6 files changed, 616 insertions, 3 deletions

diff --git a/sys/boot/fdt/Makefile b/sys/boot/fdt/Makefile
index 22d8da59655e8..ce11dbb42f841 100644
--- a/sys/boot/fdt/Makefile
+++ b/sys/boot/fdt/Makefile
@@ -10,7 +10,7 @@ SRCS+=		fdt.c fdt_ro.c fdt_wip.c fdt_sw.c fdt_rw.c fdt_strerror.c \
 		fdt_empty_tree.c
 
 # Loader's fdt commands extension sources.
-SRCS+=		fdt_loader_cmd.c
+SRCS+=		fdt_loader_cmd.c fdt_overlay.c
 
 CFLAGS+=	-I${.CURDIR}/../../contrib/libfdt/ -I${.CURDIR}/../common/
 
diff --git a/sys/boot/fdt/fdt_loader_cmd.c b/sys/boot/fdt/fdt_loader_cmd.c
index 8cd8ab50150e8..6983a599a5d03 100644
--- a/sys/boot/fdt/fdt_loader_cmd.c
+++ b/sys/boot/fdt/fdt_loader_cmd.c
@@ -39,6 +39,7 @@ __FBSDID("$FreeBSD$");
 
 #include "bootstrap.h"
 #include "fdt_platform.h"
+#include "fdt_overlay.h"
 
 #ifdef DEBUG
 #define debugf(fmt, args...) do { printf("%s(): ", __func__);	\
@@ -276,6 +277,128 @@ fdt_load_dtb_file(const char * filename)
 	return (0);
 }
 
