ethtool: netlink: add ETHTOOL_MSG_MSE_GET and wire up PHY MSE access

Introduce the userspace entry point for PHY MSE diagnostics via
ethtool netlink. This exposes the core API added previously and
returns both capability information and one or more snapshots.

Userspace sends ETHTOOL_MSG_MSE_GET. The reply carries:
- ETHTOOL_A_MSE_CAPABILITIES: scale limits and timing information
- ETHTOOL_A_MSE_CHANNEL_* nests: one or more snapshots (per-channel
  if available, otherwise WORST, otherwise LINK)

Link down returns -ENETDOWN.

Changes:
  - YAML: add attribute sets (mse, mse-capabilities, mse-snapshot)
    and the mse-get operation
  - UAPI (generated): add ETHTOOL_A_MSE_* enums and message IDs,
    ETHTOOL_MSG_MSE_GET/REPLY
  - ethtool core: add net/ethtool/mse.c implementing the request,
    register genl op, and hook into ethnl dispatch
  - docs: document MSE_GET in ethtool-netlink.rst

The include/uapi/linux/ethtool_netlink_generated.h is generated
from Documentation/netlink/specs/ethtool.yaml.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://patch.msgid.link/20251027122801.982364-3-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

4 files changed, 342 insertions, 1 deletions

diff --git a/net/ethtool/Makefile b/net/ethtool/Makefile
index 1e493553b977..629c10916670 100644
--- a/net/ethtool/Makefile
+++ b/net/ethtool/Makefile
@@ -9,4 +9,4 @@ ethtool_nl-y	:= netlink.o bitset.o strset.o linkinfo.o linkmodes.o rss.o \
 		   channels.o coalesce.o pause.o eee.o tsinfo.o cabletest.o \
 		   tunnels.o fec.o eeprom.o stats.o phc_vclocks.o mm.o \
 		   module.o cmis_fw_update.o cmis_cdb.o pse-pd.o plca.o \
-		   phy.o tsconfig.o
+		   phy.o tsconfig.o mse.o
diff --git a/net/ethtool/mse.c b/net/ethtool/mse.c
new file mode 100644
index 000000000000..6aac004c3ffc
--- /dev/null
+++ b/net/ethtool/mse.c
@@ -0,0 +1,329 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/ethtool.h>
+#include <linux/phy.h>
+#include <linux/slab.h>
+
+#include "netlink.h"
+#include "common.h"
+
+/* Channels A-D only; WORST and LINK are exclusive alternatives */
+#define PHY_MSE_CHANNEL_COUNT 4
+
+struct mse_req_info {
+	struct ethnl_req_info base;
+};
+
+struct mse_snapshot_entry {
+	struct phy_mse_snapshot snapshot;
+	int channel;
+};
+
+struct mse_reply_data {
+	struct ethnl_reply_data base;
+	struct phy_mse_capability capability;
+	struct mse_snapshot_entry *snapshots;
+	unsigned int num_snapshots;
+};
+
+static struct mse_reply_data *
+mse_repdata(const struct ethnl_reply_data *reply_base)
+{
+	return container_of(reply_base, struct mse_reply_data, base);
+}
+
+const struct nla_policy ethnl_mse_get_policy[] = {
+	[ETHTOOL_A_MSE_HEADER] = NLA_POLICY_NESTED(ethnl_header_policy_phy),
+};
+
+static int get_snapshot_if_supported(struct phy_device *phydev,
+				     struct mse_reply_data *data,
+				     unsigned int *idx, u32 cap_bit,
+				     enum phy_mse_channel channel)
+{
+	int ret;
+
+	if (data->capability.supported_caps & cap_bit) {
+		ret = phydev->drv->get_mse_snapshot(phydev, channel,
+					&data->snapshots[*idx].snapshot);
+		if (ret)
+			return ret;
+		data->snapshots[*idx].channel = channel;
+		(*idx)++;
+	}
+
+	return 0;
+}
+
+static int mse_get_channels(struct phy_device *phydev,
+			    struct mse_reply_data *data)
+{
+	unsigned int i = 0;
+	int ret;
+
+	if (!data->capability.supported_caps)
+		return 0;
+
+	data->snapshots = kcalloc(PHY_MSE_CHANNEL_COUNT,
+				  sizeof(*data->snapshots), GFP_KERNEL);
+	if (!data->snapshots)
+		return -ENOMEM;
+
+	/* Priority 1: Individual channels */
+	ret = get_snapshot_if_supported(phydev, data, &i, PHY_MSE_CAP_CHANNEL_A,
+					PHY_MSE_CHANNEL_A);
+	if (ret)
