Merge branch 'ethtool-fec-netlink'

Jakub Kicinski says:

====================
ethtool: support FEC configuration over netlink

This series adds support for the equivalents of ETHTOOL_GFECPARAM
and ETHTOOL_SFECPARAM over netlink.

As a reminder - this is an API which allows user to query current
FEC mode, as well as set FEC manually if autoneg is disabled.
It does not configure anything if autoneg is enabled (that said
few/no drivers currently reject .set_fecparam calls while autoneg
is disabled, hopefully FW will just ignore the settings).

The existing functionality is mostly preserved in the new API.
The ioctl interface uses a set of flags, and link modes to tell
user which modes are supported. Here is how the flags translate
to the new interface (skipping descriptions for actual FEC modes):

  ioctl flag      |   description         |  new API
================================================================
ETHTOOL_FEC_OFF   | disabled (supported)  | \
ETHTOOL_FEC_RS    |                       |  ` link mode bitset
ETHTOOL_FEC_BASER |                       |  / .._A_FEC_MODES
ETHTOOL_FEC_LLRS  |                       | /
ETHTOOL_FEC_AUTO  | pick based on cable   | bool .._A_FEC_AUTO
ETHTOOL_FEC_NONE  | not supported         | no bit, no AUTO reported

Since link modes are already depended on (although somewhat implicitly)
for expressing supported modes - the new interface uses them for
the manual configuration, as well as uses link mode bit number
to communicate the active mode.

Use of link modes allows us to define any number of FEC modes we want,
and reuse the strset we already have defined.

Separating AUTO as its own attribute is the biggest changed compared
to the ioctl. It means drivers can no longer report AUTO as the
active FEC mode because there is no link mode for AUTO.
active_fec == AUTO makes little sense in the first place IMHO,
active_fec should be the actual mode, so hopefully this is fine.

The other minor departure is that None is no longer explicitly
expressed in the API. But drivers are reasonable in handling of
this somewhat pointless bit, so I'm not expecting any issues there.

One extension which could be considered would be moving active FEC
to ETHTOOL_MSG_LINKMODE_*, but then why not move all of FEC into
link modes? I don't know where to draw the line.

netdevsim support and a simple self test are included.

Next step is adding stats similar to the ones added for pause.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

,

Documentation/networking/ethtool-netlink.rst

@@ -208,6 +208,8 @@ Userspace to kernel:
   ``ETHTOOL_MSG_CABLE_TEST_ACT``        action start cable test
   ``ETHTOOL_MSG_CABLE_TEST_TDR_ACT``    action start raw TDR cable test
   ``ETHTOOL_MSG_TUNNEL_INFO_GET``       get tunnel offload info
+  ``ETHTOOL_MSG_FEC_GET``               get FEC settings
+  ``ETHTOOL_MSG_FEC_SET``               set FEC settings
   ===================================== ================================
 
 Kernel to userspace:
@@ -242,6 +244,8 @@ Kernel to userspace:
   ``ETHTOOL_MSG_CABLE_TEST_NTF``        Cable test results
   ``ETHTOOL_MSG_CABLE_TEST_TDR_NTF``    Cable test TDR results
   ``ETHTOOL_MSG_TUNNEL_INFO_GET_REPLY`` tunnel offload info
+  ``ETHTOOL_MSG_FEC_GET_REPLY``         FEC settings
+  ``ETHTOOL_MSG_FEC_NTF``               FEC settings
   ===================================== =================================
 
 ``GET`` requests are sent by userspace applications to retrieve device
@@ -1280,6 +1284,60 @@ Kernel response contents:
 For UDP tunnel table empty ``ETHTOOL_A_TUNNEL_UDP_TABLE_TYPES`` indicates that
 the table contains static entries, hard-coded by the NIC.
 
