[RFC] cfg80211: expose cfg80211_disable_40mhz_24ghz module parameter

[Arend van Spriel <arend@broadcom.com>]

Drivers may need to know this variable value for configuring the
device they are controlling. It can be determined indirectly by
setting IEEE80211_HT_CAP_SUP_WIDTH_20_40 flag in the field
ieee80211_sta_htcap::cap of 2G band. During the wiphy_register()
call cfg80211 will clear that bit if the module parameter is true.
However, brcmfmac for one needs to know the value to determine
its custom regulatory domain which must be applied before doing
the wiphy_register().

Cc: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Daniel (Deognyoun) Kim <dekim@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
---
Hi Johannes,

In brcmfmac I need to know the value of cfg80211 module parameter
as stated in the commit message. Just taking a shot at how to get
this exposed. I was reluctant exporting the module parameter itself.

Regards,
Arend
---
 include/net/cfg80211.h |    9 +++++++++
 net/wireless/core.c    |    6 ++++++
 2 files changed, 15 insertions(+)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index f3539a1..9279197 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -3107,6 +3107,15 @@ static inline const char *wiphy_name(const struct wiphy *wiphy)
 struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv);
 
 /**
+ * wiphy_is_40mhz_24ghz_disabled - check whether 40MHz bandwidth in 2.4G
+ *
+ * @wiphy: The wiphy to check.
+ *
+ * Return: true is 40MHz is disabled in 2.4G band.
+ */
+bool wiphy_is_40mhz_24ghz_disabled(struct wiphy *wiphy);
+
+/**
  * wiphy_register - register a wiphy with cfg80211
  *
  * @wiphy: The wiphy to register.
diff --git a/net/wireless/core.c b/net/wireless/core.c
index 086cddd..52750ef 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -355,6 +355,12 @@ struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv)
 }
 EXPORT_SYMBOL(wiphy_new);
 
+bool wiphy_is_40mhz_24ghz_disabled(struct wiphy *wiphy)
+{
+	return cfg80211_disable_40mhz_24ghz;
+}
+EXPORT_SYMBOL(wiphy_is_40mhz_24ghz_disabled);
+
 static int wiphy_verify_combinations(struct wiphy *wiphy)
 {
 	const struct ieee80211_iface_combination *c;
-- 
1.7.9.5