mpc85xx: add migration script for TP-Link TL-WDR4900 v1 WLAN PCI paths

PCI paths of the WLAN devices have changed between kernel 4.4 and 4.9;
migrate config so existing wifi-iface definitions don't break.

This is implemented as a hotplug handler rather than a uci-defaults script
as the migration script must run before the 10-wifi-detect hotplug handler.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
(cherry picked from commit b452af23a8)

target/linux/mpc85xx/base-files/etc/hotplug.d/ieee80211/05-wifi-migrate

@@ -0,0 +1,63 @@
+#!/bin/sh
+
+# This must run before 10-wifi-detect
+
+
+[ "${ACTION}" = "add" ] || return
+
+
+. /lib/functions.sh
+
+
+check_radio()
+{
+	local cfg="$1" to="$2"
+
+	config_get path "$cfg" path
+
+	[ "$path" = "$to" ] && PATH_EXISTS=true
+}
+
+do_migrate_radio()
+{
+	local cfg="$1" from="$2" to="$3"
+
+	config_get path "$cfg" path
+
+	[ "$path" = "$from" ] || return
+
+	uci set "wireless.${cfg}.path=${to}"
+	WIRELESS_CHANGED=true
+
+	logger -t wifi-migrate "Updated path of wireless.${cfg} from '${from}' to '${to}'"
+}
+
+migrate_radio()
+{
+	local from="$1" to="$2"
+
+	config_load wireless
+
+	# Check if there is already a section with the target path: In this case, the system
+	# was already upgraded to a version without this migration script before; better bail out,
+	# as we can't be sure we don't break more than we fix.
+	PATH_EXISTS=false
+	config_foreach check_radio wifi-device "$to"
+	$PATH_EXISTS && return
+
+	config_foreach do_migrate_radio wifi-device "$from" "$to"
+}
+
+
+WIRELESS_CHANGED=false
+
+case "$(board_name)" in
+tplink,tl-wdr4900-v1)
+	migrate_radio 'ffe09000.pcie/pci0000:00/0000:00:00.0/0000:01:00.0' 'ffe09000.pcie/pci9000:00/9000:00:00.0/9000:01:00.0'
+	migrate_radio 'ffe0a000.pcie/pci0001:02/0001:02:00.0/0001:03:00.0' 'ffe0a000.pcie/pcia000:02/a000:02:00.0/a000:03:00.0'
+	;;
+esac
+
+$WIRELESS_CHANGED && uci commit wireless
+
+exit 0