greybus: count rather than list protocol users

We don't really need a list of protocol users, we can just keep
track of how many there are.  Get rid of the list and use a count
instead.

Also, have gb_protocol_get() return the protocol rather than assigning
a passed-in connection pointer's protocol.  Make a comparable change
to the gb_protocol_put() interface.

Get rid of gb_protocol_find() (the version that locks), because it
is no longer needed.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/staging/greybus/connection.c

@@ -164,9 +164,9 @@ struct gb_connection *gb_connection_create(struct gb_interface *interface,
 	if (!connection)
 		return NULL;
 
-	INIT_LIST_HEAD(&connection->protocol_links);
 	/* XXX Will have to establish connections to get version */
-	if (!gb_protocol_get(connection, protocol_id, major, minor)) {
+	connection->protocol = gb_protocol_get(protocol_id, major, minor);
+	if (!connection->protocol) {
 		pr_err("protocol 0x%02hhx not found\n", protocol_id);
 		kfree(connection);
 		return NULL;
@@ -175,7 +175,7 @@ struct gb_connection *gb_connection_create(struct gb_interface *interface,
 	hd = interface->gmod->hd;
 	connection->hd = hd;
 	if (!gb_connection_hd_cport_id_alloc(connection)) {
-		gb_protocol_put(connection);
+		gb_protocol_put(connection->protocol);
 		kfree(connection);
 		return NULL;
 	}
@@ -198,7 +198,7 @@ struct gb_connection *gb_connection_create(struct gb_interface *interface,
 		pr_err("failed to add connection device for cport 0x%04hx\n",
 			cport_id);
 		gb_connection_hd_cport_id_free(connection);
-		gb_protocol_put(connection);
+		gb_protocol_put(connection->protocol);
 		put_device(&connection->dev);
 		return NULL;
 	}
@@ -239,8 +239,7 @@ void gb_connection_destroy(struct gb_connection *connection)
 	spin_unlock_irq(&gb_connections_lock);
 
 	gb_connection_hd_cport_id_free(connection);
-	/* kref_put(connection->hd); */
-	gb_protocol_put(connection);
+	gb_protocol_put(connection->protocol);
 
 	device_del(&connection->dev);
 }

drivers/staging/greybus/connection.h

@@ -41,7 +41,6 @@ struct gb_connection {
 	struct list_head		interface_links;
 
 	struct gb_protocol		*protocol;
-	struct list_head		protocol_links;
 
 	enum gb_connection_state	state;
 

drivers/staging/greybus/protocol.c

@@ -24,18 +24,6 @@ static struct gb_protocol *_gb_protocol_find(u8 id, u8 major, u8 minor)
 	return NULL;
 }
 
-/* This is basically for debug */
-static struct gb_protocol *gb_protocol_find(u8 id, u8 major, u8 minor)
-{
-	struct gb_protocol *protocol;
-
-	spin_lock_irq(&gb_protocols_lock);
-	protocol = _gb_protocol_find(id, major, minor);
-	spin_unlock_irq(&gb_protocols_lock);
-
-	return protocol;
-}
-
 /* Returns true if protocol was succesfully registered, false otherwise */
 bool gb_protocol_register(u8 id, u8 major, u8 minor)
 {
@@ -49,7 +37,6 @@ bool gb_protocol_register(u8 id, u8 major, u8 minor)
 	protocol->id = id;
 	protocol->major = major;
 	protocol->minor = minor;
-	INIT_LIST_HEAD(&protocol->connections);
 
 	spin_lock_irq(&gb_protocols_lock);
 	existing = _gb_protocol_find(id, major, minor);
@@ -68,64 +55,64 @@ bool gb_protocol_register(u8 id, u8 major, u8 minor)
 /* Returns true if successful, false otherwise */
 bool gb_protocol_deregister(struct gb_protocol *protocol)
 {
+	u8 protocol_count;
+
 	spin_lock_irq(&gb_protocols_lock);
-	if (list_empty(&protocol->connections))
+	protocol = _gb_protocol_find(protocol->id, protocol->major,
+						protocol->minor);
+	if (protocol) {
+		protocol_count = protocol->count;
+		if (!protocol_count)
 			list_del(&protocol->links);
-	else
-		protocol = NULL;	/* Protocol is still in use */
+	}
 	spin_unlock_irq(&gb_protocols_lock);
 	kfree(protocol);
 