+static int
+fdt_load_dtb_overlay(const char * filename)
+{
+	struct preloaded_file *bfp, *oldbfp;
+	struct fdt_header header;
+	int err;
+
+	debugf("fdt_load_dtb_overlay(%s)\n", filename);
+
+	oldbfp = file_findfile(filename, "dtbo");
+
+	/* Attempt to load and validate a new dtb from a file. */
+	if ((bfp = file_loadraw(filename, "dtbo", 1)) == NULL) {
+		printf("failed to load file '%s'\n", filename);
+		return (1);
+	}
+
+	COPYOUT(bfp->f_addr, &header, sizeof(header));
+	err = fdt_check_header(&header);
+
+	if (err < 0) {
+		file_discard(bfp);
+		if (err == -FDT_ERR_BADVERSION)
+			printf("incompatible blob version: %d, should be: %d\n",
+			    fdt_version(fdtp), FDT_LAST_SUPPORTED_VERSION);
+
+		else
+			printf("error validating blob: %s\n",
+			    fdt_strerror(err));
+		return (1);
+	}
+
+	/* A new dtb was validated, discard any previous file. */
+	if (oldbfp)
+		file_discard(oldbfp);
+
+	return (0);
+}
+
+int
+fdt_load_dtb_overlays(const char * filenames)
+{
+	char *names;
+	char *name;
+	char *comaptr;
+
+	debugf("fdt_load_dtb_overlay(%s)\n", filenames);
+
+	names = strdup(filenames);
+	if (names == NULL)
+		return (1);
+	name = names;
+	do {
+		comaptr = strchr(name, ',');
+		if (comaptr)
+			*comaptr = '\0';
+		fdt_load_dtb_overlay(name);
+		name = comaptr + 1;
+	} while(comaptr);
+
+	free(names);
+	return (0);
+}
+
+void
+fdt_apply_overlays()
+{
+	struct preloaded_file *fp;
+	size_t overlays_size, max_overlay_size, new_fdtp_size;
+	void *new_fdtp;
+	void *overlay;
+	int rv;
+
+	if ((fdtp == NULL) || (fdtp_size == 0))
+		return;
+
+	overlays_size = 0;
+	max_overlay_size = 0;
+	for (fp = file_findfile(NULL, "dtbo"); fp != NULL; fp = fp->f_next) {
+		if (max_overlay_size < fp->f_size)
+			max_overlay_size = fp->f_size;
+		overlays_size += fp->f_size;
+	}
+
+	/* Nothing to apply */
+	if (overlays_size == 0)
+		return;
+
+	/* It's actually more than enough */
+	new_fdtp_size = fdtp_size + overlays_size;
+	new_fdtp = malloc(new_fdtp_size);
+	if (new_fdtp == NULL) {
+		printf("failed to allocate memory for DTB blob with overlays\n");
+		return;
+	}
+
+	overlay = malloc(max_overlay_size);
+	if (overlay == NULL) {
+		printf("failed to allocate memory for DTB blob with overlays\n");
+		free(new_fdtp);
+		return;
+	}
+
+	rv = fdt_open_into(fdtp, new_fdtp, new_fdtp_size);
+	if (rv != 0) {
+		printf("failed to open DTB blob for applying overlays\n");
+		return;
+	}
+
+	for (fp = file_findfile(NULL, "dtbo"); fp != NULL; fp = fp->f_next) {
+		printf("applying DTB overlay '%s'\n", fp->f_name);
+		COPYOUT(fp->f_addr, overlay, fp->f_size);
+		fdt_overlay_apply(new_fdtp, overlay, fp->f_size);
+	}
+
+	free(fdtp);
+	fdtp = new_fdtp;
+	fdtp_size = new_fdtp_size;
+
+	free(overlay);
+}
+
 int
 fdt_setup_fdtp()
 {
diff --git a/sys/boot/fdt/fdt_overlay.c b/sys/boot/fdt/fdt_overlay.c
new file mode 100644
index 0000000000000..a19f06e8e9477
--- /dev/null
+++ b/sys/boot/fdt/fdt_overlay.c
@@ -0,0 +1,438 @@
+/*-
+ * Copyright (c) 2015 Oleksandr Tymoshenko <gonzo@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <stand.h>
+#include <libfdt.h>
+
+#include "fdt_overlay.h"
+
+/*
+ * Get max phandle
+ */
+static uint32_t
+fdt_max_phandle(void *fdtp)
+{
+	int o, depth;
+	uint32_t max_phandle, phandle;
+
+	depth = 1;
+	o = fdt_path_offset(fdtp, "/");
+	max_phandle = fdt_get_phandle(fdtp, o);
+	for (depth = 0; (o >= 0) && (depth >= 0); o = fdt_next_node(fdtp, o, &depth)) {
+		phandle = fdt_get_phandle(fdtp, o);
+		if (max_phandle < phandle)
+			max_phandle = phandle;
+	}
+
+	return max_phandle;
+}
+
+/*
+ * Returns exact memory location specified by fixup in format
+ * /path/to/node:property:offset
+ */
+static void *
+fdt_get_fixup_location(void *fdtp, const char *fixup)
+{
+	char *path, *prop, *offsetp, *endp;
+	int prop_offset, o, proplen;
+	void  *result;
+
+	result = 0;
+
+	path = strdup(fixup);
+	prop = strchr(path, ':');
+	if (prop == NULL) {
+		printf("missing property part in \"%s\"\n", fixup);
+		result = NULL;
+		goto out;
+	}
+
+	*prop = 0;
+	prop++;
+
+	offsetp = strchr(prop, ':');
+	if (offsetp == NULL) {
+		printf("missing offset part in \"%s\"\n", fixup);
+		result = NULL;
+		goto out;
+	}
+
+	*offsetp = 0;
+	offsetp++;
+
+	prop_offset = strtoul(offsetp, &endp, 10);
+	if (*endp != '\0') {
+		printf("\"%s\" is not valid number\n", offsetp);
+		result = NULL;
+		goto out;
+	}
+
+	o = fdt_path_offset(fdtp, path);
+	if (o < 0) {
+		printf("path \"%s\" not found\n", path);
+		result = NULL;
+		goto out;
+	}
+
+	result = fdt_getprop_w(fdtp, o, prop, &proplen);
+	if (result == NULL){
+		printf("property \"%s\" not found in  \"%s\" node\n", prop, path);
+		result = NULL;
+		goto out;
