igb: implement SIOCGHWTSTAMP ioctl

This patch adds support for the SIOCGHWTSTAMP ioctl which enables user
processes to read the current hwtstamp_config settings
non-destructively. Previously a process had to be privileged and could
only set values, it couldn't return what is currently set without
possibly overwriting the value.

This patch adds support for this new operation into igb by keeping a
shadow copy of the config in the adapter structure, which is returned
upon request.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Matthew Vick <matthew.vick@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
index a202c96..411b213 100644
--- a/drivers/net/ethernet/intel/igb/igb.h
+++ b/drivers/net/ethernet/intel/igb/igb.h
@@ -434,6 +434,7 @@
 	struct delayed_work ptp_overflow_work;
 	struct work_struct ptp_tx_work;
 	struct sk_buff *ptp_tx_skb;
+	struct hwtstamp_config tstamp_config;
 	unsigned long ptp_tx_start;
 	unsigned long last_rx_ptp_check;
 	spinlock_t tmreg_lock;
@@ -545,8 +546,8 @@
 	rx_ring->last_rx_timestamp = jiffies;
 }
 
-int igb_ptp_hwtstamp_ioctl(struct net_device *netdev, struct ifreq *ifr,
-			   int cmd);
+int igb_ptp_set_ts_config(struct net_device *netdev, struct ifreq *ifr);
+int igb_ptp_get_ts_config(struct net_device *netdev, struct ifreq *ifr);
 #ifdef CONFIG_IGB_HWMON
 void igb_sysfs_exit(struct igb_adapter *adapter);
 int igb_sysfs_init(struct igb_adapter *adapter);