+FEC_GET
+=======
+
+Gets FEC configuration and state like ``ETHTOOL_GFECPARAM`` ioctl request.
+
+Request contents:
+
+  =====================================  ======  ==========================
+  ``ETHTOOL_A_FEC_HEADER``               nested  request header
+  =====================================  ======  ==========================
+
+Kernel response contents:
+
+  =====================================  ======  ==========================
+  ``ETHTOOL_A_FEC_HEADER``               nested  request header
+  ``ETHTOOL_A_FEC_MODES``                bitset  configured modes
+  ``ETHTOOL_A_FEC_AUTO``                 bool    FEC mode auto selection
+  ``ETHTOOL_A_FEC_ACTIVE``               u32     index of active FEC mode
+  =====================================  ======  ==========================
+
+``ETHTOOL_A_FEC_ACTIVE`` is the bit index of the FEC link mode currently
+active on the interface. This attribute may not be present if device does
+not support FEC.
+
+``ETHTOOL_A_FEC_MODES`` and ``ETHTOOL_A_FEC_AUTO`` are only meaningful when
+autonegotiation is disabled. If ``ETHTOOL_A_FEC_AUTO`` is non-zero driver will
+select the FEC mode automatically based on the parameters of the SFP module.
+This is equivalent to the ``ETHTOOL_FEC_AUTO`` bit of the ioctl interface.
+``ETHTOOL_A_FEC_MODES`` carry the current FEC configuration using link mode
+bits (rather than old ``ETHTOOL_FEC_*`` bits).
+
+FEC_SET
+=======
+
+Sets FEC parameters like ``ETHTOOL_SFECPARAM`` ioctl request.
+
+Request contents:
+
+  =====================================  ======  ==========================
+  ``ETHTOOL_A_FEC_HEADER``               nested  request header
+  ``ETHTOOL_A_FEC_MODES``                bitset  configured modes
+  ``ETHTOOL_A_FEC_AUTO``                 bool    FEC mode auto selection
+  =====================================  ======  ==========================
+
+``FEC_SET`` is only meaningful when autonegotiation is disabled. Otherwise
+FEC mode is selected as part of autonegotiation.
+
+``ETHTOOL_A_FEC_MODES`` selects which FEC mode should be used. It's recommended
+to set only one bit, if multiple bits are set driver may choose between them
+in an implementation specific way.
+
+``ETHTOOL_A_FEC_AUTO`` requests the driver to choose FEC mode based on SFP
+module parameters. This does not mean autonegotiation.
+
 Request translation
 ===================
 
@@ -1373,8 +1431,8 @@ are netlink only.
                                       ``ETHTOOL_MSG_LINKMODES_SET``
   ``ETHTOOL_PHY_GTUNABLE``            n/a
   ``ETHTOOL_PHY_STUNABLE``            n/a
-  ``ETHTOOL_GFECPARAM``               n/a
-  ``ETHTOOL_SFECPARAM``               n/a
+  ``ETHTOOL_GFECPARAM``               ``ETHTOOL_MSG_FEC_GET``
+  ``ETHTOOL_SFECPARAM``               ``ETHTOOL_MSG_FEC_SET``
   n/a                                 ''ETHTOOL_MSG_CABLE_TEST_ACT''
   n/a                                 ''ETHTOOL_MSG_CABLE_TEST_TDR_ACT''
   n/a                                 ``ETHTOOL_MSG_TUNNEL_INFO_GET``

drivers/net/netdevsim/ethtool.c

@@ -77,6 +77,34 @@ static int nsim_set_ringparam(struct net_device *dev,
 	return 0;
 }
 
