ath79: add ath9k calibration data MAC addresses patching

This patch copies over the MAC patching helper functions from lantiq's
target/linux/lantiq/base-files/etc/hotplug.d/firmware/12-ath9k-eeprom
file.

Not all vendors bothered to write the correct MAC addresses for the
ath9k wifi into the calibration data. And while ath9k does have some
special dt-properties to extract the addresses from a fixed position,
there are still devices that require userspace to edit or modify
the caldata.

In my case, the MAC address for the Wi-Fi device is stored in an
unsorted key-value based "nvram" database and there's an existing
userspace tool to extract the data.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

target/linux/ath79/base-files/etc/hotplug.d/firmware/10-ath9k-eeprom

@@ -42,6 +42,56 @@ ath9k_eeprom_extract_reverse() {
 	printf "%b" "$caldata" > /lib/firmware/$FIRMWARE
 }
 
+xor() {
+	local val
+	local ret="0x$1"
+	local retlen=${#1}
+
+	shift
+	while [ -n "$1" ]; do
+		val="0x$1"
+		ret=$((ret ^ val))
+		shift
+	done
+
+	printf "%0${retlen}x" "$ret"
+}
+
+ath9k_patch_fw_mac() {
+	local mac=$1
+	local mac_offset=$2
+	local chksum_offset=$3
+	local xor_mac
+	local xor_fw_mac
+	local xor_fw_chksum
+
+	[ -z "$mac" -o -z "$mac_offset" ] && return
+
+	[ -n "$chksum_offset" ] && {
+		xor_mac=${mac//:/}
+		xor_mac="${xor_mac:0:4} ${xor_mac:4:4} ${xor_mac:8:4}"
+
+		xor_fw_mac=$(hexdump -v -n 6 -s $mac_offset -e '/1 "%02x"' /lib/firmware/$FIRMWARE)
+		xor_fw_mac="${xor_fw_mac:0:4} ${xor_fw_mac:4:4} ${xor_fw_mac:8:4}"
+
+		xor_fw_chksum=$(hexdump -v -n 2 -s $chksum_offset -e '/1 "%02x"' /lib/firmware/$FIRMWARE)
+		xor_fw_chksum=$(xor $xor_fw_chksum $xor_fw_mac $xor_mac)
+
+		printf "%b" "\x${xor_fw_chksum:0:2}\x${xor_fw_chksum:2:2}" | \
+			dd of=/lib/firmware/$FIRMWARE conv=notrunc bs=1 seek=$chksum_offset count=2
+	}
+
+	macaddr_2bin $mac | dd of=/lib/firmware/$FIRMWARE conv=notrunc bs=1 seek=$mac_offset count=6
+}
+
+ath9k_patch_fw_mac_crc() {
+	local mac=$1
+	local mac_offset=$2
+	local chksum_offset=$((mac_offset - 10))
+
+	ath9k_patch_fw_mac "${mac}" "${mac_offset}" "${chksum_offset}"
+}
+
 board=$(board_name)
 
 case "$FIRMWARE" in