[source] ar71xx: Do not use a hardcoded ath10k firmware mac address

[LEDE Commits]

nbd pushed a commit to source.git, branch master:
https://git.lede-project.org/e7be0decf65a2d3ecbe344bcb172151516815935

commit e7be0decf65a2d3ecbe344bcb172151516815935
Author: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
AuthorDate: Sun Sep 18 23:29:35 2016 +0200

    ar71xx: Do not use a hardcoded ath10k firmware mac address
    
    ar71xx has an init-script for special devices where the ath10k OTP
    calibration data is stored on the PCIe card's EEPROM (and thus can only
    be read by ath10k). Unfortunately the OTP data uses the default mac
    address (= all devices come with the same mac address, which leads to
    problems when you have multiple of these devices in the same network).
    
    To work around this the mac address is patched in the firmware during
    the first boot of the device. To prevent flash wear this was only done
    if the ath10k firmware matched a hardcoded md5sum.
    However, if the md5sum does not match this can mean that either the mac
    address was already patched (which is fine) - unfortunately it can also
    mean that the firmware version was updated without updating the
    hardcoded md5sum.
    
    Change the "was the mac address already patched" check to actually
    compare the mac address inside the ath10k firmware.
    
    Signed-off-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
---
 .../linux/ar71xx/base-files/lib/preinit/82_patch_ath10k | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/target/linux/ar71xx/base-files/lib/preinit/82_patch_ath10k b/target/linux/ar71xx/base-files/lib/preinit/82_patch_ath10k
index af12bd5..b6af921 100644
--- a/target/linux/ar71xx/base-files/lib/preinit/82_patch_ath10k
+++ b/target/linux/ar71xx/base-files/lib/preinit/82_patch_ath10k
@@ -12,16 +12,19 @@ do_patch_ath10k_firmware() {
 		return
 	}
 
-	local firmware_md5_orig="fcb2fbd42d73a63fbf603505c718cbde"
-	local firmware_md5_current="$(md5sum $firmware_file)"
-	local firmware_md5_current="${firmware_md5_current%% *}"
+	local mac_offset=276
+	local mac_length=6
+	local default_mac="00:03:07:12:34:56"
+	local current_mac="$(hexdump -v -n $mac_length -s $mac_offset -e '5/1 "%02x:" 1/1 "%02x"' $firmware_file  2>/dev/null)"
 
-	# verify md5sum before patching
-	[ "$firmware_md5_orig" != "$firmware_md5_current" ] || {
+	# check if mac address was already patched
+	[ "$default_mac" = "$current_mac" ] || {
 		return
 	}
 
-	# some boards have bogus mac in otp, patch the default mac in the firmware
+	# some boards have bogus mac in otp (= directly in the PCIe card's EEPROM).
+	# we have to patch the default mac in the firmware because we cannot change
+	# the otp.
 	case $(ar71xx_board_name) in
 		dgl-5500-a1 | tew-823dru)
 			local mac
@@ -29,7 +32,7 @@ do_patch_ath10k_firmware() {
 
 			cp $firmware_file /tmp/ath10k-firmware.bin
 			macaddr_2bin $mac | dd of=/tmp/ath10k-firmware.bin \
-				conv=notrunc bs=1 seek=276 count=6
+				conv=notrunc bs=1 seek=$mac_offset count=$mac_length
 
 		;;
 	esac