#! /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"
  	dtc_include="$2"
  
  	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} ${dtc_include} -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 ${dtx_arch} is in file path,"   >&2
  			echo "  but does not match shell variable \$ARCH"    >&2
  			echo "  >>\$ARCH<< is: >>${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 grep -q "^CONFIG_DTC=y" ${__KBUILD_OUTPUT}/.config 2>/dev/null; then
  		make_command='
           make scripts'
  	else
  		make_command='
           Enable CONFIG_DTC in the kernel configuration
           make scripts'
  	fi
  	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_command}
  
        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}/scripts/dtc/include-prefixes  \
  	-undef -D__DTS__"
  
  DTC="\
  	${DTC}                                     \
  	-i ${srctree}/scripts/dtc/include-prefixes \
  	-O dts -qq -f ${dtc_sort} -o -"
  
  
  # -----  do the diff or decompile
  
  if (( ${cmd_diff} )) ; then
  
  	diff ${diff_flags} --label "${dtx_file_1}" --label "${dtx_file_2}" \
  		<(compile_to_dts "${dtx_file_1}" "${dtx_path_1_dtc_include}") \
  		<(compile_to_dts "${dtx_file_2}" "${dtx_path_2_dtc_include}")
  
  else
  
  	compile_to_dts "${dtx_file_1}" "${dtx_path_1_dtc_include}"
  
  fi