+	}
+
+	if (proplen < prop_offset + sizeof(uint32_t)) {
+		printf("%s: property length is too small for fixup\n", fixup);
+		result = NULL;
+		goto out;
+	}
+
+	result = (char*)result + prop_offset;
+
+out:
+	free(path);
+	return (result);
+}
+
+/*
+ * Process one entry in __fixups__ { } node
+ * @fixups is property value, array of NUL-terminated strings
+ *   with fixup locations
+ * @fixups_len length of the fixups array in bytes
+ * @phandle is value for these locations
+ */
+static int
+fdt_do_one_fixup(void *fdtp, const char *fixups, int fixups_len, int phandle)
+{
+	void *fixup_pos;
+	uint32_t val;
+
+	val = cpu_to_fdt32(phandle);
+
+	while (fixups_len > 0) {
+		fixup_pos = fdt_get_fixup_location(fdtp, fixups);
+		if (fixup_pos != NULL)
+			memcpy(fixup_pos, &val, sizeof(val));
+
+		fixups_len -= strlen(fixups) + 1;
+		fixups += strlen(fixups) + 1;
+	}
+
+	return (0);
+}
+
+/*
+ * Increase u32 value at pos by offset
+ */
+static void
+fdt_increase_u32(void *pos, uint32_t offset)
+{
+	uint32_t val;
+
+	memcpy(&val, pos,  sizeof(val));
+	val = cpu_to_fdt32(fdt32_to_cpu(val) + offset);
+	memcpy(pos, &val, sizeof(val));
+}
+
+/*
+ * Process local fixups
+ * @fixups is property value, array of NUL-terminated strings
+ *   with fixup locations
+ * @fixups_len length of the fixups array in bytes
+ * @offset value these locations should be increased by
+ */
+static int
+fdt_do_local_fixup(void *fdtp, const char *fixups, int fixups_len, int offset)
+{
+	void *fixup_pos;
+
+	while (fixups_len > 0) {
+		fixup_pos = fdt_get_fixup_location(fdtp, fixups);
+		if (fixup_pos != NULL)
+			fdt_increase_u32(fixup_pos, offset);
+
+		fixups_len -= strlen(fixups) + 1;
+		fixups += strlen(fixups) + 1;
+	}
+
+	return (0);
+}
+
+/*
+ * Increase node phandle by phandle_offset
+ */
+static void
+fdt_increase_phandle(void *fdtp, int node_offset, uint32_t phandle_offset)
+{
+	int proplen;
+	void *phandle_pos, *node_pos;
+
+	node_pos = (char*)fdtp + node_offset;
+
+	phandle_pos = fdt_getprop_w(fdtp, node_offset, "phandle", &proplen);
+	if (phandle_pos)
+		fdt_increase_u32(phandle_pos, phandle_offset);
+	phandle_pos = fdt_getprop_w(fdtp, node_offset, "linux,phandle", &proplen);
+	if (phandle_pos)
+		fdt_increase_u32(phandle_pos, phandle_offset);
+}
+
+/*
+ * Increase all phandles by offset
+ */
+static void
+fdt_increase_phandles(void *fdtp, uint32_t offset)
+{
+	int o, depth;
+
+	o = fdt_path_offset(fdtp, "/");
+	for (depth = 0; (o >= 0) && (depth >= 0); o = fdt_next_node(fdtp, o, &depth)) {
+		fdt_increase_phandle(fdtp, o, offset);
+	}
+}
+
+/*
+ * Overlay one node defined by <overlay_fdtp, overlay_o> over <main_fdtp, target_o>
+ */
+static void
+fdt_overlay_node(void *main_fdtp, int target_o, void *overlay_fdtp, int overlay_o)
+{
+	int len, o, depth;
+	const char *name;
+	const void *val;
+	int target_subnode_o;
+
+	/* Overlay properties */
+	for (o = fdt_first_property_offset(overlay_fdtp, overlay_o);
+	    o >= 0; o = fdt_next_property_offset(overlay_fdtp, o)) {
+		val = fdt_getprop_by_offset(overlay_fdtp, o, &name, &len);
+		if (val)
+			fdt_setprop(main_fdtp, target_o, name, val, len);
+	}
+
+	/* Now overlay nodes */
+	o = overlay_o;
+        for (depth = 0; (o >= 0) && (depth >= 0);
+	    o = fdt_next_node(overlay_fdtp, o, &depth)) {
+		if (depth != 1)
+			continue;
+		/* Check if there is node with the same name */
+		name = fdt_get_name(overlay_fdtp, o, NULL);
+		target_subnode_o = fdt_subnode_offset(main_fdtp, target_o, name);
+		if (target_subnode_o < 0) {
+			/* create new subnode and run merge recursively */
+			target_subnode_o = fdt_add_subnode(main_fdtp, target_o, name);
+			if (target_subnode_o < 0) {
+				printf("failed to create subnode \"%s\": %d\n",
+				    name, target_subnode_o);
+				return;
+			}
+		}
+
+		fdt_overlay_node(main_fdtp, target_subnode_o,
+		    overlay_fdtp, o);
+	}
+}
+
+/*
+ * Apply one overlay fragment
+ */
+static void
+fdt_apply_fragment(void *main_fdtp, void *overlay_fdtp, int fragment_o)
+{
+	uint32_t target;
+	const char *target_path;
+	const void *val;
+	int target_node_o, overlay_node_o;
+
+	target_node_o = -1;
+	val = fdt_getprop(overlay_fdtp, fragment_o, "target", NULL);
+	if (val) {
+		memcpy(&target, val, sizeof(target));
+		target = fdt32_to_cpu(target);
+		target_node_o = fdt_node_offset_by_phandle(main_fdtp, target);
+		if (target_node_o < 0) {
+			printf("failed to find target %04x\n", target);
+			return;
+		}
+	}
+
+	if (target_node_o < 0) {
+		target_path = fdt_getprop(overlay_fdtp, fragment_o, "target-path", NULL);
+		if (target_path == NULL)
+			return;
+
+		target_node_o = fdt_path_offset(main_fdtp, target_path);
