ethtool: add support to set/get tx copybreak buf size via ethtool

Add support for ethtool to set/get tx copybreak buf size.

Signed-off-by: Hao Chen <[e-mail]>
Signed-off-by: Guangbin Huang <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/uapi/linux/ethtool.h

···
 	ETHTOOL_RX_COPYBREAK,
 	ETHTOOL_TX_COPYBREAK,
 	ETHTOOL_PFC_PREVENTION_TOUT, /* timeout in msecs */
+	ETHTOOL_TX_COPYBREAK_BUF_SIZE,
 	/*
 	 * Add your fresh new tunable attribute above and remember to update
 	 * tunable_strings[] in net/ethtool/common.c

net/ethtool/common.c

···
 	[ETHTOOL_RX_COPYBREAK]	= "rx-copybreak",
 	[ETHTOOL_TX_COPYBREAK]	= "tx-copybreak",
 	[ETHTOOL_PFC_PREVENTION_TOUT] = "pfc-prevention-tout",
+	[ETHTOOL_TX_COPYBREAK_BUF_SIZE] = "tx-copybreak-buf-size",
 };
 
 const char

net/ethtool/ioctl.c

···
 	switch (tuna->id) {
 	case ETHTOOL_RX_COPYBREAK:
 	case ETHTOOL_TX_COPYBREAK:
+	case ETHTOOL_TX_COPYBREAK_BUF_SIZE:
 		if (tuna->len != sizeof(u32) ||
 		    tuna->type_id != ETHTOOL_TUNABLE_U32)
 			return -EINVAL;