diff --git a/ddbridge/ddbridge-core.c b/ddbridge/ddbridge-core.c
index bfbd7c1..06010b9 100644
--- a/ddbridge/ddbridge-core.c
+++ b/ddbridge/ddbridge-core.c
@@ -30,7 +30,7 @@
 
 struct workqueue_struct *ddb_wq;
 
-DEFINE_MUTEX(redirect_lock); /* lock for redirect */
+static DEFINE_MUTEX(redirect_lock); /* lock for redirect */
 
 static int adapter_alloc;
 module_param(adapter_alloc, int, 0444);
@@ -157,8 +157,8 @@ static void ddb_redirect_dma(struct ddb *dev,
 
 static int ddb_unredirect(struct ddb_port *port)
 {
-	struct ddb_input *oredi, *iredi = 0;
-	struct ddb_output *iredo = 0;
+	struct ddb_input *oredi, *iredi = NULL;
+	struct ddb_output *iredo = NULL;
 
 	mutex_lock(&redirect_lock);
 	if (port->output->dma->running) {
@@ -179,14 +179,14 @@ static int ddb_unredirect(struct ddb_port *port)
 				ddb_redirect_dma(oredi->port->dev,
 						 oredi->dma, iredo->dma);
 			}
-			port->input[0]->redo = 0;
+			port->input[0]->redo = NULL;
 			ddb_set_dma_table(port->input[0]);
 		}
 		oredi->redi = iredi;
-		port->input[0]->redi = 0;
+		port->input[0]->redi = NULL;
 	}
-	oredi->redo = 0;
-	port->output->redi = 0;
+	oredi->redo = NULL;
+	port->output->redi = NULL;
 
 	ddb_set_dma_table(oredi);
 done:
@@ -228,7 +228,7 @@ static int ddb_redirect(u32 i, u32 p)
 	if (input2) {
 		if (input->redi) {
 			input2->redi = input->redi;
-			input->redi = 0;
+			input->redi = NULL;
 		} else {
 			input2->redi = input;
 		}
@@ -1005,11 +1005,11 @@ static const struct file_operations ci_fops = {
 	.open    = ts_open,
 	.release = ts_release,
 	.poll    = ts_poll,
-	.mmap    = 0,
+	.mmap    = NULL,
 };
 
 static struct dvb_device dvbdev_ci = {
-	.priv    = 0,
+	.priv    = NULL,
 	.readers = 1,
 	.writers = 1,
 	.users   = 2,
@@ -1032,12 +1032,12 @@ static const struct file_operations mod_fops = {
 	.open    = mod_open,
 	.release = mod_release,
 	.poll    = ts_poll,
-	.mmap    = 0,
+	.mmap    = NULL,
 	.unlocked_ioctl = mod_ioctl,
 };
 
 static struct dvb_device dvbdev_mod = {
-	.priv    = 0,
+	.priv    = NULL,
 	.readers = 1,
 	.writers = 1,
 	.users   = 2,
@@ -4156,7 +4156,7 @@ static int ddb_device_create(struct ddb *dev)
 	if (res) {
 		ddb_device_attrs_del(dev);
 		device_destroy(&ddb_class, MKDEV(ddb_major, dev->nr));
-		ddbs[dev->nr] = 0;
+		ddbs[dev->nr] = NULL;
 		dev->ddb_dev = ERR_PTR(-ENODEV);
 	} else {
 		ddb_num++;