build: add a script for generating Linksys factory images

This commit adds the 'Build/linksys-image' rule and the
'linksys-image.sh' script to the build system.

This change is needed for generating factory images for the Linksys
EA6350v3 device. Without this patch, only valid sysupgrade images can be
generated. With this patch, users can flash the device without the
need of physical access or disassembly.

Signed-off-by: Ryan Pannell <ryan@osukl.com>
Signed-off-by: Oever González <notengobattery@gmail.com>

include/image-commands.mk

@@ -274,6 +274,13 @@ define Build/combined-image
 	@mv $@.new $@
 endef
 
+define Build/linksys-image
+	$(TOPDIR)/scripts/linksys-image.sh \
+		"$(call param_get_default,type,$(1),$(DEVICE_NAME))" \
+		$@ $@.new
+		mv $@.new $@
+endef
+
 define Build/openmesh-image
 	$(TOPDIR)/scripts/om-fwupgradecfg-gen.sh \
 		"$(call param_get_default,ce_type,$(1),$(DEVICE_NAME))" \

scripts/linksys-image.sh

@@ -0,0 +1,67 @@
+#!/bin/sh
+#
+# Copyright (C) 2018 Oceanic Systems (UK) Ltd
+#
+# This is free software, licensed under the GNU General Public License v2.
+# See /LICENSE for more information.
+#
+# Maintained by: Ryan Pannell <ryan [at] o s u k l .com> <github.com/Escalion>
+#
+# Write Linksys signature for factory image
+# This is appended to the factory image and is tested by the Linksys Upgrader - as observed in civic.
+# The footer is 256 bytes. The format is:
+#  .LINKSYS.        This is detected by the Linksys upgrader before continuing with upgrade. (9 bytes)
+#  <VERSION>        The version number of upgrade. Not checked so use arbitary value (8 bytes)
+#  <TYPE>           Model of target device, padded (0x20) to (15 bytes)
+#  <CRC>      	    CRC checksum of the image to flash (8 byte)
+#  <padding>	    Padding (0x20) (7 bytes)
+#  <signature>	    Signature of signer. Not checked so use Arbitary value (16 bytes)
+#  <padding>        Padding (0x00) (192 bytes)
+#  0x0A		    (1 byte)
+
+## version history
+# * version 1: initial commit
+
+set -e
+
+ME="${0##*/}"
+
+usage() {
+	echo "Usage: $ME <type> <in filename>"
+	[ "$IMG_OUT" ] && rm -f "$IMG_OUT"
+	exit 1
+}
+
+[ "$#" -lt 3 ] && usage
+
+TYPE=$1
+
+tmpdir="$( mktemp -d 2> /dev/null )"
+if [ -z "$tmpdir" ]; then
+	# try OSX signature
+	tmpdir="$( mktemp -t 'ubitmp' -d )"
+fi
+
+if [ -z "$tmpdir" ]; then
+	exit 1
+fi
+
+trap "rm -rf $tmpdir" EXIT
+
+IMG_TMP_OUT="${tmpdir}/out"
+
+IMG_IN=$2
+IMG_OUT="${IMG_IN}.new"
+
+[ ! -f "$IMG_IN" ] && echo "$ME: Not a valid image: $IMG_IN" && usage
+
+dd if="${IMG_IN}" of="${IMG_TMP_OUT}"
+CRC=$(printf "%08X" $(dd if="${IMG_IN}" bs=$(stat -c%s "${IMG_IN}") count=1|cksum| cut -d ' ' -f1))
+
+printf ".LINKSYS.01000409%-15s%-8s%-7s%-16s" "${TYPE}" "${CRC}" "" "K0000000F0246434" >> "${IMG_TMP_OUT}"
+
+dd if=/dev/zero bs=1 count=192 conv=notrunc >> "${IMG_TMP_OUT}"
+
+printf '\12' >> "${IMG_TMP_OUT}"
+
+cp "${IMG_TMP_OUT}" "${IMG_OUT}"