libfdt: Add helper function to create a trivial, empty tree
The libfdt read/write functions are now usable enough that it's become a
moderately common pattern to use them to build and manipulate a device
tree from scratch. For example, we do so ourself in our rw_tree1 testcase,
and qemu is starting to use this model when building device trees for some
targets such as e500.
However, the read/write functions require some sort of valid tree to begin
with, so this necessitates either having a trivial canned dtb to begin with
or, more commonly, creating an empty tree using the serial-write functions
first.
This patch adds a helper function which uses the serial-write functions to
create a trivial, empty but complete and valid tree in a supplied buffer,
ready for manipulation with the read/write functions.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
diff --git a/libfdt/Makefile.libfdt b/libfdt/Makefile.libfdt
index d55a6f8..4366627 100644
--- a/libfdt/Makefile.libfdt
+++ b/libfdt/Makefile.libfdt
@@ -6,5 +6,5 @@
LIBFDT_soname = libfdt.$(SHAREDLIB_EXT).1
LIBFDT_INCLUDES = fdt.h libfdt.h
LIBFDT_VERSION = version.lds
-LIBFDT_SRCS = fdt.c fdt_ro.c fdt_wip.c fdt_sw.c fdt_rw.c fdt_strerror.c
+LIBFDT_SRCS = fdt.c fdt_ro.c fdt_wip.c fdt_sw.c fdt_rw.c fdt_strerror.c fdt_empty_tree.c
LIBFDT_OBJS = $(LIBFDT_SRCS:%.c=%.o)
diff --git a/libfdt/fdt_empty_tree.c b/libfdt/fdt_empty_tree.c
new file mode 100644
index 0000000..f72d13b
--- /dev/null
+++ b/libfdt/fdt_empty_tree.c
@@ -0,0 +1,84 @@
+/*
+ * libfdt - Flat Device Tree manipulation
+ * Copyright (C) 2012 David Gibson, IBM Corporation.
+ *
+ * libfdt is dual licensed: you can use it either under the terms of
+ * the GPL, or the BSD license, at your option.
+ *
+ * a) This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this library; if not, write to the Free
+ * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
+ * MA 02110-1301 USA
+ *
+ * Alternatively,
+ *
+ * b) 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 COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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 "libfdt_env.h"
+
+#include <fdt.h>
+#include <libfdt.h>
+
+#include "libfdt_internal.h"
+
+int fdt_create_empty_tree(void *buf, int bufsize)
+{
+ int err;
+
+ err = fdt_create(buf, bufsize);
+ if (err)
+ return err;
+
+ err = fdt_finish_reservemap(buf);
+ if (err)
+ return err;
+
+ err = fdt_begin_node(buf, "");
+ if (err)
+ return err;
+
+ err = fdt_end_node(buf);
+ if (err)
+ return err;
+
+ err = fdt_finish(buf);
+ if (err)
+ return err;
+
+ return fdt_open_into(buf, buf, bufsize);
+}
+
diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
index 35d78b8..73f4975 100644
--- a/libfdt/libfdt.h
+++ b/libfdt/libfdt.h
@@ -1014,6 +1014,7 @@
/* Read-write functions */
/**********************************************************************/
+int fdt_create_empty_tree(void *buf, int bufsize);
int fdt_open_into(const void *fdt, void *buf, int bufsize);
int fdt_pack(void *fdt);
diff --git a/tests/rw_tree1.c b/tests/rw_tree1.c
index f4965ec..103a24d 100644
--- a/tests/rw_tree1.c
+++ b/tests/rw_tree1.c
@@ -57,17 +57,7 @@
fdt = xmalloc(SPACE);
/* First create empty tree with SW */
- CHECK(fdt_create(fdt, SPACE));
-
- CHECK(fdt_finish_reservemap(fdt));
- CHECK(fdt_begin_node(fdt, ""));
- CHECK(fdt_end_node(fdt));
- CHECK(fdt_finish(fdt));
-
- verbose_printf("Built empty tree, totalsize = %d\n",
- fdt_totalsize(fdt));
-
- CHECK(fdt_open_into(fdt, fdt, SPACE));
+ CHECK(fdt_create_empty_tree(fdt, SPACE));
CHECK(fdt_add_mem_rsv(fdt, TEST_ADDR_1, TEST_SIZE_1));
CHECK(fdt_add_mem_rsv(fdt, TEST_ADDR_2, TEST_SIZE_2));
