diff --git a/drivers/isdn/hardware/avm/b1.c b/drivers/isdn/hardware/avm/b1.c
index 4484a64..abf05ec 100644
--- a/drivers/isdn/hardware/avm/b1.c
+++ b/drivers/isdn/hardware/avm/b1.c
@@ -661,11 +661,11 @@
 	len += sprintf(page+len, "%-16s %s\n", "type", s);
 	if (card->cardtype == avm_t1isa)
 	   len += sprintf(page+len, "%-16s %d\n", "cardnr", card->cardnr);
-	if ((s = cinfo->version[VER_DRIVER]) != 0)
+	if ((s = cinfo->version[VER_DRIVER]) != NULL)
 	   len += sprintf(page+len, "%-16s %s\n", "ver_driver", s);
-	if ((s = cinfo->version[VER_CARDTYPE]) != 0)
+	if ((s = cinfo->version[VER_CARDTYPE]) != NULL)
 	   len += sprintf(page+len, "%-16s %s\n", "ver_cardtype", s);
-	if ((s = cinfo->version[VER_SERIAL]) != 0)
+	if ((s = cinfo->version[VER_SERIAL]) != NULL)
 	   len += sprintf(page+len, "%-16s %s\n", "ver_serial", s);
 
 	if (card->cardtype != avm_m1) {
@@ -788,9 +788,9 @@
 	char *p;
 	char rev[32];
 
-	if ((p = strchr(revision, ':')) != 0 && p[1]) {
+	if ((p = strchr(revision, ':')) != NULL && p[1]) {
 		strlcpy(rev, p + 2, 32);
-		if ((p = strchr(rev, '$')) != 0 && p > rev)
+		if ((p = strchr(rev, '$')) != NULL && p > rev)
 		   *(p-1) = 0;
 	} else
 		strcpy(rev, "1.0");
diff --git a/drivers/isdn/hardware/avm/b1dma.c b/drivers/isdn/hardware/avm/b1dma.c
index 669f6f6..da34b98 100644
--- a/drivers/isdn/hardware/avm/b1dma.c
+++ b/drivers/isdn/hardware/avm/b1dma.c
@@ -883,11 +883,11 @@
 	default: s = "???"; break;
 	}
 	len += sprintf(page+len, "%-16s %s\n", "type", s);
-	if ((s = cinfo->version[VER_DRIVER]) != 0)
+	if ((s = cinfo->version[VER_DRIVER]) != NULL)
 	   len += sprintf(page+len, "%-16s %s\n", "ver_driver", s);
-	if ((s = cinfo->version[VER_CARDTYPE]) != 0)
+	if ((s = cinfo->version[VER_CARDTYPE]) != NULL)
 	   len += sprintf(page+len, "%-16s %s\n", "ver_cardtype", s);
-	if ((s = cinfo->version[VER_SERIAL]) != 0)
+	if ((s = cinfo->version[VER_SERIAL]) != NULL)
 	   len += sprintf(page+len, "%-16s %s\n", "ver_serial", s);
 
 	if (card->cardtype != avm_m1) {
@@ -970,9 +970,9 @@
 	char *p;
 	char rev[32];
 
-	if ((p = strchr(revision, ':')) != 0 && p[1]) {
+	if ((p = strchr(revision, ':')) != NULL && p[1]) {
 		strlcpy(rev, p + 2, sizeof(rev));
-		if ((p = strchr(rev, '$')) != 0 && p > rev)
+		if ((p = strchr(rev, '$')) != NULL && p > rev)
 		   *(p-1) = 0;
 	} else
 		strcpy(rev, "1.0");
diff --git a/drivers/isdn/hardware/avm/b1isa.c b/drivers/isdn/hardware/avm/b1isa.c
index 80fb488..1e288ee 100644
--- a/drivers/isdn/hardware/avm/b1isa.c
+++ b/drivers/isdn/hardware/avm/b1isa.c
@@ -203,9 +203,9 @@
 	char rev[32];
 	int i;
 
-	if ((p = strchr(revision, ':')) != 0 && p[1]) {
+	if ((p = strchr(revision, ':')) != NULL && p[1]) {
 		strlcpy(rev, p + 2, 32);
-		if ((p = strchr(rev, '$')) != 0 && p > rev)
+		if ((p = strchr(rev, '$')) != NULL && p > rev)
 		   *(p-1) = 0;
 	} else
 		strcpy(rev, "1.0");
diff --git a/drivers/isdn/hardware/avm/b1pci.c b/drivers/isdn/hardware/avm/b1pci.c
index 90e2e66..5b314a2 100644
--- a/drivers/isdn/hardware/avm/b1pci.c
+++ b/drivers/isdn/hardware/avm/b1pci.c
@@ -382,9 +382,9 @@
 	char rev[32];
 	int err;
 
