make_dev_firmware: provide more usage help for backup files

scripts/image_signing/make_dev_firmware.sh

 #!/bin/sh
 #
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # This script can change key (usually developer keys) in a firmware binary
 # image or system live firmware (EEPROM), and assign proper HWID, BMPFV as well.
 
 SCRIPT_BASE="$(dirname "$0")"
@@ skipping 182 matching lines @@
   # TODO(hungte) compare if the image really needs to be changed.
 
   debug_msg "Check if we need to make backup file(s)"
   if [ -n "$backup_image" ]; then
     local backup_hwid_name="$(echo "$old_hwid" | sed 's/ /_/g')"
     local backup_date_time="$(date +'%Y%m%d_%H%M%S')"
     local backup_file_name="firmware_${backup_hwid_name}_${backup_date_time}.fd"
     local backup_file_path="$FLAGS_backup_dir/$backup_file_name"
     if mkdir -p "$FLAGS_backup_dir" &&
        cp -f "$backup_image" "$backup_file_path"; then
-      echo "Backup of current firmware image is stored in: $backup_file_path"
+      true
+    elif cp -f "$backup_image" "/tmp/$backup_file_name"; then
+      backup_file_path="/tmp/$backup_file_name"
+    else
+      backup_file_path=''
+    fi
+    if [ -n "$backup_file_path" -a -s "$backup_file_path" ]; then
+      # TODO(hungte) maybe we can wrap the flashrom by 'make_dev_firmware.sh -r'
+      # so that the only command to remember would be make_dev_firmware.sh.

[Randall Spangler, 2010/10/18 15:34:32]

Good idea.

+      echo "
+      Backup of current firmware image is stored in:
+        $backup_file_path
+      Please copy the backup file to a safe place ASAP.
+
+      To stop using devkeys and restore original firmware, execute command:
+        flashrom -w [PATH_TO_BACKUP_IMAGE]
+      Ex: flashrom -w $backup_file_path
+      "
     else
       echo "WARNING: Cannot create file in $FLAGS_backup_dir... Ignore backups."
     fi
   fi
 
   # TODO(hungte) use vbutil_firmware to check if the new firmware is valid.
   # Or, do verification in resign_firmwarefd.sh and trust it.
 
   debug_msg "Write the image"
   write_image ||
     err_die "Failed to write image. Error message: $(cat "$EXEC_LOG")"
 
   debug_msg "Complete."
   if [ -z "$FLAGS_to" ]; then
     echo "Successfully changed firmware to Developer Keys. New HWID: $new_hwid"
   else
     echo "Firmware '$FLAGS_to' now uses Developer Keys. New HWID: $new_hwid"
   fi
 }
 
 main