[PATCH v2 2/4] knownnetworks: sort known frequencies by BSS rank

[James Prestwood <prestwoj@gmail.com>]

Currently a quick scan uses the entire known frequency list so
ordering really doesn't matter but improvements will be made here
to make quick scans "quicker" for large network deployments (with
many known frequencies).

To prepare for this the known frequency list has been changed to
be sorted by BSS rank rather than most recently seen. This makes
a lot more sense because IWD should prefer to scan frequencies
that had higher ranked BSS's, not just frequencies that were scanned
last on the most recent scan.

As far as the disk sync goes the ranking is not included, but
ordering is. This really isn't a limitation because when IWD starts
up there isn't any guarantee its in the same physical location so
old scan ranks are likely not valid anymore. The first set of scans
will begin replacing the frequencies loaded from disk.
---
 src/knownnetworks.c | 16 ++++++++++++++--
 src/knownnetworks.h |  1 +
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/knownnetworks.c b/src/knownnetworks.c
index f6284fdc..6e549e02 100644
--- a/src/knownnetworks.c
+++ b/src/knownnetworks.c
@@ -562,9 +562,19 @@ static bool known_frequency_match(const void *a, const void *b)
 	return known_freq->frequency == *frequency;
 }
 
+static int known_frequency_compare(const void *a, const void *b,
+					void *user_data)
+{
+	const struct known_frequency *kf_a = a;
+	const struct known_frequency *kf_b = b;
+
+	return (kf_b->rank > kf_a->rank) ? 1 : -1;
+}
+
 /*
  * Adds a frequency to the 'known' set of frequencies that this network
- * operates on.  The list is sorted according to most-recently seen
+ * operates on.  The list is sorted according to the rank of the BSS on that
+ * frequency.
  */
 int known_network_add_frequency(struct network_info *info, struct scan_bss *bss)
 {
@@ -578,9 +588,11 @@ int known_network_add_frequency(struct network_info *info, struct scan_bss *bss)
 	if (!known_freq) {
 		known_freq = l_new(struct known_frequency, 1);
 		known_freq->frequency = bss->frequency;
+		known_freq->rank = bss->rank;
 	}
 
-	l_queue_push_head(info->known_frequencies, known_freq);
+	l_queue_insert(info->known_frequencies, known_freq,
+			known_frequency_compare, NULL);
 
 	return 0;
 }
diff --git a/src/knownnetworks.h b/src/knownnetworks.h
index 9f81e308..36106501 100644
--- a/src/knownnetworks.h
+++ b/src/knownnetworks.h
@@ -96,6 +96,7 @@ typedef void (*known_networks_destroy_func_t)(void *user_data);
 
 struct known_frequency {
 	uint32_t frequency;
+	uint16_t rank;
 };
 
 void __network_config_parse(const struct l_settings *settings,
-- 
2.34.1