HSI: export method to (un)register clients

Expose method for registering and unregistering HSI clients, so that
client drivers can register other client drivers.

This is useful for HSI drivers, which want to use the functionality
of other HSI drivers. For example the N900 modem driver can load HSI
drivers for mcsaab protocol and speech protocol.

Signed-off-by: Sebastian Reichel <sre@kernel.org>
Reviewed-by: Pavel Machek <pavel@ucw.cz>
Tested-By: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
diff --git a/drivers/hsi/hsi.c b/drivers/hsi/hsi.c
index de2ad8f..834a2d6 100644
--- a/drivers/hsi/hsi.c
+++ b/drivers/hsi/hsi.c
@@ -69,14 +69,15 @@
 	kfree(cl);
 }
 
-static void hsi_new_client(struct hsi_port *port, struct hsi_board_info *info)
+struct hsi_client *hsi_new_client(struct hsi_port *port,
+						struct hsi_board_info *info)
 {
 	struct hsi_client *cl;
 	size_t size;
 
 	cl = kzalloc(sizeof(*cl), GFP_KERNEL);
 	if (!cl)
-		return;
+		return NULL;
 
 	cl->tx_cfg = info->tx_cfg;
 	if (cl->tx_cfg.channels) {
@@ -103,7 +104,10 @@
 		pr_err("hsi: failed to register client: %s\n", info->name);
 		put_device(&cl->device);
 	}
+
+	return cl;
 }
+EXPORT_SYMBOL_GPL(hsi_new_client);
 
 static void hsi_scan_board_info(struct hsi_controller *hsi)
 {
@@ -119,12 +123,13 @@
 		}
 }
 
-static int hsi_remove_client(struct device *dev, void *data __maybe_unused)
+int hsi_remove_client(struct device *dev, void *data __maybe_unused)
 {
 	device_unregister(dev);
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(hsi_remove_client);
 
 static int hsi_remove_port(struct device *dev, void *data __maybe_unused)
 {