diff --git a/drivers/isdn/gigaset/capi.c b/drivers/isdn/gigaset/capi.c
index 964a55fb1486..ac4cfeed3946 100644
--- a/drivers/isdn/gigaset/capi.c
+++ b/drivers/isdn/gigaset/capi.c
@@ -169,17 +169,6 @@ static inline void ignore_cstruct_param(struct cardstate *cs, _cstruct param,
 			 msgname, paramname);
 }
 
-/*
- * convert hex to binary
- */
-static inline u8 hex2bin(char c)
-{
-	int result = c & 0x0f;
-	if (c & 0x40)
-		result += 9;
-	return result;
-}
-
 /*
  * convert an IE from Gigaset hex string to ETSI binary representation
  * including length byte
@@ -191,7 +180,7 @@ static int encode_ie(char *in, u8 *out, int maxlen)
 	while (*in) {
 		if (!isxdigit(in[0]) || !isxdigit(in[1]) || l >= maxlen)
 			return -1;
-		out[++l] = (hex2bin(in[0]) << 4) + hex2bin(in[1]);
+		out[++l] = (hex_to_bin(in[0]) << 4) + hex_to_bin(in[1]);
 		in += 2;
 	}
 	out[0] = l;