+static int
+nsim_get_fecparam(struct net_device *dev, struct ethtool_fecparam *fecparam)
+{
+	struct netdevsim *ns = netdev_priv(dev);
+
+	if (ns->ethtool.get_err)
+		return -ns->ethtool.get_err;
+	memcpy(fecparam, &ns->ethtool.fec, sizeof(ns->ethtool.fec));
+	return 0;
+}
+
+static int
+nsim_set_fecparam(struct net_device *dev, struct ethtool_fecparam *fecparam)
+{
+	struct netdevsim *ns = netdev_priv(dev);
+	u32 fec;
+
+	if (ns->ethtool.set_err)
+		return -ns->ethtool.set_err;
+	memcpy(&ns->ethtool.fec, fecparam, sizeof(ns->ethtool.fec));
+	fec = fecparam->fec;
+	if (fec == ETHTOOL_FEC_AUTO)
+		fec |= ETHTOOL_FEC_OFF;
+	fec |= ETHTOOL_FEC_NONE;
+	ns->ethtool.fec.active_fec = 1 << (fls(fec) - 1);
+	return 0;
+}
+
 static const struct ethtool_ops nsim_ethtool_ops = {
 	.supported_coalesce_params	= ETHTOOL_COALESCE_ALL_PARAMS,
 	.get_pause_stats	        = nsim_get_pause_stats,
@@ -86,6 +114,8 @@ static const struct ethtool_ops nsim_ethtool_ops = {
 	.get_coalesce			= nsim_get_coalesce,
 	.get_ringparam			= nsim_get_ringparam,
 	.set_ringparam			= nsim_set_ringparam,
+	.get_fecparam			= nsim_get_fecparam,
+	.set_fecparam			= nsim_set_fecparam,
 };
 
 static void nsim_ethtool_ring_init(struct netdevsim *ns)
@@ -104,8 +134,14 @@ void nsim_ethtool_init(struct netdevsim *ns)
 
 	nsim_ethtool_ring_init(ns);
 
+	ns->ethtool.fec.fec = ETHTOOL_FEC_NONE;
+	ns->ethtool.fec.active_fec = ETHTOOL_FEC_NONE;
+
 	ethtool = debugfs_create_dir("ethtool", ns->nsim_dev_port->ddir);
 
+	debugfs_create_u32("get_err", 0600, ethtool, &ns->ethtool.get_err);
+	debugfs_create_u32("set_err", 0600, ethtool, &ns->ethtool.set_err);
+
 	dir = debugfs_create_dir("pause", ethtool);
 	debugfs_create_bool("report_stats_rx", 0600, dir,
 			    &ns->ethtool.pauseparam.report_stats_rx);

drivers/net/netdevsim/netdevsim.h

@@ -60,9 +60,12 @@ struct nsim_ethtool_pauseparam {
 };
 
 struct nsim_ethtool {
+	u32 get_err;
+	u32 set_err;
 	struct nsim_ethtool_pauseparam pauseparam;
 	struct ethtool_coalesce coalesce;
 	struct ethtool_ringparam ring;
+	struct ethtool_fecparam fec;
 };
 
 struct netdevsim {

include/uapi/linux/ethtool_netlink.h

@@ -42,6 +42,8 @@ enum {
 	ETHTOOL_MSG_CABLE_TEST_ACT,
 	ETHTOOL_MSG_CABLE_TEST_TDR_ACT,
 	ETHTOOL_MSG_TUNNEL_INFO_GET,
+	ETHTOOL_MSG_FEC_GET,
+	ETHTOOL_MSG_FEC_SET,
 
 	/* add new constants above here */
 	__ETHTOOL_MSG_USER_CNT,
@@ -80,6 +82,8 @@ enum {
 	ETHTOOL_MSG_CABLE_TEST_NTF,
 	ETHTOOL_MSG_CABLE_TEST_TDR_NTF,
 	ETHTOOL_MSG_TUNNEL_INFO_GET_REPLY,
+	ETHTOOL_MSG_FEC_GET_REPLY,
+	ETHTOOL_MSG_FEC_NTF,
 
 	/* add new constants above here */
 	__ETHTOOL_MSG_KERNEL_CNT,
@@ -629,6 +633,19 @@ enum {
 	ETHTOOL_A_TUNNEL_INFO_MAX = (__ETHTOOL_A_TUNNEL_INFO_CNT - 1)
 };
 