+		return ret;
+	ret = get_snapshot_if_supported(phydev, data, &i, PHY_MSE_CAP_CHANNEL_B,
+					PHY_MSE_CHANNEL_B);
+	if (ret)
+		return ret;
+	ret = get_snapshot_if_supported(phydev, data, &i, PHY_MSE_CAP_CHANNEL_C,
+					PHY_MSE_CHANNEL_C);
+	if (ret)
+		return ret;
+	ret = get_snapshot_if_supported(phydev, data, &i, PHY_MSE_CAP_CHANNEL_D,
+					PHY_MSE_CHANNEL_D);
+	if (ret)
+		return ret;
+
+	/* If any individual channels were found, we are done. */
+	if (i > 0) {
+		data->num_snapshots = i;
+		return 0;
+	}
+
+	/* Priority 2: Worst channel, if no individual channels supported. */
+	ret = get_snapshot_if_supported(phydev, data, &i,
+					PHY_MSE_CAP_WORST_CHANNEL,
+					PHY_MSE_CHANNEL_WORST);
+	if (ret)
+		return ret;
+
+	/* If worst channel was found, we are done. */
+	if (i > 0) {
+		data->num_snapshots = i;
+		return 0;
+	}
+
+	/* Priority 3: Link-wide, if nothing else is supported. */
+	ret = get_snapshot_if_supported(phydev, data, &i, PHY_MSE_CAP_LINK,
+					PHY_MSE_CHANNEL_LINK);
+	if (ret)
+		return ret;
+
+	data->num_snapshots = i;
+	return 0;
+}
+
+static int mse_prepare_data(const struct ethnl_req_info *req_base,
+			    struct ethnl_reply_data *reply_base,
+			    const struct genl_info *info)
+{
+	struct mse_reply_data *data = mse_repdata(reply_base);
+	struct net_device *dev = reply_base->dev;
+	struct phy_device *phydev;
+	int ret;
+
+	phydev = ethnl_req_get_phydev(req_base, info->attrs,
+				      ETHTOOL_A_MSE_HEADER, info->extack);
+	if (IS_ERR(phydev))
+		return PTR_ERR(phydev);
+	if (!phydev)
+		return -EOPNOTSUPP;
+
+	ret = ethnl_ops_begin(dev);
+	if (ret)
+		return ret;
+
+	mutex_lock(&phydev->lock);
+
+	if (!phydev->drv || !phydev->drv->get_mse_capability ||
+	    !phydev->drv->get_mse_snapshot) {
+		ret = -EOPNOTSUPP;
+		goto out_unlock;
+	}
+	if (!phydev->link) {
+		ret = -ENETDOWN;
+		goto out_unlock;
+	}
+
+	ret = phydev->drv->get_mse_capability(phydev, &data->capability);
+	if (ret)
+		goto out_unlock;
+
+	ret = mse_get_channels(phydev, data);
+
+out_unlock:
+	mutex_unlock(&phydev->lock);
+	ethnl_ops_complete(dev);
+	if (ret)
+		kfree(data->snapshots);
+	return ret;
+}
+
+static void mse_cleanup_data(struct ethnl_reply_data *reply_base)
+{
+	struct mse_reply_data *data = mse_repdata(reply_base);
+
+	kfree(data->snapshots);
+}
+
+static int mse_reply_size(const struct ethnl_req_info *req_base,
+			  const struct ethnl_reply_data *reply_base)
+{
+	const struct mse_reply_data *data = mse_repdata(reply_base);
+	size_t len = 0;
+	unsigned int i;
+
+	/* ETHTOOL_A_MSE_CAPABILITIES */
+	len += nla_total_size(0);
+	if (data->capability.supported_caps & PHY_MSE_CAP_AVG)
+		/* ETHTOOL_A_MSE_CAPABILITIES_MAX_AVERAGE_MSE */
+		len += nla_total_size(sizeof(u64));
+	if (data->capability.supported_caps & (PHY_MSE_CAP_PEAK |
+					       PHY_MSE_CAP_WORST_PEAK))
+		/* ETHTOOL_A_MSE_CAPABILITIES_MAX_PEAK_MSE */
+		len += nla_total_size(sizeof(u64));
+	/* ETHTOOL_A_MSE_CAPABILITIES_REFRESH_RATE_PS */
+	len += nla_total_size(sizeof(u64));
+	/* ETHTOOL_A_MSE_CAPABILITIES_NUM_SYMBOLS */
+	len += nla_total_size(sizeof(u64));
+
+	for (i = 0; i < data->num_snapshots; i++) {
+		size_t snapshot_len = 0;
+
+		/* Per-channel nest (e.g., ETHTOOL_A_MSE_CHANNEL_A / _B / _C /
+		 * _D / _WORST_CHANNEL / _LINK)
+		 */
+		snapshot_len += nla_total_size(0);
+
+		if (data->capability.supported_caps & PHY_MSE_CAP_AVG)
+			snapshot_len += nla_total_size(sizeof(u64));
+		if (data->capability.supported_caps & PHY_MSE_CAP_PEAK)
+			snapshot_len += nla_total_size(sizeof(u64));
+		if (data->capability.supported_caps & PHY_MSE_CAP_WORST_PEAK)
+			snapshot_len += nla_total_size(sizeof(u64));
