ath: Add function to check if 4.9GHz channels are allowed

This adds a helper function to ath/regd.c which can be asked if 4.9GHz channels
are allowed for a given regulatory domain code. This keeps the knowledge of
regdomains and defines like MKK9_MKKC in one place. I'm passing the regdomain
code instead of the ath_regulatory structure because this needs to be called
quite early in the driver inititalization where ath_regulatory is not available
yet in ath5k.

I'm using MKK9_MKKC only because this is the regdomain in the 802.11j enabled
sample cards we got from our vendor. I found some hints in HAL code that this
is used by Atheros to indicate 4.9GHz channels support and that there might be
other domain codes as well, but as I don't have any documentation I'm just
putting in what I need right now. It can be extended later.
Signed-off-by: NBruno Randolf <br1@einfach.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/regd.c

@@ -158,6 +158,13 @@ ieee80211_regdomain *ath_world_regdomain(struct ath_regulatory *reg)
 	}
 }
 
+bool ath_is_49ghz_allowed(u16 regdomain)
+{
+	/* possibly more */
+	return regdomain == MKK9_MKKC;
+}
+EXPORT_SYMBOL(ath_is_49ghz_allowed);
+
 /* Frequency is one where radar detection is required */
 static bool ath_is_radar_freq(u16 center_freq)
 {

drivers/net/wireless/ath/regd.h

@@ -250,6 +250,7 @@ enum CountryCode {
 };
 
 bool ath_is_world_regd(struct ath_regulatory *reg);
+bool ath_is_49ghz_allowed(u16 redomain);
 int ath_regd_init(struct ath_regulatory *reg, struct wiphy *wiphy,
 		  int (*reg_notifier)(struct wiphy *wiphy,
 		  struct regulatory_request *request));