+/* FEC */
+
+enum {
+	ETHTOOL_A_FEC_UNSPEC,
+	ETHTOOL_A_FEC_HEADER,				/* nest - _A_HEADER_* */
+	ETHTOOL_A_FEC_MODES,				/* bitset */
+	ETHTOOL_A_FEC_AUTO,				/* u8 */
+	ETHTOOL_A_FEC_ACTIVE,				/* u32 */
+
+	__ETHTOOL_A_FEC_CNT,
+	ETHTOOL_A_FEC_MAX = (__ETHTOOL_A_FEC_CNT - 1)
+};
+
 /* generic netlink info */
 #define ETHTOOL_GENL_NAME "ethtool"
 #define ETHTOOL_GENL_VERSION 1

net/ethtool/Makefile

@@ -7,4 +7,4 @@ obj-$(CONFIG_ETHTOOL_NETLINK)	+= ethtool_nl.o
 ethtool_nl-y	:= netlink.o bitset.o strset.o linkinfo.o linkmodes.o \
 		   linkstate.o debug.o wol.o features.o privflags.o rings.o \
 		   channels.o coalesce.o pause.o eee.o tsinfo.o cabletest.o \
-		   tunnels.o
+		   tunnels.o fec.o

net/ethtool/fec.c

+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "netlink.h"
+#include "common.h"
+#include "bitset.h"
+
+struct fec_req_info {
+	struct ethnl_req_info		base;
+};
+
+struct fec_reply_data {
+	struct ethnl_reply_data		base;
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(fec_link_modes);
+	u32 active_fec;
+	u8 fec_auto;
+};
+
+#define FEC_REPDATA(__reply_base) \
+	container_of(__reply_base, struct fec_reply_data, base)
+
+#define ETHTOOL_FEC_MASK	((ETHTOOL_FEC_LLRS << 1) - 1)
+
+const struct nla_policy ethnl_fec_get_policy[ETHTOOL_A_FEC_HEADER + 1] = {
+	[ETHTOOL_A_FEC_HEADER]	= NLA_POLICY_NESTED(ethnl_header_policy),
+};
+
+static void
+ethtool_fec_to_link_modes(u32 fec, unsigned long *link_modes, u8 *fec_auto)
+{
+	if (fec_auto)
+		*fec_auto = !!(fec & ETHTOOL_FEC_AUTO);
+
+	if (fec & ETHTOOL_FEC_OFF)
+		__set_bit(ETHTOOL_LINK_MODE_FEC_NONE_BIT, link_modes);
+	if (fec & ETHTOOL_FEC_RS)
+		__set_bit(ETHTOOL_LINK_MODE_FEC_RS_BIT, link_modes);
+	if (fec & ETHTOOL_FEC_BASER)
+		__set_bit(ETHTOOL_LINK_MODE_FEC_BASER_BIT, link_modes);
+	if (fec & ETHTOOL_FEC_LLRS)
+		__set_bit(ETHTOOL_LINK_MODE_FEC_LLRS_BIT, link_modes);
+}
+
+static int
+ethtool_link_modes_to_fecparam(struct ethtool_fecparam *fec,
+			       unsigned long *link_modes, u8 fec_auto)
+{
+	memset(fec, 0, sizeof(*fec));
+
+	if (fec_auto)
+		fec->fec |= ETHTOOL_FEC_AUTO;
+
+	if (__test_and_clear_bit(ETHTOOL_LINK_MODE_FEC_NONE_BIT, link_modes))
+		fec->fec |= ETHTOOL_FEC_OFF;
+	if (__test_and_clear_bit(ETHTOOL_LINK_MODE_FEC_RS_BIT, link_modes))
+		fec->fec |= ETHTOOL_FEC_RS;
+	if (__test_and_clear_bit(ETHTOOL_LINK_MODE_FEC_BASER_BIT, link_modes))
+		fec->fec |= ETHTOOL_FEC_BASER;
+	if (__test_and_clear_bit(ETHTOOL_LINK_MODE_FEC_LLRS_BIT, link_modes))
+		fec->fec |= ETHTOOL_FEC_LLRS;
+
+	if (!bitmap_empty(link_modes, __ETHTOOL_LINK_MODE_MASK_NBITS))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int fec_prepare_data(const struct ethnl_req_info *req_base,
+			    struct ethnl_reply_data *reply_base,
+			    struct genl_info *info)
+{
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(active_fec_modes) = {};
+	struct fec_reply_data *data = FEC_REPDATA(reply_base);
