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Subject[PATCH v2] dtc: create tool to diff device trees
From: Frank Rowand <frank.rowand@sonymobile.com>

Create script to diff device trees.

The device tree can be in any of the forms recognized by the dtc compiler:
- source
- binary blob
- file system tree (from /proc/devicetree)

If the device tree is a source file, then it is pre-processed in the
same way as it would be when built in the linux kernel source tree
before diffing.

Signed-off-by: Frank Rowand <frank.rowand@sonymobile.com>
---

Tools to develop and debug device tree are somewhat inadequate. This is a
small step in improving the situation.

Rationale for and examples of using the script are provided in slides
1 - 78 of the elce 2015 presentation "Solving Device Tree Issues",
which can be found at:

http://elinux.org/images/0/04/Dt_debugging_elce_2015_151006_0421.pdf

(The script was named dtdiff instead of dtx_diff in the presentation.)

Changes in v2:
- Remove dt-bindings from list of includes in cpp_flags
- Remove arch_dtc_flags, which were generated from the arch specific
dts makefile
- Reformat to 8 character tabs
- compile_to_dts(): added back missing return for binary blob


scripts/dtc/dtx_diff | 343 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 343 insertions(+)

Index: b/scripts/dtc/dtx_diff
===================================================================
--- /dev/null
+++ b/scripts/dtc/dtx_diff
@@ -0,0 +1,343 @@
+#! /bin/bash
+
+# Copyright (C) 2015 Frank Rowand
+#
+# This program 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; version 2 of the License.
+
+
+usage() {
+
+ # use spaces instead of tabs in the usage message
+ cat >&2 <<eod
+
+Usage:
+
+ `basename $0` DTx
+ decompile DTx
+
+ `basename $0` DTx_1 DTx_2
+ diff DTx_1 and DTx_2
+
+
+ -f print full dts in diff (--unified=99999)
+ -h synonym for --help
+ -help synonym for --help
+ --help print this message and exit
+ -s SRCTREE linux kernel source tree is at path SRCTREE
+ (default is current directory)
+ -S linux kernel source tree is at root of current git repo
+ -u unsorted, do not sort DTx
+
+
+Each DTx is processed by the dtc compiler to produce a sorted dts source
+file. If DTx is a dts source file then it is pre-processed in the same
+manner as done for the compile of the dts source file in the Linux kernel
+build system ('#include' and '/include/' directives are processed).
+
+If two DTx are provided, the resulting dts source files are diffed.
+
+If DTx is a directory, it is treated as a DT subtree, such as
+ /proc/device-tree.
+
+If DTx contains the binary blob magic value in the first four bytes,
+ it is treated as a binary blob (aka .dtb or FDT).
+
+Otherwise DTx is treated as a dts source file (aka .dts).
+
+ If this script is not run from the root of the linux source tree,
+ and DTx utilizes '#include' or '/include/' then the path of the
+ linux source tree can be provided by '-s SRCTREE' or '-S' so that
+ include paths will be set properly.
+
