protocol: Add 'get_latest' supported protocol

Change the implementation of finding the protocol driver - which looks
for a hardcoded 0,1 major/minor initiated in connection_create - to
finding the highest supported major,minor version overall, or one that
matches the requested major version.

This is the initial re-design of the version negotiation that allows us
to correctly send the currently implemented protocol driver version.

Change-Id: I8f5aa67a92622d69b6f469920fe1d9cd15e56c6e
Signed-off-by: Jason Hrycay <jason.hrycay@motorola.com>
Reviewed-on: http://gerrit.mot.com/841249
SLTApproved: Slta Waiver <sltawvr@motorola.com>
SME-Granted: SME Approvals Granted
Reviewed-by: Gregory Meiste <w30289@motorola.com>

connection.c

@@ -550,14 +550,11 @@ static int gb_connection_bind_protocol(struct gb_connection *connection)
 {
 	struct gb_protocol *protocol;
 
-	protocol = gb_protocol_get(connection->protocol_id,
-				   connection->major,
-				   connection->minor);
+	protocol = gb_protocol_get_latest(connection->protocol_id, 0, false);
 	if (!protocol) {
 		dev_err(&connection->hd->dev,
-				"protocol 0x%02x version %u.%u not found\n",
-				connection->protocol_id,
-				connection->major, connection->minor);
+				"protocol 0x%02x not found\n",
+				connection->protocol_id);
 		return -EPROTONOSUPPORT;
 	}
 	connection->protocol = protocol;

protocol.c

@@ -41,6 +41,30 @@ static struct gb_protocol *gb_protocol_find(u8 id, u8 major, u8 minor)
 	return NULL;
 }
 
+/* Caller must hold gb_protocols_lock */
+static struct gb_protocol *gb_protocol_find_latest(u8 id, u8 major, bool match)
+{
+	struct gb_protocol *protocol;
+
+	list_for_each_entry(protocol, &gb_protocols, links) {
+		if (protocol->id < id)
+			continue;
+		if (protocol->id > id)
+			break;
+
+		if (!match)
+			return protocol;
+
+		if (protocol->major > major)
+			continue;
+		if (protocol->major < major)
+			break;
+
+		return protocol;
+	}
+	return NULL;
+}
+
 int __gb_protocol_register(struct gb_protocol *protocol, struct module *module)
 {
 	struct gb_protocol *existing;
@@ -142,6 +166,31 @@ struct gb_protocol *gb_protocol_get(u8 id, u8 major, u8 minor)
 	return protocol;
 }
 
+/* Returns the latest protocol version supported, or null pointer */
+struct gb_protocol *gb_protocol_get_latest(u8 id, u8 major, bool match)
+{
+	struct gb_protocol *protocol;
+	u8 protocol_count;
+
+	spin_lock_irq(&gb_protocols_lock);
+	protocol = gb_protocol_find_latest(id, major, match);
+	if (protocol) {
+		if (!try_module_get(protocol->owner)) {
+			protocol = NULL;
+		} else {
+			protocol_count = protocol->count;
+			if (protocol_count != U8_MAX)
+				protocol->count++;
+		}
+	}
+	spin_unlock_irq(&gb_protocols_lock);
+
+	if (protocol)
+		WARN_ON(protocol_count == U8_MAX);
+
+	return protocol;
+}
+
 int gb_protocol_get_version(struct gb_connection *connection)
 {
 	struct gb_protocol_version_request request;

protocol.h

@@ -50,6 +50,7 @@ void gb_protocol_deregister(struct gb_protocol *protocol);
 	__gb_protocol_register(protocol, THIS_MODULE)
 
 struct gb_protocol *gb_protocol_get(u8 id, u8 major, u8 minor);
+struct gb_protocol *gb_protocol_get_latest(u8 id, u8 major, bool match);
 int gb_protocol_get_version(struct gb_connection *connection);
 
 void gb_protocol_put(struct gb_protocol *protocol);