-	if ((p = strchr(revision, ':')) != 0 && p[1]) {
+	if ((p = strchr(revision, ':')) != NULL && p[1]) {
 		strlcpy(rev, p + 2, 32);
-		if ((p = strchr(rev, '$')) != 0 && p > rev)
+		if ((p = strchr(rev, '$')) != NULL && p > rev)
 		   *(p-1) = 0;
 	} else
 		strcpy(rev, "1.0");
diff --git a/drivers/isdn/hardware/avm/b1pcmcia.c b/drivers/isdn/hardware/avm/b1pcmcia.c
index e479c0a..7740403 100644
--- a/drivers/isdn/hardware/avm/b1pcmcia.c
+++ b/drivers/isdn/hardware/avm/b1pcmcia.c
@@ -201,9 +201,9 @@
 	char *p;
 	char rev[32];
 
-	if ((p = strchr(revision, ':')) != 0 && p[1]) {
+	if ((p = strchr(revision, ':')) != NULL && p[1]) {
 		strlcpy(rev, p + 2, 32);
-		if ((p = strchr(rev, '$')) != 0 && p > rev)
+		if ((p = strchr(rev, '$')) != NULL && p > rev)
 		   *(p-1) = 0;
 	} else
 		strcpy(rev, "1.0");
diff --git a/drivers/isdn/hardware/avm/c4.c b/drivers/isdn/hardware/avm/c4.c
index 4bbbbe6..9df1d3f 100644
--- a/drivers/isdn/hardware/avm/c4.c
+++ b/drivers/isdn/hardware/avm/c4.c
@@ -1088,11 +1088,11 @@
 	default: s = "???"; break;
 	}
 	len += sprintf(page+len, "%-16s %s\n", "type", s);
-	if ((s = cinfo->version[VER_DRIVER]) != 0)
+	if ((s = cinfo->version[VER_DRIVER]) != NULL)
 	   len += sprintf(page+len, "%-16s %s\n", "ver_driver", s);
-	if ((s = cinfo->version[VER_CARDTYPE]) != 0)
+	if ((s = cinfo->version[VER_CARDTYPE]) != NULL)
 	   len += sprintf(page+len, "%-16s %s\n", "ver_cardtype", s);
-	if ((s = cinfo->version[VER_SERIAL]) != 0)
+	if ((s = cinfo->version[VER_SERIAL]) != NULL)
 	   len += sprintf(page+len, "%-16s %s\n", "ver_serial", s);
 
 	if (card->cardtype != avm_m1) {
@@ -1167,7 +1167,7 @@
 	}
 
 	card->mbase = ioremap(card->membase, 128);
-	if (card->mbase == 0) {
+	if (card->mbase == NULL) {
 		printk(KERN_NOTICE "c4: can't remap memory at 0x%lx\n",
 		       card->membase);
 		retval = -EIO;
@@ -1291,9 +1291,9 @@
 	char rev[32];
 	int err;
 
-	if ((p = strchr(revision, ':')) != 0 && p[1]) {
+	if ((p = strchr(revision, ':')) != NULL && p[1]) {
 		strlcpy(rev, p + 2, 32);
-		if ((p = strchr(rev, '$')) != 0 && p > rev)
+		if ((p = strchr(rev, '$')) != NULL && p > rev)
 		   *(p-1) = 0;
 	} else
 		strcpy(rev, "1.0");
diff --git a/drivers/isdn/hardware/avm/t1isa.c b/drivers/isdn/hardware/avm/t1isa.c
index 6130724..e772449 100644
--- a/drivers/isdn/hardware/avm/t1isa.c
+++ b/drivers/isdn/hardware/avm/t1isa.c
@@ -551,9 +551,9 @@
 	char *p;
 	int i;
 
-	if ((p = strchr(revision, ':')) != 0 && p[1]) {
+	if ((p = strchr(revision, ':')) != NULL && p[1]) {
 		strlcpy(rev, p + 2, 32);
-		if ((p = strchr(rev, '$')) != 0 && p > rev)
+		if ((p = strchr(rev, '$')) != NULL && p > rev)
 		   *(p-1) = 0;
 	} else
 		strcpy(rev, "1.0");
diff --git a/drivers/isdn/hardware/avm/t1pci.c b/drivers/isdn/hardware/avm/t1pci.c
index d1e253c..e6d298d 100644
--- a/drivers/isdn/hardware/avm/t1pci.c
+++ b/drivers/isdn/hardware/avm/t1pci.c
@@ -233,9 +233,9 @@
 	char rev[32];
 	int err;
 
-	if ((p = strchr(revision, ':')) != 0 && p[1]) {
+	if ((p = strchr(revision, ':')) != NULL && p[1]) {
 		strlcpy(rev, p + 2, 32);
-		if ((p = strchr(rev, '$')) != 0 && p > rev)
+		if ((p = strchr(rev, '$')) != NULL && p > rev)
 		   *(p-1) = 0;
 	} else
 		strcpy(rev, "1.0");