+ The shell variable \${ARCH} must provide the architecture containing
+ the dts source file for include paths to be set properly for '#include'
+ or '/include/' to be processed.
+
+ If DTx_1 and DTx_2 are in different architectures, then this script
+ may not work since \${ARCH} is part of the include path. Two possible
+ workarounds:
+
+ `basename $0` \\
+ <(ARCH=arch_of_dtx_1 `basename $0` DTx_1) \\
+ <(ARCH=arch_of_dtx_2 `basename $0` DTx_2)
+
+ `basename $0` ARCH=arch_of_dtx_1 DTx_1 >tmp_dtx_1.dts
+ `basename $0` ARCH=arch_of_dtx_2 DTx_2 >tmp_dtx_2.dts
+ `basename $0` tmp_dtx_1.dts tmp_dtx_2.dts
+ rm tmp_dtx_1.dts tmp_dtx_2.dts
+
+ If DTx_1 and DTx_2 are in different directories, then this script will
+ add the path of DTx_1 and DTx_2 to the include paths. If DTx_2 includes
+ a local file that exists in both the path of DTx_1 and DTx_2 then the
+ file in the path of DTx_1 will incorrectly be included. Possible
+ workaround:
+
+ `basename $0` DTx_1 >tmp_dtx_1.dts
+ `basename $0` DTx_2 >tmp_dtx_2.dts
+ `basename $0` tmp_dtx_1.dts tmp_dtx_2.dts
+ rm tmp_dtx_1.dts tmp_dtx_2.dts
+
+eod
+}
+
+
+compile_to_dts() {
+
+ dtx="$1"
+
+ if [ -d "${dtx}" ] ; then
+
+ # ----- input is file tree
+
+ if ( ! ${DTC} -I fs ${dtx} ) ; then
+ exit 3
+ fi
+
+ elif [ -f "${dtx}" ] && [ -r "${dtx}" ] ; then
+
+ magic=`hexdump -n 4 -e '/1 "%02x"' ${dtx}`
+ if [ "${magic}" = "d00dfeed" ] ; then
+
+ # ----- input is FDT (binary blob)
+
+ if ( ! ${DTC} -I dtb ${dtx} ) ; then
+ exit 3
+ fi
+
+ return
+
+ fi
+
+ # ----- input is DTS (source)
+
+ if ( cpp ${cpp_flags} -x assembler-with-cpp ${dtx} \
+ | ${DTC} -I dts ) ; then
+ return
+ fi
+
+ echo "" >&2
+ echo "Possible hints to resolve the above error:" >&2
+ echo " (hints might not fix the problem)" >&2
+
+ hint_given=0
+
+ if [ "${ARCH}" = "" ] ; then
+ hint_given=1
+ echo "" >&2
+ echo " shell variable \$ARCH not set" >&2
+ fi
+
+ dtx_arch=`echo "/${dtx}" | sed -e 's|.*/arch/||' -e 's|/.*||'`
+
+ if [ "${dtx_arch}" != "" -a "${dtx_arch}" != "${ARCH}" ] ; then
+ hint_given=1
+ echo "" >&2
+ echo " architecture ${dtx_arch} is in file path," >&2
+ echo " but does not match shell variable \$ARCH" >&2
+ echo " (${ARCH}) does not match shell variable" >&2
+ echo " \$ARCH (${ARCH})" >&2
+ fi
+
+ if [ ! -d ${srctree}/arch/${ARCH} ] ; then
+ hint_given=1
+ echo "" >&2
+ echo " ${srctree}/arch/${ARCH}/ does not exist" >&2
+ echo " Is \$ARCH='${ARCH}' correct?" >&2
+ echo " Possible fix: use '-s' option" >&2
+
+ git_root=`git rev-parse --show-toplevel 2>/dev/null`
+ if [ -d ${git_root}/arch/ ] ; then
+ echo " Possible fix: use '-S' option" >&2
+ fi
+ fi
+
+ if [ $hint_given = 0 ] ; then
+ echo "" >&2
+ echo " No hints available." >&2
+ fi
+
+ echo "" >&2
+
+ exit 3
+
+ else
+ echo "" >&2
+ echo "ERROR: ${dtx} does not exist or is not readable" >&2
+ echo "" >&2
+ exit 2
+ fi
+
+}
+
+
+# ----- start of script
+
+cmd_diff=0
+diff_flags="-u"
+dtx_file_1=""
+dtx_file_2=""
+dtc_sort="-s"
+help=0
+srctree=""
+
+
+while [ $# -gt 0 ] ; do
+
+ case $1 in
+
+ -f )
