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From:   Sonny Sasaka <sonnysasaka@chromium.org>
To:     linux-bluetooth@vger.kernel.org
Cc:     Sonny Sasaka <sonnysasaka@chromium.org>,
        Alain Michaud <alainm@chromium.org>
Subject: [PATCH BlueZ v2 2/2] input/hog: Cache the HID report map
Date:   Fri, 11 Dec 2020 15:30:47 -0800
Message-Id: <20201211233047.108658-2-sonnysasaka@chromium.org>
In-Reply-To: <20201211233047.108658-1-sonnysasaka@chromium.org>
References: <20201211233047.108658-1-sonnysasaka@chromium.org>
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To optimize BLE HID devices reconnection response, we can cache the
report map so that the subsequent reconnections do not need round trip
time to read the report map.

Reviewed-by: Alain Michaud <alainm@chromium.org>

---
 profiles/input/hog-lib.c | 142 ++++++++++++++++++++++++++++++++-------
 1 file changed, 118 insertions(+), 24 deletions(-)

diff --git a/profiles/input/hog-lib.c b/profiles/input/hog-lib.c
index ee811d301..e5fef4c7c 100644
--- a/profiles/input/hog-lib.c
+++ b/profiles/input/hog-lib.c
@@ -95,6 +95,13 @@ struct bt_hog {
 	struct queue		*bas;
 	GSList			*instances;
 	struct queue		*gatt_op;
+	struct gatt_db		*gatt_db;
+	struct gatt_db_attribute	*report_map_attr;
+};
+
+struct report_map {
+	uint8_t	value[HOG_REPORT_MAP_MAX_SIZE];
+	size_t	length;
 };
 
 struct report {
@@ -924,33 +931,16 @@ static char *item2string(char *str, uint8_t *buf, uint8_t len)
 	return str;
 }
 
-static void report_map_read_cb(guint8 status, const guint8 *pdu, guint16 plen,
-							gpointer user_data)
+static void uhid_create(struct bt_hog *hog, uint8_t *report_map,
+							ssize_t report_map_len)
 {
-	struct gatt_request *req = user_data;
-	struct bt_hog *hog = req->user_data;
-	uint8_t value[HOG_REPORT_MAP_MAX_SIZE];
+	uint8_t *value = report_map;
 	struct uhid_event ev;
-	ssize_t vlen;
+	ssize_t vlen = report_map_len;
 	char itemstr[20]; /* 5x3 (data) + 4 (continuation) + 1 (null) */
 	int i, err;
 	GError *gerr = NULL;
 
-	destroy_gatt_req(req);
-
-	DBG("HoG inspecting report map");
-
-	if (status != 0) {
-		error("Report Map read failed: %s", att_ecode2str(status));
-		return;
-	}
-
-	vlen = dec_read_resp(pdu, plen, value, sizeof(value));
-	if (vlen < 0) {
-		error("ATT protocol error");
-		return;
-	}
-
 	DBG("Report MAP:");
 	for (i = 0; i < vlen;) {
 		ssize_t ilen = 0;
@@ -1022,6 +1012,43 @@ static void report_map_read_cb(guint8 status, const guint8 *pdu, guint16 plen,
 	DBG("HoG created uHID device");
 }
 
+static void db_report_map_write_value_cb(struct gatt_db_attribute *attr,
+						int err, void *user_data)
+{
+	if (err)
+		error("Error writing report map value to gatt db");
+}
+
+static void report_map_read_cb(guint8 status, const guint8 *pdu, guint16 plen,
+							gpointer user_data)
+{
+	struct gatt_request *req = user_data;
+	struct bt_hog *hog = req->user_data;
+	uint8_t value[HOG_REPORT_MAP_MAX_SIZE];
+	ssize_t vlen;
+
+	destroy_gatt_req(req);
+
+	DBG("HoG inspecting report map");
+
+	if (status != 0) {
+		error("Report Map read failed: %s", att_ecode2str(status));
+		return;
+	}
+
+	vlen = dec_read_resp(pdu, plen, value, sizeof(value));
+	if (vlen < 0) {
+		error("ATT protocol error");
+		return;
+	}
+
+	uhid_create(hog, value, vlen);
+
+	/* Cache the report map to optimize reconnection */
+	gatt_db_attribute_write(hog->report_map_attr, 0, value, vlen, 0, NULL,
+					db_report_map_write_value_cb, NULL);
+}
+
 static void info_read_cb(guint8 status, const guint8 *pdu, guint16 plen,
 							gpointer user_data)
 {
@@ -1269,12 +1296,32 @@ static void foreach_hog_external(struct gatt_db_attribute *attr,
 					external_report_reference_cb, hog);
 }
 
