[PATCH BlueZ] adapter: Use regular discovery for filters which only have discoverable set

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discovery_filter_to_mgmt_cp() does not add discovery_filter.discoverable
to the created mgmt_cp_start_service_discovery struct.

Instead update_discovery_filter() seprately checks
client->discovery_filter->discoverable for all clients.

This means that for discovery-filters which only have the discoverable
flag set, to put the adapter in discoverable mode while discovering,
the created mgmt_cp_start_service_discovery struct is empty.

This empty mgmt_cp_start_service_discovery struct then gets send
to the kernel as part of a MGMT_OP_START_SERVICE_DISCOVERY msg
by start_discovery_timeout().

This use of an empty filter with MGMT_OP_START_SERVICE_DISCOVERY
causes some bluetooth devices to not get seen with some (most?)
Broadcom bluetooth adapters. This problem has been observed with
the following Broadcom models: BCM4343A0, BCM43430A1, BCM43341B0 .

On these models the following 2 devices were not being discovered
when starting a scan with a filter with just discoverable set
in the filter (as gnome-bluetooth does):

Device 09:02:01:03:0F:87 (public)
	Name: Bluetooth 3.0 Keyboard
	Alias: Bluetooth 3.0 Keyboard
	Class: 0x00000540
	Icon: input-keyboard
	Paired: yes
	Bonded: yes
	Trusted: yes
	Blocked: no
	Connected: yes
	WakeAllowed: yes
	LegacyPairing: yes
	UUID: Service Discovery Serve.. (00001000-0000-1000-8000-00805f9b34fb)
	UUID: Human Interface Device... (00001124-0000-1000-8000-00805f9b34fb)
	UUID: PnP Information           (00001200-0000-1000-8000-00805f9b34fb)
	Modalias: bluetooth:v05ACp022Cd011B

Device 00:60:D1:00:00:34 (public)
	Name: Bluetooth Mouse
	Alias: Bluetooth Mouse
	Class: 0x00002580
	Icon: input-mouse
	Paired: yes
	Bonded: yes
	Trusted: yes
	Blocked: no
	Connected: yes
	WakeAllowed: yes
	LegacyPairing: no
	UUID: Human Interface Device... (00001124-0000-1000-8000-00805f9b34fb)
	UUID: PnP Information           (00001200-0000-1000-8000-00805f9b34fb)
	Modalias: usb:v0103p0204d001E

Since setting the discoverable flag on a filter only is a way to
automatically put the adapter in discoverable mode itself while
it is discovering; and since this does not any device filtering
at all; modify merge_discovery_filters() to treat discovery with
such filters as regular unfiltered discovery.

This results in start_discovery_timeout() starting regular
discovery through a MGMT_OP_START_DISCOVERY message and this
fixes these 2 example devices not getting discovered by the
mentioned Broadcom BT adapter models.

Link: https://gitlab.gnome.org/GNOME/gnome-bluetooth/-/merge_requests/163
Note the same argument can be made for the pattern and duplicate part of
the filters which also get handled outside of the kernel filter.
But I prefer to keep the first patch small and targetted at solving things
not working with the gnome-bluetooth filter settings.

Also I'm not familiar enough with the code to say with certainty that
filters with just a pattern or the duplicate flag set (or a combination)
should also be treated as unfiltered discovery.
 src/adapter.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/adapter.c b/src/adapter.c
index 7947160a6..cc7f891d9 100644
--- a/src/adapter.c
+++ b/src/adapter.c
@@ -2192,6 +2192,7 @@ static int merge_discovery_filters(struct btd_adapter *adapter, int *rssi,
 	bool empty_uuid = false;
 	bool has_regular_discovery = false;
 	bool has_filtered_discovery = false;
+	uint8_t adapter_scan_type = get_scan_type(adapter);
 	for (l = adapter->discovery_list; l != NULL; l = g_slist_next(l)) {
 		struct discovery_client *client = l->data;
@@ -2202,6 +2203,20 @@ static int merge_discovery_filters(struct btd_adapter *adapter, int *rssi,
+		/*
+		 * Detect empty filter with only discoverable
+		 * (which does not require a kernel filter) set.
+		 */
+		if (item->uuids == NULL &&
+		    item->pathloss == DISTANCE_VAL_INVALID &&
+		    item->rssi == DISTANCE_VAL_INVALID &&
+		    item->type == adapter_scan_type &&
+		    item->duplicate == false &&
+		    item->pattern == NULL) {
+			has_regular_discovery = true;
+			continue;
+		}
 		has_filtered_discovery = true;
 		*transport |= item->type;
@@ -2251,7 +2266,7 @@ static int merge_discovery_filters(struct btd_adapter *adapter, int *rssi,
 		 * It there is both regular and filtered scan running, then
 		 * clear whole fitler to report all devices.
-		*transport = get_scan_type(adapter);
+		*transport = adapter_scan_type;
 		*rssi = HCI_RSSI_INVALID;
 		*uuids = NULL;

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