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>
---
libfdt/fdt_overlay.c | 197 +++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 175 insertions(+), 22 deletions(-)
diff --git a/libfdt/fdt_overlay.c b/libfdt/fdt_overlay.c
index ceb9687..e6fe058 100644
--- a/libfdt/fdt_overlay.c
+++ b/libfdt/fdt_overlay.c
@@ -39,6 +39,7 @@ static uint32_t overlay_get_target_phandle(const void *fdto, int fragment)
* @fdt: Base device tree blob
* @fdto: Device tree overlay blob
* @fragment: node offset of the fragment in the overlay
+ * @pathp: pointer which receives the path of the target (or NULL)
*
* overlay_get_target() retrieves the target offset in the base
* device tree of a fragment, no matter how the actual targetting is
@@ -49,37 +50,47 @@ static uint32_t overlay_get_target_phandle(const void *fdto, int fragment)
* Negative error code on error
*/
static int overlay_get_target(const void *fdt, const void *fdto,
- int fragment)
+ int fragment, char const **pathp)
{
uint32_t phandle;
- const char *path;
- int path_len;
+ const char *path = NULL;
+ int path_len = 0, ret;
/* Try first to do a phandle based lookup */
phandle = overlay_get_target_phandle(fdto, fragment);
if (phandle == (uint32_t)-1)
return -FDT_ERR_BADPHANDLE;
- if (phandle)
- return fdt_node_offset_by_phandle(fdt, phandle);
+ /* no phandle, try path */
+ if (!phandle) {
+ /* And then a path based lookup */
+ path = fdt_getprop(fdto, fragment, "target-path", &path_len);
+ if (path)
+ ret = fdt_path_offset(fdt, path);
+ else
+ ret = path_len;
+ } else
+ ret = fdt_node_offset_by_phandle(fdt, phandle);
- /* And then a path based lookup */
- path = fdt_getprop(fdto, fragment, "target-path", &path_len);
- if (!path) {
- /*
- * If we haven't found either a target or a
- * target-path property in a node that contains a
- * __overlay__ subnode (we wouldn't be called
- * otherwise), consider it a improperly written
- * overlay
- */
- if (path_len == -FDT_ERR_NOTFOUND)
- return -FDT_ERR_BADOVERLAY;
+ /*
+ * If we haven't found either a target or a
+ * target-path property in a node that contains a
+ * __overlay__ subnode (we wouldn't be called
+ * otherwise), consider it a improperly written
+ * overlay
+ */
+ if (ret < 0 && path_len == -FDT_ERR_NOTFOUND)
+ ret = -FDT_ERR_BADOVERLAY;
+
+ /* return on error */
+ if (ret < 0)
+ return ret;
- return path_len;
- }
+ /* return pointer to path (if available) */
+ if (pathp)
+ *pathp = path ? path : NULL;
- return fdt_path_offset(fdt, path);
+ return ret;
}
/**
@@ -590,7 +601,7 @@ 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.
*
@@ -618,7 +629,7 @@ static int overlay_merge(void *fdt, void *fdto)
if (overlay < 0)
return overlay;
- target = overlay_get_target(fdt, fdto, fragment);
+ target = overlay_get_target(fdt, fdto, fragment, NULL);
if (target < 0)
return target;
@@ -630,6 +641,144 @@ 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;
+ const char *target_path;
+ char *buf;
+ void *p;
+
+ ov_sym = fdt_subnode_offset(fdto, 0, "__symbols__");
+
+ /* if no overlay symbols exist no problem */
+ if (ov_sym < 0)
+ return 0;
+
+ root_sym = fdt_subnode_offset(fdt, 0, "__symbols__");
+
+ /* it no root symbols exist we should create them */
+ if (root_sym < 0) {
+ root_sym = fdt_add_subnode(fdt, 0, "__symbols__");
+ if (root_sym < 0)
+ return root_sym;
+ }
+
+ /* 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;
+
+ /* verify it's a string property (terminated with \0) */
+ if (path_len < 1 || path[path_len - 1] != '\0')
+ return -FDT_ERR_BADVALUE;
+
+ /* format: /<fragment-name>/__overlay__/<relative-subnode-path> */
+
+ if (*path != '/')
+ return -FDT_ERR_BADVALUE;
+
+ /* verify that no stray \0 exist in the property */
+ if (strlen(path) != path_len - 1)
+ 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; safe since "s" lies in \0 terminated prop */
+ 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 */
+ ret = fdt_subnode_offset_namelen(fdto, 0, frag_name,
+ frag_name_len);
+ /* not found? */
+ if (ret < 0)
+ return ret;
+ fragment = ret;
+
+ /* 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, &target_path);
+ if (ret < 0)
+ return ret;
+ target = ret;
+
+ /* if we have a target path use */
+ if (!target_path) {
+ ret = fdt_get_path_len(fdt, target);
+ if (ret < 0)
+ return ret;
+ len = ret;
+ } else
+ len = strlen(target_path);
+
+ ret = fdt_setprop_placeholder(fdt, root_sym, name,
+ len + (len > 1) + rel_path_len + 1, &p);
+ if (ret < 0)
+ return ret;
+
+ /* again in case setprop_placeholder changed it */
+ ret = overlay_get_target(fdt, fdto, fragment, &target_path);
+ if (ret < 0)
+ return ret;
+ target = ret;
+
+ buf = p;
+ if (len > 1) { /* target is not root */
+ if (!target_path) {
+ ret = fdt_get_path(fdt, target, buf, len + 1);
+ if (ret < 0)
+ return ret;
+ } else
+ memcpy(buf, target_path, len + 1);
+
+ } 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 +803,10 @@ 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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