[PATCH] dtc: create tool to diff device trees

[Frank Rowand]

From: Frank Rowand <frank.rowand@xxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxx>
---

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.)


 scripts/dtc/dtx_diff |  368 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 368 insertions(+)

Index: b/scripts/dtc/dtx_diff
===================================================================
--- /dev/null
+++ b/scripts/dtc/dtx_diff
@@ -0,0 +1,368 @@
+#! /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
+
+		else
+
+			# -----  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 ${dtx_arch} is in file path, but"       >&2
+				echo "  does not match shell variable \$ARCH (${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
+
+		fi
+	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}/arch/${ARCH}/boot/dts/include/dt-bindings \
+	-I${srctree}/drivers/of/testcase-data                  \
+	-undef -D__DTS__"
+
+_dts_makefile=""
+
+if [ -f ${srctree}/arch/${ARCH}/boot/dts/Makefile ] ; then
+	_dts_makefile="${srctree}/arch/${ARCH}/boot/dts/Makefile"
+elif [ -f ${srctree}/arch/${ARCH}/boot/Makefile ] ; then
+	# arch/powerpc
+	_dts_makefile="${srctree}/arch/${ARCH}/boot/Makefile"
+fi
+
+if [ "${_dts_makefile}" != "" ] ; then
+	arch_dtc_flags=`grep DTC_FLAGS ${_dts_makefile} \
+		| grep -v "^#"                              \
+		| sed -e 's|.*=||' `
+else
+	arch_dtc_flags=""
+fi
+
+dtc_flags="\
+	-i ${srctree}/arch/${ARCH}/boot/dts/ \
+	-i ${srctree}/kernel/dts             \
+	${dtx_path_1_dtc_include}            \
+	${dtx_path_2_dtc_include}            \
+	${arch_dtc_flags}"
+
+DTC="${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
+
+
+# ==============================================================================
+# ______________________________________________________________________________
+# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+# ______________________________________________________________________________
+#  vi config follows:
+#
+#  add "set modelines" to ~/.exrc or ~/.vimrc to set tabs automatically
+#  ex:set tabstop=4 shiftwidth=4 sts=4:
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