[PATCH] netdevice.h add netif_msg_init helper

This patch adds a helper function to initialize the debug bit mask
for use with netif_msg_*.  When the debug_value is out of range
it returns the default_msg_enable_bits.  Tested IA32.

include/linux/netdevice.h

@@ -774,6 +774,17 @@ enum {
 #define netif_msg_hw(p)		((p)->msg_enable & NETIF_MSG_HW)
 #define netif_msg_wol(p)	((p)->msg_enable & NETIF_MSG_WOL)
 
+static inline u32 netif_msg_init(int debug_value, int default_msg_enable_bits)
+{
+	/* use default */
+	if (debug_value < 0 || debug_value >= (sizeof(u32) * 8))
+		return default_msg_enable_bits;
+	if (debug_value == 0)	/* no output */
+		return 0;
+	/* set low N bits */
+	return (1 << debug_value) - 1;
+}
+
 /* Schedule rx intr now? */
 
 static inline int netif_rx_schedule_prep(struct net_device *dev)