+ diff_flags="--unified=999999"
+ shift
+ ;;
+
+ -h | -help | --help )
+ help=1
+ shift
+ ;;
+
+ -s )
+ srctree="$2"
+ shift 2
+ ;;
+
+ -S )
+ git_root=`git rev-parse --show-toplevel 2>/dev/null`
+ srctree="${git_root}"
+ shift
+ ;;
+
+ -u )
+ dtc_sort=""
+ shift
+ ;;
+
+ *)
+ if [ "${dtx_file_1}" = "" ] ; then
+ dtx_file_1="$1"
+ elif [ "${dtx_file_2}" = "" ] ; then
+ dtx_file_2="$1"
+ else
+ echo "" >&2
+ echo "ERROR: Unexpected parameter: $1" >&2
+ echo "" >&2
+ exit 2
+ fi
+ shift
+ ;;
+
+ esac
+
+done
+
+if [ "${srctree}" = "" ] ; then
+ srctree="."
+fi
+
+if [ "${dtx_file_2}" != "" ]; then
+ cmd_diff=1
+fi
+
+if (( ${help} )) ; then
+ usage
+ exit 1
+fi
+
+# this must follow check for ${help}
+if [ "${dtx_file_1}" = "" ]; then
+ echo "" >&2
+ echo "ERROR: parameter DTx required" >&2
+ echo "" >&2
+ exit 2
+fi
+
+
+# ----- prefer dtc from linux kernel, allow fallback to dtc in $PATH
+
+if [ "${KBUILD_OUTPUT:0:2}" = ".." ] ; then
+ __KBUILD_OUTPUT="${srctree}/${KBUILD_OUTPUT}"
+elif [ "${KBUILD_OUTPUT}" = "" ] ; then
+ __KBUILD_OUTPUT="."
+else
+ __KBUILD_OUTPUT="${KBUILD_OUTPUT}"
+fi
+
+DTC="${__KBUILD_OUTPUT}/scripts/dtc/dtc"
+
+if [ ! -x ${DTC} ] ; then
+ __DTC="dtc"
+ if ( ! which ${__DTC} >/dev/null ) ; then
+
+ # use spaces instead of tabs in the error message
+ cat >&2 <<eod
+
+ERROR: unable to find a 'dtc' program
+
+ Preferred 'dtc' (built from Linux kernel source tree) was not found or
+ is not executable.
+
+ 'dtc' is: ${DTC}
+
+ If it does not exist, create it from the root of the Linux source tree:
+
+ 'make scripts'.
+
+ If not at the root of the Linux kernel source tree -s SRCTREE or -S
+ may need to be specified to find 'dtc'.
+
+ If 'O=\${dir}' is specified in your Linux builds, this script requires
+ 'export KBUILD_OUTPUT=\${dir}' or add \${dir}/scripts/dtc to \$PATH
+ before running.
+
+ If \${KBUILD_OUTPUT} is a relative path, then '-s SRCDIR', -S, or run
+ this script from the root of the Linux kernel source tree is required.
+
+ Fallback '${__DTC}' was also not in \${PATH} or is not executable.
+
+eod
+ exit 2
+ fi
+ DTC=${__DTC}
+fi
+
+
+# ----- cpp and dtc flags same as for linux source tree build of .dtb files,
+# plus directories of the dtx file(s)
+
+dtx_path_1_dtc_include="-i `dirname ${dtx_file_1}`"
+
+dtx_path_2_dtc_include=""
+if (( ${cmd_diff} )) ; then
+ dtx_path_2_dtc_include="-i `dirname ${dtx_file_2}`"
+fi
+
+cpp_flags="\
+ -nostdinc \
+ -I${srctree}/arch/${ARCH}/boot/dts \
+ -I${srctree}/arch/${ARCH}/boot/dts/include \
+ -I${srctree}/drivers/of/testcase-data \
+ -undef -D__DTS__"
+
+dtc_flags="\
+ -i ${srctree}/arch/${ARCH}/boot/dts/ \
+ -i ${srctree}/kernel/dts \
+ ${dtx_path_1_dtc_include} \
+ ${dtx_path_2_dtc_include}"
+
+DTC="${DTC} ${dtc_flags} -O dts -qq -f ${dtc_sort} -o -"
+
+
+# ----- do the diff or decompile
+
+if (( ${cmd_diff} )) ; then
+
+ diff ${diff_flags} \
+ <(compile_to_dts "${dtx_file_1}") \
+ <(compile_to_dts "${dtx_file_2}")
+
+else
+
+ compile_to_dts "${dtx_file_1}"
+
+fi
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