nl80211: advertise maximum remain-on-channel duration

With the upcoming hardware offload implementation,
some devices will have a different maximum duration
for the remain-on-channel command. Advertise the
maximum duration in mac80211, and make mac80211 set
it.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/linux/nl80211.h

@@ -773,6 +773,9 @@ enum nl80211_commands {
  *	cache, a wiphy attribute.
  *
  * @NL80211_ATTR_DURATION: Duration of an operation in milliseconds, u32.
+ * @NL80211_ATTR_MAX_REMAIN_ON_CHANNEL_DURATION: Device attribute that
+ *	specifies the maximum duration that can be requested with the
+ *	remain-on-channel operation, in milliseconds, u32.
  *
  * @NL80211_ATTR_COOKIE: Generic 64-bit cookie to identify objects.
  *
@@ -1035,6 +1038,8 @@ enum nl80211_attrs {
 
 	NL80211_ATTR_KEY_DEFAULT_TYPES,
 
+	NL80211_ATTR_MAX_REMAIN_ON_CHANNEL_DURATION,
+
 	/* add attributes here, update the policy in nl80211.c */
 
 	__NL80211_ATTR_AFTER_LAST,

include/net/cfg80211.h

@@ -1474,6 +1474,9 @@ struct ieee80211_txrx_stypes {
  *
  * @available_antennas: bitmap of antennas which are available to configure.
  *	antenna configuration commands will be rejected unless this is set.
+ *
+ * @max_remain_on_channel_duration: Maximum time a remain-on-channel operation
+ *	may request, if implemented.
  */
 struct wiphy {
 	/* assign these fields before you register the wiphy */
@@ -1511,6 +1514,8 @@ struct wiphy {
 	char fw_version[ETHTOOL_BUSINFO_LEN];
 	u32 hw_version;
 
+	u16 max_remain_on_channel_duration;
+
 	u8 max_num_pmkids;
 
 	u32 available_antennas;

net/mac80211/main.c

@@ -745,6 +745,8 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 		}
 	}
 
+	local->hw.wiphy->max_remain_on_channel_duration = 5000;
+
 	result = wiphy_register(local->hw.wiphy);
 	if (result < 0)
 		goto fail_wiphy_register;

net/wireless/nl80211.c

@@ -755,6 +755,10 @@ static int nl80211_send_wiphy(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 
 	nla_nest_end(msg, nl_cmds);
 
+	if (dev->ops->remain_on_channel)
+		NLA_PUT_U32(msg, NL80211_ATTR_MAX_REMAIN_ON_CHANNEL_DURATION,
+			    dev->wiphy.max_remain_on_channel_duration);
+
 	/* for now at least assume all drivers have it */
 	if (dev->ops->mgmt_tx)
 		NLA_PUT_FLAG(msg, NL80211_ATTR_OFFCHANNEL_TX_OK);
@@ -4228,7 +4232,8 @@ static int nl80211_remain_on_channel(struct sk_buff *skb,
 	 * We should be on that channel for at least one jiffie,
 	 * and more than 5 seconds seems excessive.
 	 */
-	if (!duration || !msecs_to_jiffies(duration) || duration > 5000)
+	if (!duration || !msecs_to_jiffies(duration) ||
+	    duration > rdev->wiphy.max_remain_on_channel_duration)
 		return -EINVAL;
 
 	if (!rdev->ops->remain_on_channel)