+		if (target_node_o < 0) {
+			printf("failed to find target-path %s\n", target_path);
+			return;
+		}
+	}
+
+	if (target_node_o < 0)
+		return;
+
+	overlay_node_o = fdt_subnode_offset(overlay_fdtp, fragment_o, "__overlay__");
+	if (overlay_node_o < 0) {
+		printf("missing __overlay__ sub-node\n");
+		return;
+	}
+
+	fdt_overlay_node(main_fdtp, target_node_o, overlay_fdtp, overlay_node_o);
+}
+
+/*
+ * Handle __fixups__ node in overlay DTB
+ */
+static int
+fdt_overlay_do_fixups(void *main_fdtp, void *overlay_fdtp)
+{
+	int main_symbols_o, symbol_o, overlay_fixups_o;
+	int fixup_prop_o;
+	int len;
+	const char *fixups, *name;
+	const char *symbol_path;
+	uint32_t phandle;
+
+	main_symbols_o = fdt_path_offset(main_fdtp, "/__symbols__");
+	overlay_fixups_o = fdt_path_offset(overlay_fdtp, "/__fixups__");
+
+	if (main_symbols_o < 0)
+		return (-1);
+	if (overlay_fixups_o < 0)
+		return (-1);
+
+	for (fixup_prop_o = fdt_first_property_offset(overlay_fdtp, overlay_fixups_o);
+	    fixup_prop_o >= 0;
+	    fixup_prop_o = fdt_next_property_offset(overlay_fdtp, fixup_prop_o)) {
+		fixups = fdt_getprop_by_offset(overlay_fdtp, fixup_prop_o, &name, &len);
+		symbol_path = fdt_getprop(main_fdtp, main_symbols_o, name, NULL);
+		if (symbol_path == NULL) {
+			printf("couldn't find \"%s\" symbol in main dtb\n", name);
+			return (-1);
+		}
+		symbol_o = fdt_path_offset(main_fdtp, symbol_path);
+		if (symbol_o < 0) {
+			printf("couldn't find \"%s\" path in main dtb\n", symbol_path);
+			return (-1);
+		}
+		phandle = fdt_get_phandle(main_fdtp, symbol_o);
+		if (fdt_do_one_fixup(overlay_fdtp, fixups, len, phandle) < 0)
+			return (-1);
+	}
+
+	return (0);
+}
+
+/*
+ * Handle __local_fixups__ node in overlay DTB
+ */
+static int
+fdt_overlay_do_local_fixups(void *main_fdtp, void *overlay_fdtp)
+{
+	int overlay_local_fixups_o;
+	int len;
+	const char *fixups;
+	uint32_t phandle_offset;
+
+	overlay_local_fixups_o = fdt_path_offset(overlay_fdtp, "/__local_fixups__");
+
+	if (overlay_local_fixups_o < 0)
+		return (-1);
+
+	phandle_offset = fdt_max_phandle(main_fdtp);
+	fdt_increase_phandles(overlay_fdtp, phandle_offset);
+	fixups = fdt_getprop_w(overlay_fdtp, overlay_local_fixups_o, "fixup", &len);
+	if (fixups) {
+		if (fdt_do_local_fixup(overlay_fdtp, fixups, len, phandle_offset) < 0)
+			return (-1);
+	}
+
+	return (0);
+}
+
+/*
+ * Apply all fragments to main DTB
+ */
+static int
+fdt_overlay_apply_fragments(void *main_fdtp, void *overlay_fdtp)
+{
+	int o, depth;
+
+	o = fdt_path_offset(overlay_fdtp, "/");
+	for (depth = 0; (o >= 0) && (depth >= 0); o = fdt_next_node(overlay_fdtp, o, &depth)) {
+		if (depth != 1)
+			continue;
+
+		fdt_apply_fragment(main_fdtp, overlay_fdtp, o);
+	}
+
+	return (0);
+}
+
+int
+fdt_overlay_apply(void *main_fdtp, void *overlay_fdtp, size_t overlay_length)
+{
+	void *overlay_copy;
+	int rv;
+
+	rv = 0;
+
+	/* We modify overlay in-place, so we need writable copy */
+	overlay_copy = malloc(overlay_length);
+	if (overlay_copy == NULL) {
+		printf("failed to allocate memory for overlay copy\n");
+		return (-1);
+	}
+
+	memcpy(overlay_copy, overlay_fdtp, overlay_length);
+
+	if (fdt_overlay_do_fixups(main_fdtp, overlay_copy) < 0) {
+		printf("failed to perform fixups in overlay\n");
+		rv = -1;
+		goto out;
+	}
+
+	if (fdt_overlay_do_local_fixups(main_fdtp, overlay_copy) < 0) {
+		printf("failed to perform local fixups in overlay\n");
+		rv = -1;
+		goto out;
+	}
+
+	if (fdt_overlay_apply_fragments(main_fdtp, overlay_copy) < 0) {
+		printf("failed to apply fragments\n");
+		rv = -1;
+	}
+
+out:
+	free(overlay_copy);
+
+	return (rv);
+}
diff --git a/sys/boot/fdt/fdt_overlay.h b/sys/boot/fdt/fdt_overlay.h
new file mode 100644
index 0000000000000..0f9134384d3c2
--- /dev/null
+++ b/sys/boot/fdt/fdt_overlay.h
@@ -0,0 +1,34 @@
+/*-
+ * Copyright (c) 2015 Oleksandr Tymoshenko <gonzo@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef FDT_OVERLAY_H
+#define FDT_OVERLAY_H
+
+int fdt_overlay_apply(void *main_fdtp, void *overlay_fdtp, size_t overlay_length);
+
+#endif /* FDT_OVERLAY_H */
diff --git a/sys/boot/fdt/fdt_platform.h b/sys/boot/fdt/fdt_platform.h
index cad760279b24d..eae940aab0303 100644
--- a/sys/boot/fdt/fdt_platform.h
+++ b/sys/boot/fdt/fdt_platform.h
@@ -43,8 +43,10 @@ void fdt_fixup_cpubusfreqs(unsigned long, unsigned long);
 void fdt_fixup_ethernet(const char *, char *, int);
 void fdt_fixup_memory(struct fdt_mem_region *, size_t);
 void fdt_fixup_stdout(const char *);
+void fdt_apply_overlays(void);
 int fdt_load_dtb_addr(struct fdt_header *);
 int fdt_load_dtb_file(const char *);
+int fdt_load_dtb_overlays(const char *);
 int fdt_setup_fdtp(void);
 