+
+		len += snapshot_len;
+	}
+
+	return len;
+}
+
+static int mse_channel_to_attr(int ch)
+{
+	switch (ch) {
+	case PHY_MSE_CHANNEL_A:
+		return ETHTOOL_A_MSE_CHANNEL_A;
+	case PHY_MSE_CHANNEL_B:
+		return ETHTOOL_A_MSE_CHANNEL_B;
+	case PHY_MSE_CHANNEL_C:
+		return ETHTOOL_A_MSE_CHANNEL_C;
+	case PHY_MSE_CHANNEL_D:
+		return ETHTOOL_A_MSE_CHANNEL_D;
+	case PHY_MSE_CHANNEL_WORST:
+		return ETHTOOL_A_MSE_WORST_CHANNEL;
+	case PHY_MSE_CHANNEL_LINK:
+		return ETHTOOL_A_MSE_LINK;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int mse_fill_reply(struct sk_buff *skb,
+			  const struct ethnl_req_info *req_base,
+			  const struct ethnl_reply_data *reply_base)
+{
+	const struct mse_reply_data *data = mse_repdata(reply_base);
+	struct nlattr *nest;
+	unsigned int i;
+	int ret;
+
+	nest = nla_nest_start(skb, ETHTOOL_A_MSE_CAPABILITIES);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (data->capability.supported_caps & PHY_MSE_CAP_AVG) {
+		ret = nla_put_uint(skb,
+				   ETHTOOL_A_MSE_CAPABILITIES_MAX_AVERAGE_MSE,
+				   data->capability.max_average_mse);
+		if (ret < 0)
+			goto nla_put_nest_failure;
+	}
+
+	if (data->capability.supported_caps & (PHY_MSE_CAP_PEAK |
+					       PHY_MSE_CAP_WORST_PEAK)) {
+		ret = nla_put_uint(skb, ETHTOOL_A_MSE_CAPABILITIES_MAX_PEAK_MSE,
+				   data->capability.max_peak_mse);
+		if (ret < 0)
+			goto nla_put_nest_failure;
+	}
+
+	ret = nla_put_uint(skb, ETHTOOL_A_MSE_CAPABILITIES_REFRESH_RATE_PS,
+			   data->capability.refresh_rate_ps);
+	if (ret < 0)
+		goto nla_put_nest_failure;
+
+	ret = nla_put_uint(skb, ETHTOOL_A_MSE_CAPABILITIES_NUM_SYMBOLS,
+			   data->capability.num_symbols);
+	if (ret < 0)
+		goto nla_put_nest_failure;
+
+	nla_nest_end(skb, nest);
+
+	for (i = 0; i < data->num_snapshots; i++) {
+		const struct mse_snapshot_entry *s = &data->snapshots[i];
+		int chan_attr;
+
+		chan_attr = mse_channel_to_attr(s->channel);
+		if (chan_attr < 0)
+			return chan_attr;
+
+		nest = nla_nest_start(skb, chan_attr);
+		if (!nest)
+			return -EMSGSIZE;
+
+		if (data->capability.supported_caps & PHY_MSE_CAP_AVG) {
+			ret = nla_put_uint(skb,
+					   ETHTOOL_A_MSE_SNAPSHOT_AVERAGE_MSE,
+					   s->snapshot.average_mse);
+			if (ret)
+				goto nla_put_nest_failure;
+		}
+		if (data->capability.supported_caps & PHY_MSE_CAP_PEAK) {
+			ret = nla_put_uint(skb, ETHTOOL_A_MSE_SNAPSHOT_PEAK_MSE,
+					   s->snapshot.peak_mse);
+			if (ret)
+				goto nla_put_nest_failure;
+		}
+		if (data->capability.supported_caps & PHY_MSE_CAP_WORST_PEAK) {
+			ret = nla_put_uint(skb,
+					   ETHTOOL_A_MSE_SNAPSHOT_WORST_PEAK_MSE,
+					   s->snapshot.worst_peak_mse);
+			if (ret)
+				goto nla_put_nest_failure;
+		}
+
+		nla_nest_end(skb, nest);
+	}
+
+	return 0;
+
+nla_put_nest_failure:
+	nla_nest_cancel(skb, nest);
+	return ret;
+}
+
+const struct ethnl_request_ops ethnl_mse_request_ops = {
+	.request_cmd = ETHTOOL_MSG_MSE_GET,
+	.reply_cmd = ETHTOOL_MSG_MSE_GET_REPLY,
+	.hdr_attr = ETHTOOL_A_MSE_HEADER,
+	.req_info_size = sizeof(struct mse_req_info),
+	.reply_data_size = sizeof(struct mse_reply_data),
+
+	.prepare_data = mse_prepare_data,
+	.cleanup_data = mse_cleanup_data,
+	.reply_size = mse_reply_size,
+	.fill_reply = mse_fill_reply,
+};
diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 2f813f25f07e..6e5f0f4f815a 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -420,6 +420,7 @@ ethnl_default_requests[__ETHTOOL_MSG_USER_CNT] = {
 	[ETHTOOL_MSG_TSCONFIG_GET]	= &ethnl_tsconfig_request_ops,
 	[ETHTOOL_MSG_TSCONFIG_SET]	= &ethnl_tsconfig_request_ops,
 	[ETHTOOL_MSG_PHY_GET]		= &ethnl_phy_request_ops,
+	[ETHTOOL_MSG_MSE_GET]		= &ethnl_mse_request_ops,
 };
 
