nl80211: add an attribute to allow delaying the first scheduled scan cycle

The userspace may want to delay the the first scheduled scan or
net-detect cycle.  Add an optional attribute to the scheduled scan
configuration to pass the delay to be (optionally) used by the driver.
Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
[add the attribute to the policy to validate it]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -1493,6 +1493,10 @@ struct cfg80211_match_set {
  * @rcu_head: RCU callback used to free the struct
  * @owner_nlportid: netlink portid of owner (if this should is a request
  *	owned by a particular socket)
+ * @delay: delay in seconds to use before starting the first scan
+ *	cycle.  The driver may ignore this parameter and start
+ *	immediately (or at any other time), if this feature is not
+ *	supported.
  */
 struct cfg80211_sched_scan_request {
 	struct cfg80211_ssid *ssids;
@@ -1506,6 +1510,7 @@ struct cfg80211_sched_scan_request {
 	struct cfg80211_match_set *match_sets;
 	int n_match_sets;
 	s32 min_rssi_thold;
+	u32 delay;
 
 	u8 mac_addr[ETH_ALEN] __aligned(2);
 	u8 mac_addr_mask[ETH_ALEN] __aligned(2);

include/uapi/linux/nl80211.h

@@ -324,7 +324,9 @@
  *	if passed, define which channels should be scanned; if not
  *	passed, all channels allowed for the current regulatory domain
  *	are used.  Extra IEs can also be passed from the userspace by
- *	using the %NL80211_ATTR_IE attribute.
+ *	using the %NL80211_ATTR_IE attribute.  The first cycle of the
+ *	scheduled scan can be delayed by %NL80211_ATTR_SCHED_SCAN_DELAY
+ *	is supplied.
  * @NL80211_CMD_STOP_SCHED_SCAN: stop a scheduled scan. Returns -ENOENT if
  *	scheduled scan is not running. The caller may assume that as soon
  *	as the call returns, it is safe to start a new scheduled scan again.
@@ -1735,6 +1737,9 @@ enum nl80211_commands {
  *	should be contained in the result as the sum of the respective counters
  *	over all channels.
  *
+ * @NL80211_ATTR_SCHED_SCAN_DELAY: delay before a scheduled scan (or a
+ *	WoWLAN net-detect scan) is started, u32 in seconds.
+ *
  * @NUM_NL80211_ATTR: total number of nl80211_attrs available
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
@@ -2100,6 +2105,8 @@ enum nl80211_attrs {
 
 	NL80211_ATTR_NETNS_FD,
 
+	NL80211_ATTR_SCHED_SCAN_DELAY,
+
 	/* add attributes here, update the policy in nl80211.c */
 
 	__NL80211_ATTR_AFTER_LAST,
@@ -3743,11 +3750,12 @@ struct nl80211_pattern_support {
  * @NL80211_WOWLAN_TRIG_NET_DETECT: wake up when a configured network
  *	is detected.  This is a nested attribute that contains the
  *	same attributes used with @NL80211_CMD_START_SCHED_SCAN.  It
- *	specifies how the scan is performed (e.g. the interval and the
- *	channels to scan) as well as the scan results that will
- *	trigger a wake (i.e. the matchsets).  This attribute is also
- *	sent in a response to @NL80211_CMD_GET_WIPHY, indicating the
- *	number of match sets supported by the driver (u32).
+ *	specifies how the scan is performed (e.g. the interval, the
+ *	channels to scan and the initial delay) as well as the scan
+ *	results that will trigger a wake (i.e. the matchsets).  This
+ *	attribute is also sent in a response to
+ *	@NL80211_CMD_GET_WIPHY, indicating the number of match sets
+ *	supported by the driver (u32).
  * @NL80211_WOWLAN_TRIG_NET_DETECT_RESULTS: nested attribute
  *	containing an array with information about what triggered the
  *	wake up.  If no elements are present in the array, it means

net/wireless/nl80211.c

@@ -398,6 +398,7 @@ static const struct nla_policy nl80211_policy[NUM_NL80211_ATTR] = {
 	[NL80211_ATTR_MAC_MASK] = { .len = ETH_ALEN },
 	[NL80211_ATTR_WIPHY_SELF_MANAGED_REG] = { .type = NLA_FLAG },
 	[NL80211_ATTR_NETNS_FD] = { .type = NLA_U32 },
+	[NL80211_ATTR_SCHED_SCAN_DELAY] = { .type = NLA_U32 },
 };
 
 /* policy for the key attributes */
@@ -6205,6 +6206,10 @@ nl80211_parse_sched_scan(struct wiphy *wiphy, struct wireless_dev *wdev,
 		}
 	}
 
+	if (attrs[NL80211_ATTR_SCHED_SCAN_DELAY])
+		request->delay =
+			nla_get_u32(attrs[NL80211_ATTR_SCHED_SCAN_DELAY]);
+
 	request->interval = interval;
 	request->scan_start = jiffies;