HID: core: simplify active collection tracking

Manually tracking an active collection to set collection parents is not
necessary, we just have to look one step back into the collection stack
to find the correct parent.
Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

drivers/hid/hid-core.c

@@ -173,8 +173,8 @@ static int open_collection(struct hid_parser *parser, unsigned type)
 	collection->type = type;
 	collection->usage = usage;
 	collection->level = parser->collection_stack_ptr - 1;
-	collection->parent_idx = parser->active_collection_idx;
-	parser->active_collection_idx = collection_index;
+	collection->parent_idx = (collection->level == 0) ? -1 :
+		parser->collection_stack[collection->level - 1];
 
 	if (type == HID_COLLECTION_APPLICATION)
 		parser->device->maxapplication++;
@@ -193,13 +193,6 @@ static int close_collection(struct hid_parser *parser)
 		return -EINVAL;
 	}
 	parser->collection_stack_ptr--;
-	if (parser->active_collection_idx != -1) {
-		struct hid_device *device = parser->device;
-		struct hid_collection *c;
-
-		c = &device->collection[parser->active_collection_idx];
-		parser->active_collection_idx = c->parent_idx;
-	}
 	return 0;
 }
 
@@ -825,7 +818,6 @@ static int hid_scan_report(struct hid_device *hid)
 		return -ENOMEM;
 
 	parser->device = hid;
-	parser->active_collection_idx = -1;
 	hid->group = HID_GROUP_GENERIC;
 
 	/*
@@ -1179,7 +1171,6 @@ int hid_open_report(struct hid_device *device)
 	}
 
 	parser->device = device;
-	parser->active_collection_idx = -1;
 
 	end = start + size;
 

include/linux/hid.h

@@ -658,7 +658,6 @@ struct hid_parser {
 	unsigned int         *collection_stack;
 	unsigned int          collection_stack_ptr;
 	unsigned int          collection_stack_size;
-	int                   active_collection_idx; /* device->collection */
 	struct hid_device    *device;
 	unsigned int          scan_flags;
 };