 static struct ethnl_dump_ctx *ethnl_dump_context(struct netlink_callback *cb)
@@ -1534,6 +1535,15 @@ static const struct genl_ops ethtool_genl_ops[] = {
 		.policy	= ethnl_rss_delete_policy,
 		.maxattr = ARRAY_SIZE(ethnl_rss_delete_policy) - 1,
 	},
+	{
+		.cmd	= ETHTOOL_MSG_MSE_GET,
+		.doit	= ethnl_default_doit,
+		.start	= ethnl_perphy_start,
+		.dumpit	= ethnl_perphy_dumpit,
+		.done	= ethnl_perphy_done,
+		.policy = ethnl_mse_get_policy,
+		.maxattr = ARRAY_SIZE(ethnl_mse_get_policy) - 1,
+	},
 };
 
 static const struct genl_multicast_group ethtool_nl_mcgrps[] = {
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index 1d4f9ecb3d26..89010eaa67df 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -442,6 +442,7 @@ extern const struct ethnl_request_ops ethnl_plca_status_request_ops;
 extern const struct ethnl_request_ops ethnl_mm_request_ops;
 extern const struct ethnl_request_ops ethnl_phy_request_ops;
 extern const struct ethnl_request_ops ethnl_tsconfig_request_ops;
+extern const struct ethnl_request_ops ethnl_mse_request_ops;
 
 extern const struct nla_policy ethnl_header_policy[ETHTOOL_A_HEADER_FLAGS + 1];
 extern const struct nla_policy ethnl_header_policy_stats[ETHTOOL_A_HEADER_FLAGS + 1];
@@ -497,6 +498,7 @@ extern const struct nla_policy ethnl_module_fw_flash_act_policy[ETHTOOL_A_MODULE
 extern const struct nla_policy ethnl_phy_get_policy[ETHTOOL_A_PHY_HEADER + 1];
 extern const struct nla_policy ethnl_tsconfig_get_policy[ETHTOOL_A_TSCONFIG_HEADER + 1];
 extern const struct nla_policy ethnl_tsconfig_set_policy[ETHTOOL_A_TSCONFIG_MAX + 1];
+extern const struct nla_policy ethnl_mse_get_policy[ETHTOOL_A_MSE_HEADER + 1];
 
 int ethnl_set_features(struct sk_buff *skb, struct genl_info *info);
 int ethnl_act_cable_test(struct sk_buff *skb, struct genl_info *info);