Linux 3.5 will have get_ts_info to support the Precision Time Protocol.

http://linuxptp.sourceforge.net/
http://en.wikipedia.org/wiki/Precision_Time_Protocol

We cannot backport this support given that this introduces
a data structure change on the ethtool_ops.

commit c8f3a8c31069137fe0100e6920558f1a7487ef3c
Author: Richard Cochran <richardcochran@gmail.com>
Date:   Tue Apr 3 22:59:17 2012 +0000

    ethtool: Introduce a method for getting time stamping capabilities.
    
    This commit adds a new ethtool ioctl that exposes the SO_TIMESTAMPING
    capabilities of a network interface. In addition, user space programs
    can use this ioctl to discover the PTP Hardware Clock (PHC) device
    associated with the interface.
    
    Since software receive time stamps are handled by the stack, the generic
    ethtool code can answer the query correctly in case the MAC or PHY
    drivers lack special time stamping features.
    
    Signed-off-by: Richard Cochran <richardcochran@gmail.com>
    Reviewed-by: Ben Hutchings <bhutchings@solarflare.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -911,7 +911,9 @@ static const struct ethtool_ops usbnet_e
 	.get_drvinfo		= usbnet_get_drvinfo,
 	.get_msglevel		= usbnet_get_msglevel,
 	.set_msglevel		= usbnet_set_msglevel,
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,5,0))
 	.get_ts_info		= ethtool_op_get_ts_info,
+#endif
 };
 
 /*-------------------------------------------------------------------------*/
