mac80211: inform drivers about the off-channel status on channel changes

For some drivers it can be useful to know whether the channel they're
supposed to switch to is going to be used for short off-channel work or
scanning, or whether the hardware is expected to stay on it for a while
longer. This is important for various kinds of calibration work, which
takes longer to complete and should keep some persistent state, even if
the channel temporarily changes.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/mac80211.h

@@ -625,11 +625,14 @@ struct ieee80211_rx_status {
  *	may turn the device off as much as possible. Typically, this flag will
  *	be set when an interface is set UP but not associated or scanning, but
  *	it can also be unset in that case when monitor interfaces are active.
+ * @IEEE80211_CONF_OFFCHANNEL: The device is currently not on its main
+ *	operating channel.
  */
 enum ieee80211_conf_flags {
 	IEEE80211_CONF_MONITOR		= (1<<0),
 	IEEE80211_CONF_PS		= (1<<1),
 	IEEE80211_CONF_IDLE		= (1<<2),
+	IEEE80211_CONF_OFFCHANNEL	= (1<<3),
 };
 
 

net/mac80211/main.c

@@ -107,12 +107,15 @@ int ieee80211_hw_config(struct ieee80211_local *local, u32 changed)
 	if (scan_chan) {
 		chan = scan_chan;
 		channel_type = NL80211_CHAN_NO_HT;
+		local->hw.conf.flags |= IEEE80211_CONF_OFFCHANNEL;
 	} else if (local->tmp_channel) {
 		chan = scan_chan = local->tmp_channel;
 		channel_type = local->tmp_channel_type;
+		local->hw.conf.flags |= IEEE80211_CONF_OFFCHANNEL;
 	} else {
 		chan = local->oper_channel;
 		channel_type = local->_oper_channel_type;
+		local->hw.conf.flags &= ~IEEE80211_CONF_OFFCHANNEL;
 	}
 
 	if (chan != local->hw.conf.channel ||