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 #! /bin/sh
 # SPDX-License-Identifier: GPL-2.0
 # Copyright (c) 2020, Google LLC. All rights reserved.
 # Author: Saravana Kannan <saravanak@google.com>
 
 function help() {
         cat << EOF
 Usage: $(basename $0) [-c|-d|-m|-f] [filter options] <list of devices>
 
 This script needs to be run on the target device once it has booted to a
 shell.
 
 The script takes as input a list of one or more device directories under
 /sys/devices and then lists the probe dependency chain (suppliers and
 parents) of these devices. It does a breadth first search of the dependency
 chain, so the last entry in the output is close to the root of the
 dependency chain.
 
 By default it lists the full path to the devices under /sys/devices.
 
 It also takes an optional modifier flag as the first parameter to change
 what information is listed in the output. If the requested information is
 not available, the device name is printed.
 
   -c    lists the compatible string of the dependencies
   -d    lists the driver name of the dependencies that have probed
   -m    lists the module name of the dependencies that have a module
   -f    list the firmware node path of the dependencies
   -g    list the dependencies as edges and nodes for graphviz
   -t    list the dependencies as edges for tsort
 
 The filter options provide a way to filter out some dependencies:
   --allow-no-driver     By default dependencies that don't have a driver
                         attached are ignored. This is to avoid following
                         device links to "class" devices that are created
                         when the consumer probes (as in, not a probe
                         dependency). If you want to follow these links
                         anyway, use this flag.
 
   --exclude-devlinks    Don't follow device links when tracking probe
                         dependencies.
 
   --exclude-parents     Don't follow parent devices when tracking probe
                         dependencies.
 
 EOF
 }
 
 function dev_to_detail() {
         local i=0
         while [ $i -lt ${#OUT_LIST[@]} ]
         do
                 local C=${OUT_LIST[i]}
                 local S=${OUT_LIST[i+1]}
                 local D="'$(detail_chosen $C $S)'"
                 if [ ! -z "$D" ]
                 then
                         # This weirdness is needed to work with toybox when
                         # using the -t option.
                         printf '%05u\t%s\n' ${i} "$D" | tr -d \'
                 fi
                 i=$((i+2))
         done
 }
 
 function already_seen() {
         local i=0
         while [ $i -lt ${#OUT_LIST[@]} ]
         do
                 if [ "$1" = "${OUT_LIST[$i]}" ]
                 then
                         # if-statement treats 0 (no-error) as true
                         return 0
                 fi
                 i=$(($i+2))
         done
 
         # if-statement treats 1 (error) as false
         return 1
 }
 
 # Return 0 (no-error/true) if parent was added
 function add_parent() {
 
         if [ ${ALLOW_PARENTS} -eq 0 ]
         then
                 return 1
         fi
 
         local CON=$1
         # $CON could be a symlink path. So, we need to find the real path and
         # then go up one level to find the real parent.
         local PARENT=$(realpath $CON/..)
 
         while [ ! -e ${PARENT}/driver ]
         do
                 if [ "$PARENT" = "/sys/devices" ]
                 then
                         return 1
                 fi
                 PARENT=$(realpath $PARENT/..)
         done
 
         CONSUMERS+=($PARENT)
         OUT_LIST+=(${CON} ${PARENT})
         return 0
 }
 
 # Return 0 (no-error/true) if one or more suppliers were added
 function add_suppliers() {
         local CON=$1
         local RET=1
 
         if [ ${ALLOW_DEVLINKS} -eq 0 ]
         then
                 return 1
         fi
 
         SUPPLIER_LINKS=$(ls -1d $CON/supplier:* 2>/dev/null)
         for SL in $SUPPLIER_LINKS;
         do
                 SYNC_STATE=$(cat $SL/sync_state_only)
 
                 # sync_state_only links are proxy dependencies.
                 # They can also have cycles. So, don't follow them.
                 if [ "$SYNC_STATE" != '0' ]
                 then
                         continue
                 fi
 
                 SUPPLIER=$(realpath $SL/supplier)
 
                 if [ ! -e $SUPPLIER/driver -a ${ALLOW_NO_DRIVER} -eq 0 ]
                 then
                         continue
                 fi
 
