fdt, target);
+
+ ret = fdt_setprop_alloc(fdt, root_sym, name,
+ len + (len > 1) + rel_path_len + 1, &p);
+ if (ret < 0)
+ return ret;
+
+ /* again in case setprop_alloc changed it */
+ ret = overlay_get_target(fdt, fdto, fragment);
+ if (ret < 0)
+ return ret;
+ target = ret;
+
+ buf = p;
+ if (len > 1) { /* target is not root */
+ ret = fdt_get_path(fdt, target, buf, len + 1);
+ if (ret < 0)
+ return ret;
+
+ } else
+ len--;
+
+ buf[len] = '/';
+ memcpy(buf + len + 1, rel_path, rel_path_len);
+ buf[len + 1 + rel_path_len] = '\0';
+ }
+
+ return 0;
+}
+
int fdt_overlay_apply(void *fdt, void *fdto)
{
uint32_t delta = fdt_get_max_phandle(fdt);
@@ -654,6 +779,10 @@ int fdt_overlay_apply(void *fdt, void *fdto)
if (ret)
goto err;
+ ret = overlay_symbol_update(fdt, fdto);
+ if (ret)
+ goto err;
+
/*
* The overlay has been damaged, erase its magic.
*/
--
2.1.4
--
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