+static void db_report_map_read_value_cb(struct gatt_db_attribute *attrib,
+						int err, const uint8_t *value,
+						size_t length, void *user_data)
+{
+	struct report_map *map = user_data;
+
+	if (err) {
+		error("Error reading report map from gatt db %s",
+								strerror(-err));
+		return;
+	}
+
+	if (!length)
+		return;
+
+	map->length = length < sizeof(map->value) ? length : sizeof(map->value);
+	memcpy(map->value, value, map->length);
+}
+
 static void foreach_hog_chrc(struct gatt_db_attribute *attr, void *user_data)
 {
 	struct bt_hog *hog = user_data;
 	bt_uuid_t uuid, report_uuid, report_map_uuid, info_uuid;
 	bt_uuid_t proto_mode_uuid, ctrlpt_uuid;
 	uint16_t handle, value_handle;
+	struct report_map report_map = {0};
 
 	gatt_db_attribute_get_char_data(attr, &handle, &value_handle, NULL,
 					NULL, &uuid);
@@ -1288,8 +1335,24 @@ static void foreach_hog_chrc(struct gatt_db_attribute *attr, void *user_data)
 
 	bt_uuid16_create(&report_map_uuid, HOG_REPORT_MAP_UUID);
 	if (!bt_uuid_cmp(&report_map_uuid, &uuid)) {
-		read_char(hog, hog->attrib, value_handle, report_map_read_cb,
-									hog);
+
+		hog->report_map_attr = gatt_db_get_attribute(hog->gatt_db,
+								value_handle);
+		gatt_db_attribute_read(hog->report_map_attr, 0,
+					BT_ATT_OP_READ_REQ, NULL,
+					db_report_map_read_value_cb,
+					&report_map);
+
+		if (report_map.length) {
+			/* Report map found in the cache, straight to creating
+			 * UHID to optimize reconnection.
+			 */
+			uhid_create(hog, report_map.value, report_map.length);
+		} else {
+			read_char(hog, hog->attrib, value_handle,
+						report_map_read_cb, hog);
+		}
+
 		gatt_db_service_foreach_desc(attr, foreach_hog_external, hog);
 		return;
 	}
@@ -1417,6 +1480,8 @@ struct bt_hog *bt_hog_new(int fd, const char *name, uint16_t vendor,
 			hog->dis = bt_dis_new(db);
 			bt_dis_set_notification(hog->dis, dis_notify, hog);
 		}
+
+		hog->gatt_db = db;
 	}
 
 	return bt_hog_ref(hog);
@@ -1612,9 +1677,14 @@ bool bt_hog_attach(struct bt_hog *hog, void *gatt)
 					hog->primary->range.start,
 					hog->primary->range.end, NULL,
 					char_discovered_cb, hog);
-		return true;
 	}
 
+	if (!hog->uhid_created)
+		return true;
+
+	/* If UHID is already created, set up the report value handlers to
+	 * optimize reconnection.
+	 */
 	for (l = hog->reports; l; l = l->next) {
 		struct report *r = l->data;
 
@@ -1627,6 +1697,29 @@ bool bt_hog_attach(struct bt_hog *hog, void *gatt)
 	return true;
 }
 
+static void uhid_destroy(struct bt_hog *hog)
+{
+	int err;
+	struct uhid_event ev;
+
+	if (!hog->uhid_created)
+		return;
+
+	bt_uhid_unregister_all(hog->uhid);
+
+	memset(&ev, 0, sizeof(ev));
+	ev.type = UHID_DESTROY;
+
+	err = bt_uhid_send(hog->uhid, &ev);
+
+	if (err < 0) {
+		error("bt_uhid_send: %s", strerror(-err));
+		return;
+	}
+
+	hog->uhid_created = false;
+}
+
 void bt_hog_detach(struct bt_hog *hog)
 {
 	GSList *l;
@@ -1660,6 +1753,7 @@ void bt_hog_detach(struct bt_hog *hog)
 	queue_foreach(hog->gatt_op, (void *) cancel_gatt_req, NULL);
 	g_attrib_unref(hog->attrib);
 	hog->attrib = NULL;
+	uhid_destroy(hog);
 }
 
 int bt_hog_set_control_point(struct bt_hog *hog, bool suspend)
-- 
2.26.2