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
From git://git.jdl.com/software/dtc.git patch hash be6026838 with
adaptations to include/libfdt.h and lib/libfdt/Makefile for the U-Boot environment.
Signed-off-by: Gerald Van Baren vanbaren@cideas.com ---
This comes from the upstream libfdt (dtc) git repository, added to stay in sync.
include/libfdt.h | 1 + lib/libfdt/Makefile | 2 +- lib/libfdt/fdt_empty_tree.c | 84 +++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 86 insertions(+), 1 deletion(-) create mode 100644 lib/libfdt/fdt_empty_tree.c
diff --git a/include/libfdt.h b/include/libfdt.h index 4589c5f..c93ae28 100644 --- a/include/libfdt.h +++ b/include/libfdt.h @@ -1014,6 +1014,7 @@ int fdt_finish(void *fdt); /* 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/lib/libfdt/Makefile b/lib/libfdt/Makefile index c965577..0693d4b 100644 --- a/lib/libfdt/Makefile +++ b/lib/libfdt/Makefile @@ -27,7 +27,7 @@ LIB = $(obj)libfdt.o
SOBJS =
-COBJS-libfdt += fdt.o fdt_ro.o fdt_rw.o fdt_strerror.o fdt_sw.o fdt_wip.o +COBJS-libfdt += fdt.o fdt_ro.o fdt_rw.o fdt_strerror.o fdt_sw.o fdt_wip.o fdt_empty_tree.o
COBJS-$(CONFIG_OF_LIBFDT) += $(COBJS-libfdt) COBJS-$(CONFIG_FIT) += $(COBJS-libfdt) diff --git a/lib/libfdt/fdt_empty_tree.c b/lib/libfdt/fdt_empty_tree.c new file mode 100644 index 0000000..f72d13b --- /dev/null +++ b/lib/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); +} + -- 1.7.9.5