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>
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 53f0443..594a6ac 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -755,6 +755,10 @@
 
 	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 @@
 	 * 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)