-	return protocol != NULL;
+	return protocol && !protocol_count;
 }
 
-/* Returns true if successful, false otherwise */
-bool
-gb_protocol_get(struct gb_connection *connection, u8 id, u8 major, u8 minor)
+/* Returns the requested protocol if available, or a null pointer */
+struct gb_protocol *gb_protocol_get(u8 id, u8 major, u8 minor)
 {
 	struct gb_protocol *protocol;
-
-	/* Sanity */
-	if (!list_empty(&connection->protocol_links) ||
-			!connection->protocol->id) {
-		gb_connection_err(connection,
-			"connection already has protocol");
-		return false;
-	}
+	u8 protocol_count;
 
 	spin_lock_irq(&gb_protocols_lock);
 	protocol = _gb_protocol_find(id, major, minor);
-	if (protocol)
-		list_add(&connection->protocol_links, &protocol->connections);
+	if (protocol) {
+		protocol_count = protocol->count;
+		if (protocol_count != U8_MAX)
+			protocol->count++;
+	}
 	spin_unlock_irq(&gb_protocols_lock);
-	connection->protocol = protocol;
 
-	return protocol != NULL;
+	if (protocol)
+		WARN_ON(protocol_count == U8_MAX);
+	else
+		pr_err("protocol id %hhu version %hhu.%hhu not found\n",
+			id, major, minor);
+
+	return protocol;
 }
 
-void gb_protocol_put(struct gb_connection *connection)
+void gb_protocol_put(struct gb_protocol *protocol)
 {
-	struct gb_protocol *protocol = connection->protocol;
 	u8 major = protocol->major;
 	u8 minor = protocol->minor;
-
-	/* Sanity checks */
-	if (list_empty(&connection->protocol_links)) {
-		gb_connection_err(connection,
-			"connection protocol not recorded");
-		return;
-	}
-	if (!protocol) {
-		gb_connection_err(connection, "connection has no protocol");
-		return;
-	}
-	if (gb_protocol_find(protocol->id, major, minor) != protocol)  {
-		gb_connection_err(connection, "connection protocol not found");
-		return;
-	}
+	u8 protocol_count;
 
 	spin_lock_irq(&gb_protocols_lock);
-	list_del(&connection->protocol_links);
-	connection->protocol = NULL;
+	protocol = _gb_protocol_find(protocol->id, protocol->major,
+						protocol->minor);
+	if (protocol) {
+		protocol_count = protocol->count;
+		if (protocol_count)
+			protocol->count--;
+	}
 	spin_unlock_irq(&gb_protocols_lock);
+	if (protocol)
+		WARN_ON(!protocol_count);
+	else
+		pr_err("protocol id %hhu version %hhu.%hhu not found\n",
+			protocol->id, major, minor);
 }

drivers/staging/greybus/protocol.h

@@ -20,16 +20,15 @@ struct gb_protocol {
 	u8			id;
 	u8			major;
 	u8			minor;
+	u8			count;
 
-	struct list_head	connections;	/* protocol users */
 	struct list_head	links;		/* global list */
 };
 
 bool gb_protocol_register(u8 id, u8 major, u8 minor);
 bool gb_protocol_deregister(struct gb_protocol *protocol);
 
-bool gb_protocol_get(struct gb_connection *connection, u8 id,
-				u8 major, u8 minor);
-void gb_protocol_put(struct gb_connection *connection);
+struct gb_protocol *gb_protocol_get(u8 id, u8 major, u8 minor);
+void gb_protocol_put(struct gb_protocol *protocol);
 
 #endif /* __PROTOCOL_H */