[PATCH v3 2/3] net: ethtool: add KSZ87xx low-loss PHY tunable

[Fidelio Lawson]

Introduce a new PHY tunable identifier,
ETHTOOL_PHY_KSZ87XX_LOW_LOSS, to allow userspace to control the
KSZ87xx low-loss cable erratum through the ethtool PHY tunable
interface.

KSZ87xx switches integrate embedded PHYs whose receiver behavior may
require specific equalizer or low-pass filter adjustments when used
with short or low-loss Ethernet cables, as described in Microchip
errata DS80000687C (Module 3). The new tunable provides a userspace
interface for selecting the desired operating mode.

The tunable uses a u8 value and is vendor-specific by design. The
actual handling is implemented by the corresponding PHY driver.

Signed-off-by: Fidelio Lawson <fidelio.lawson@xxxxxxxxxx>
---
 include/uapi/linux/ethtool.h | 1 +
 net/ethtool/common.c         | 1 +
 net/ethtool/ioctl.c          | 1 +
 3 files changed, 3 insertions(+)

diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index b74b80508553..5c539e1bca4b 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h
@@ -295,6 +295,7 @@ enum phy_tunable_id {
 	 * Add your fresh new phy tunable attribute above and remember to update
 	 * phy_tunable_strings[] in net/ethtool/common.c
 	 */
+	ETHTOOL_PHY_KSZ87XX_LOW_LOSS,
 	__ETHTOOL_PHY_TUNABLE_COUNT,
 };
 
diff --git a/net/ethtool/common.c b/net/ethtool/common.c
index e252cf20c22f..e1c98ce66093 100644
--- a/net/ethtool/common.c
+++ b/net/ethtool/common.c
@@ -101,6 +101,7 @@ phy_tunable_strings[__ETHTOOL_PHY_TUNABLE_COUNT][ETH_GSTRING_LEN] = {
 	[ETHTOOL_PHY_DOWNSHIFT]	= "phy-downshift",
 	[ETHTOOL_PHY_FAST_LINK_DOWN] = "phy-fast-link-down",
 	[ETHTOOL_PHY_EDPD]	= "phy-energy-detect-power-down",
+	[ETHTOOL_PHY_KSZ87XX_LOW_LOSS] = "phy-ksz87xx-low-loss",
 };
 
 #define __LINK_MODE_NAME(speed, type, duplex) \
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index ff4b4780d6af..9e7bd887acf5 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -3109,6 +3109,7 @@ static int ethtool_phy_tunable_valid(const struct ethtool_tunable *tuna)
 	switch (tuna->id) {
 	case ETHTOOL_PHY_DOWNSHIFT:
 	case ETHTOOL_PHY_FAST_LINK_DOWN:
+	case ETHTOOL_PHY_KSZ87XX_LOW_LOSS:
 		if (tuna->len != sizeof(u8) ||
 		    tuna->type_id != ETHTOOL_TUNABLE_U8)
 			return -EINVAL;

-- 
2.53.0