If hardware support the frame preemption, driver could set the
ethernet device with hw_features and features with NETIF_F_PREEMPTION
when initializing the port driver.

User can check the feature 'tx-preemption' by command 'ethtool -k
devname'. If hareware set preemption feature. The property would
be a fixed value 'on' if hardware support the frame preemption.
Feature would show a fixed value 'off' if hardware don't support
the frame preemption.

Command 'ethtool devname' and 'ethtool -s devname preemption N'
would show/set which traffic classes are frame preemptable.

Port driver would implement the frame preemption in the function
get_link_ksettings() and set_link_ksettings() in the struct ethtool_ops.

Signed-off-by: Po Liu <redacted>
---
 include/linux/netdev_features.h | 5 ++++-
 include/uapi/linux/ethtool.h    | 5 ++++-
 net/core/ethtool.c              | 1 +
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
index 4b19c544c59a..299750a8b414 100644
--- a/include/linux/netdev_features.h
+++ b/include/linux/netdev_features.h

@@ -80,6 +80,7 @@ enum {
 
 	NETIF_F_GRO_HW_BIT,		/* Hardware Generic receive offload */
 	NETIF_F_HW_TLS_RECORD_BIT,	/* Offload TLS record */
+	NETIF_F_HW_PREEMPTION_BIT,	/* Hardware TC frame preemption */
 
 	/*
 	 * Add your fresh new feature above and remember to update

@@ -150,6 +151,7 @@ enum {
 #define NETIF_F_GSO_UDP_L4	__NETIF_F(GSO_UDP_L4)
 #define NETIF_F_HW_TLS_TX	__NETIF_F(HW_TLS_TX)
 #define NETIF_F_HW_TLS_RX	__NETIF_F(HW_TLS_RX)
+#define NETIF_F_PREEMPTION	__NETIF_F(HW_PREEMPTION)
 
 /* Finds the next feature with the highest number of the range of start till 0.
  */

@@ -175,7 +177,8 @@ static inline int find_next_netdev_feature(u64 feature, unsigned long start)
 /* Features valid for ethtool to change */
 /* = all defined minus driver/device-class-related */
 #define NETIF_F_NEVER_CHANGE	(NETIF_F_VLAN_CHALLENGED | \
-				 NETIF_F_LLTX | NETIF_F_NETNS_LOCAL)
+				 NETIF_F_LLTX | NETIF_F_NETNS_LOCAL | \
+				 NETIF_F_PREEMPTION)
 
 /* remember that ((t)1 << t_BITS) is undefined in C99 */
 #define NETIF_F_ETHTOOL_BITS	((__NETIF_F_BIT(NETDEV_FEATURE_COUNT - 1) | \

diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index d4591792f0b4..12ffb34afbfa 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h

@@ -1776,6 +1776,8 @@ enum ethtool_reset_flags {
 };
 #define ETH_RESET_SHARED_SHIFT	16
 
+/* Disable preemtion. */
+#define PREEMPTION_DISABLE     0x0
 
 /**
  * struct ethtool_link_settings - link control and status

@@ -1886,7 +1888,8 @@ struct ethtool_link_settings {
 	__s8	link_mode_masks_nwords;
 	__u8	transceiver;
 	__u8	reserved1[3];
-	__u32	reserved[7];
+	__u32	preemption;
+	__u32	reserved[6];
 	__u32	link_mode_masks[0];
 	/* layout of link_mode_masks fields:
 	 * __u32 map_supported[link_mode_masks_nwords];

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index cd9bc67381b2..6ffcd8a602b8 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c

@@ -111,6 +111,7 @@ static const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN]
 	[NETIF_F_HW_TLS_RECORD_BIT] =	"tls-hw-record",
 	[NETIF_F_HW_TLS_TX_BIT] =	 "tls-hw-tx-offload",
 	[NETIF_F_HW_TLS_RX_BIT] =	 "tls-hw-rx-offload",
+	[NETIF_F_HW_PREEMPTION_BIT] =	 "tx-preemption",
 };
 
 static const char

-- 
2.17.1