From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Thu, 28 Jul 2016 15:43:25 +0200
Subject: ar71xx: add revision detection for D-Link DIR-505 A1/A2

The A1 image also works on the A2, correctly set AR71XX_MODEL in this case.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>

Backport of LEDE 500a67a167a256002f8ab05171f49dfb86b03260

diff --git a/target/linux/ar71xx/base-files/lib/ar71xx.sh b/target/linux/ar71xx/base-files/lib/ar71xx.sh
index 748b9c7..28066b1 100755
--- a/target/linux/ar71xx/base-files/lib/ar71xx.sh
+++ b/target/linux/ar71xx/base-files/lib/ar71xx.sh
@@ -107,6 +107,15 @@ cybertan_get_hw_magic() {
 	dd bs=8 count=1 skip=0 if=$part 2>/dev/null | hexdump -v -n 8 -e '1/1 "%02x"'
 }
 
+dir505_board_detect() {
+	local dev=$(find_mtd_part 'mac')
+	[ -z "$dev" ] && return
+
+	# The revision is stored at the beginning of the "mac" partition
+	local rev="$(LC_CTYPE=C awk -v 'FS=[^[:print:]]' '{print $1; exit}' $dev)"
+	AR71XX_MODEL="D-Link DIR-505 rev. $rev"
+}
+
 tplink_get_hwid() {
 	local part
 
@@ -453,6 +462,7 @@ ar71xx_board_detect() {
 		;;
 	*"DIR-505 rev. A1")
 		name="dir-505-a1"
+		dir505_board_detect
 		;;
 	*"DIR-600 rev. A1")
 		name="dir-600-a1"