HID: hid-sensor-hub: Add support for application collection

Section 4.2.5 of HID Sensor hub specification allows two methods
defining sensor devices.
- Each sensor device by its own collection
- A top level application collection object, including multiple
sensors.
In the first method, each sensor can be in its own sensor application
collection without a physical collection.
In the second method there is a usage id for collection type, which
is defined as an application collection, with multiple physical
collections in it. It is possible to define fusion sensor with this
and may have its own handler. If there is a callback registered
for the collection type, then forward all reports for sensors in
its collection to this handler.

Signed-off-by: Srinivas Pandruvada <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/hid-sensor-hub.c

···
 
 	for (i = 0; i < hdev->maxcollection; ++i) {
 		struct hid_collection *collection = &hdev->collection[i];
-		if (collection->type == HID_COLLECTION_PHYSICAL)
+		if (collection->type == HID_COLLECTION_PHYSICAL ||
+		    collection->type == HID_COLLECTION_APPLICATION)
 			++count;
 	}
 
···
 
 	spin_lock(&pdata->dyn_callback_lock);
 	list_for_each_entry(callback, &pdata->dyn_callback_list, list)
-		if (callback->usage_id == usage_id &&
+		if ((callback->usage_id == usage_id ||
+		     callback->usage_id == HID_USAGE_SENSOR_COLLECTION) &&
 			(collection_index >=
 				callback->hsdev->start_collection_index) &&
 			(collection_index <
···
 	callback->usage_callback = usage_callback;
 	callback->usage_id = usage_id;
 	callback->priv = NULL;
-	list_add_tail(&callback->list, &pdata->dyn_callback_list);
+	/*
+	 * If there is a handler registered for the collection type, then
+	 * it will handle all reports for sensors in this collection. If
+	 * there is also an individual sensor handler registration, then
+	 * we want to make sure that the reports are directed to collection
+	 * handler, as this may be a fusion sensor. So add collection handlers
+	 * to the beginning of the list, so that they are matched first.
+	 */
+	if (usage_id == HID_USAGE_SENSOR_COLLECTION)
+		list_add(&callback->list, &pdata->dyn_callback_list);
+	else
+		list_add_tail(&callback->list, &pdata->dyn_callback_list);
 	spin_unlock_irqrestore(&pdata->dyn_callback_lock, flags);
 
 	return 0;
···
 	int dev_cnt;
 	struct hid_sensor_hub_device *hsdev;
 	struct hid_sensor_hub_device *last_hsdev = NULL;
+	struct hid_sensor_hub_device *collection_hsdev = NULL;
 
 	sd = devm_kzalloc(&hdev->dev, sizeof(*sd), GFP_KERNEL);
 	if (!sd) {
···
 	for (i = 0; i < hdev->maxcollection; ++i) {
 		struct hid_collection *collection = &hdev->collection[i];
 
-		if (collection->type == HID_COLLECTION_PHYSICAL) {
+		if (collection->type == HID_COLLECTION_PHYSICAL ||
+		    collection->type == HID_COLLECTION_APPLICATION) {
 
 			hsdev = devm_kzalloc(&hdev->dev, sizeof(*hsdev),
 					     GFP_KERNEL);
···
 			hid_dbg(hdev, "Adding %s:%d\n", name,
 					hsdev->start_collection_index);
 			sd->hid_sensor_client_cnt++;
+			if (collection_hsdev)
+				collection_hsdev->end_collection_index = i;
+			if (collection->type == HID_COLLECTION_APPLICATION &&
+			    collection->usage == HID_USAGE_SENSOR_COLLECTION)
+				collection_hsdev = hsdev;
 		}
 	}
 	if (last_hsdev)
 		last_hsdev->end_collection_index = i;
+	if (collection_hsdev)
+		collection_hsdev->end_collection_index = i;
 
 	ret = mfd_add_hotplug_devices(&hdev->dev,
 			sd->hid_sensor_hub_client_devs,

include/linux/hid-sensor-ids.h

···
 
 #define HID_MAX_PHY_DEVICES					0xFF
 
+#define HID_USAGE_SENSOR_COLLECTION				0x200001
+
 /* Accel 3D (200073) */
 #define HID_USAGE_SENSOR_ACCEL_3D				0x200073
 #define HID_USAGE_SENSOR_DATA_ACCELERATION			0x200452