gluon-core: 200-wireless: upgrade 11ac radios to VHT20 (#1328)

Patch originally authored by @oleeander.

Fixes #424

package/gluon-core/Makefile

@@ -17,8 +17,8 @@ define Package/gluon-core
   CATEGORY:=Gluon
   TITLE:=Base files of Gluon
   DEPENDS:= \
-	+gluon-site +libgluonutil +lua-platform-info +lua-simple-uci +lua-hash +lua-jsonc +luci-lib-nixio \
-	+vxlan +odhcp6c +firewall +pretty-hostname
+	+gluon-site +libgluonutil +libiwinfo-lua +lua-platform-info +lua-simple-uci +lua-hash +lua-jsonc \
+	+luci-lib-nixio +vxlan +odhcp6c +firewall +pretty-hostname
 endef
 
 define Package/gluon-core/description

package/gluon-core/luasrc/lib/gluon/upgrade/200-wireless

@@ -3,6 +3,7 @@
 local util = require 'gluon.util'
 local site = require 'gluon.site'
 local sysconfig = require 'gluon.sysconfig'
+local iwinfo = require 'iwinfo'
 
 local uci = require('simple-uci').cursor()
 
@@ -20,6 +21,15 @@ local function get_channel(radio, config)
 	return channel or config.channel()
 end
 
+local function get_htmode(radio)
+       local phy = util.find_phy(radio)
+       if iwinfo.nl80211.hwmodelist(phy).ac then
+               return 'VHT20'
+       else
+               return 'HT20'
+       end
+end
+
 local function is_disabled(name)
 	if uci:get('wireless', name) then
 		return uci:get_bool('wireless', name, 'disabled')
@@ -152,11 +162,12 @@ util.foreach_radio(uci, function(radio, index, config)
 	end
 
 	local channel = get_channel(radio, config)
+	local htmode = get_htmode(radio)
 
 	uci:delete('wireless', radio_name, 'disabled')
 
 	uci:set('wireless', radio_name, 'channel', channel)
-	uci:set('wireless', radio_name, 'htmode', 'HT20')
+	uci:set('wireless', radio_name, 'htmode', htmode)
 	uci:set('wireless', radio_name, 'country', site.regdom())
 
 	uci:set_list('wireless', radio_name, 'supported_rates', config.supported_rates())