                 CONSUMERS+=($SUPPLIER)
                 OUT_LIST+=(${CON} ${SUPPLIER})
                 RET=0
         done
 
         return $RET
 }
 
 function detail_compat() {
         f=$1/of_node/compatible
         if [ -e $f ]
         then
                 echo -n $(cat $f)
         else
                 echo -n $1
         fi
 }
 
 function detail_module() {
         f=$1/driver/module
         if [ -e $f ]
         then
                 echo -n $(basename $(realpath $f))
         else
                 echo -n $1
         fi
 }
 
 function detail_driver() {
         f=$1/driver
         if [ -e $f ]
         then
                 echo -n $(basename $(realpath $f))
         else
                 echo -n $1
         fi
 }
 
 function detail_fwnode() {
         f=$1/firmware_node
         if [ ! -e $f ]
         then
                 f=$1/of_node
         fi
 
         if [ -e $f ]
         then
                 echo -n $(realpath $f)
         else
                 echo -n $1
         fi
 }
 
 function detail_graphviz() {
         if [ "$2" != "ROOT" ]
         then
                 echo -n "\"$(basename $2)\"->\"$(basename $1)\""
         else
                 echo -n "\"$(basename $1)\""
         fi
 }
 
 function detail_tsort() {
         echo -n "\"$2\" \"$1\""
 }
 
 function detail_device() { echo -n $1; }
 
 alias detail=detail_device
 ALLOW_NO_DRIVER=0
 ALLOW_DEVLINKS=1
 ALLOW_PARENTS=1
 
 while [ $# -gt 0 ]
 do
         ARG=$1
         case $ARG in
                 --help)
                         help
                         exit 0
                         ;;
                 -c)
                         alias detail=detail_compat
                         ;;
                 -m)
                         alias detail=detail_module
                         ;;
                 -d)
                         alias detail=detail_driver
                         ;;
                 -f)
                         alias detail=detail_fwnode
                         ;;
                 -g)
                         alias detail=detail_graphviz
                         ;;
                 -t)
                         alias detail=detail_tsort
                         ;;
                 --allow-no-driver)
                         ALLOW_NO_DRIVER=1
                         ;;
                 --exclude-devlinks)
                         ALLOW_DEVLINKS=0
                         ;;
                 --exclude-parents)
                         ALLOW_PARENTS=0
                         ;;
                 *)
                         # Stop at the first argument that's not an option.
                         break
                         ;;
         esac
         shift
 done
 
 function detail_chosen() {
         detail $1 $2
 }
 
 if [ $# -eq 0 ]
 then
         help
         exit 1
 fi
 
 CONSUMERS=($@)
 OUT_LIST=()
 
 # Do a breadth first, non-recursive tracking of suppliers. The parent is also
 # considered a "supplier" as a device can't probe without its parent.
 i=0
 while [ $i -lt ${#CONSUMERS[@]} ]
 do
         CONSUMER=$(realpath ${CONSUMERS[$i]})
         i=$(($i+1))
 
         if already_seen ${CONSUMER}
         then
                 continue
         fi
 
         # If this is not a device with a driver, we don't care about its
         # suppliers.
         if [ ! -e ${CONSUMER}/driver -a ${ALLOW_NO_DRIVER} -eq 0 ]
         then
                 continue
         fi
 
         ROOT=1
 
         # Add suppliers to CONSUMERS list and output the consumer details.
         #
         # We don't need to worry about a cycle in the dependency chain causing
         # infinite loops. That's because the kernel doesn't allow cycles in
         # device links unless it's a sync_state_only device link. And we ignore
         # sync_state_only device links inside add_suppliers.
         if add_suppliers ${CONSUMER}
         then
                 ROOT=0
         fi
 
         if add_parent ${CONSUMER}
         then
                 ROOT=0
         fi
 
         if [ $ROOT -eq 1 ]
         then
                 OUT_LIST+=(${CONSUMER} "ROOT")
         fi
 done
 
 # Can NOT combine sort and uniq using sort -suk2 because stable sort in toybox
 # isn't really stable.
 dev_to_detail | sort -k2 -k1 | uniq -f 1 | sort | cut -f2-
 
 exit 0

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