 /* The platform library needs to implement these functions */
diff --git a/sys/boot/uboot/fdt/uboot_fdt.c b/sys/boot/uboot/fdt/uboot_fdt.c
index 6b646f63dc815..848d8594222ca 100644
--- a/sys/boot/uboot/fdt/uboot_fdt.c
+++ b/sys/boot/uboot/fdt/uboot_fdt.c
@@ -45,6 +45,7 @@ fdt_platform_load_dtb(void)
 	struct fdt_header *hdr;
 	const char *s;
 	char *p;
+	int rv;
 
 	/*
 	 * If the U-boot environment contains a variable giving the address of a
@@ -68,6 +69,8 @@ fdt_platform_load_dtb(void)
 		}
 	}
 
+	rv = 1;
+
 	/*
 	 * Try to get FDT filename first from loader env and then from u-boot env
 	 */
@@ -79,11 +82,21 @@ fdt_platform_load_dtb(void)
 	if (s != NULL && *s != '\0') {
 		if (fdt_load_dtb_file(s) == 0) {
 			printf("Loaded DTB from file '%s'.\n", s);
-			return (0);
+			rv = 0;
 		}
 	}
 
-	return (1);
+	if (rv == 0) {
+		s = getenv("fdt_overlays");
+		if (s == NULL)
+			s = ub_env_get("fdt_overlays");
+		if (s != NULL && *s != '\0') {
+			printf("Loading DTB overlays: '%s'\n", s);
+			fdt_load_dtb_overlays(s);
+		}
+	}
+
+	return (rv);
 }
 
 void
@@ -99,6 +112,9 @@ fdt_platform_fixups(void)
 	eth_no = 0;
 	ethstr = NULL;
 
+	/* Apply overlays before anything else */
+	fdt_apply_overlays();
+
 	/* Acquire sys_info */
 	si = ub_get_sys_info();