+	struct net_device *dev = reply_base->dev;
+	struct ethtool_fecparam fec = {};
+	int ret;
+
+	if (!dev->ethtool_ops->get_fecparam)
+		return -EOPNOTSUPP;
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		return ret;
+	ret = dev->ethtool_ops->get_fecparam(dev, &fec);
+	ethnl_ops_complete(dev);
+	if (ret)
+		return ret;
+
+	WARN_ON_ONCE(fec.reserved);
+
+	ethtool_fec_to_link_modes(fec.fec, data->fec_link_modes,
+				  &data->fec_auto);
+
+	ethtool_fec_to_link_modes(fec.active_fec, active_fec_modes, NULL);
+	data->active_fec = find_first_bit(active_fec_modes,
+					  __ETHTOOL_LINK_MODE_MASK_NBITS);
+	/* Don't report attr if no FEC mode set. Note that
+	 * ethtool_fecparam_to_link_modes() ignores NONE and AUTO.
+	 */
+	if (data->active_fec == __ETHTOOL_LINK_MODE_MASK_NBITS)
+		data->active_fec = 0;
+
+	return 0;
+}
+
+static int fec_reply_size(const struct ethnl_req_info *req_base,
+			  const struct ethnl_reply_data *reply_base)
+{
+	bool compact = req_base->flags & ETHTOOL_FLAG_COMPACT_BITSETS;
+	const struct fec_reply_data *data = FEC_REPDATA(reply_base);
+	int len = 0;
+	int ret;
+
+	ret = ethnl_bitset_size(data->fec_link_modes, NULL,
+				__ETHTOOL_LINK_MODE_MASK_NBITS,
+				link_mode_names, compact);
+	if (ret < 0)
+		return ret;
+	len += ret;
+
+	len += nla_total_size(sizeof(u8)) +	/* _FEC_AUTO */
+	       nla_total_size(sizeof(u32));	/* _FEC_ACTIVE */
+
+	return len;
+}
+
+static int fec_fill_reply(struct sk_buff *skb,
+			  const struct ethnl_req_info *req_base,
+			  const struct ethnl_reply_data *reply_base)
+{
+	bool compact = req_base->flags & ETHTOOL_FLAG_COMPACT_BITSETS;
+	const struct fec_reply_data *data = FEC_REPDATA(reply_base);
+	int ret;
+
+	ret = ethnl_put_bitset(skb, ETHTOOL_A_FEC_MODES,
+			       data->fec_link_modes, NULL,
+			       __ETHTOOL_LINK_MODE_MASK_NBITS,
+			       link_mode_names, compact);
+	if (ret < 0)
+		return ret;
+
+	if (nla_put_u8(skb, ETHTOOL_A_FEC_AUTO, data->fec_auto) ||
+	    (data->active_fec &&
+	     nla_put_u32(skb, ETHTOOL_A_FEC_ACTIVE, data->active_fec)))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+const struct ethnl_request_ops ethnl_fec_request_ops = {
+	.request_cmd		= ETHTOOL_MSG_FEC_GET,
+	.reply_cmd		= ETHTOOL_MSG_FEC_GET_REPLY,
+	.hdr_attr		= ETHTOOL_A_FEC_HEADER,
+	.req_info_size		= sizeof(struct fec_req_info),
+	.reply_data_size	= sizeof(struct fec_reply_data),
+
+	.prepare_data		= fec_prepare_data,
+	.reply_size		= fec_reply_size,
+	.fill_reply		= fec_fill_reply,
+};
+
+/* FEC_SET */
+
+const struct nla_policy ethnl_fec_set_policy[ETHTOOL_A_FEC_AUTO + 1] = {
+	[ETHTOOL_A_FEC_HEADER]	= NLA_POLICY_NESTED(ethnl_header_policy),
+	[ETHTOOL_A_FEC_MODES]	= { .type = NLA_NESTED },
+	[ETHTOOL_A_FEC_AUTO]	= NLA_POLICY_MAX(NLA_U8, 1),
+};
+
+int ethnl_set_fec(struct sk_buff *skb, struct genl_info *info)
+{
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(fec_link_modes) = {};
+	struct ethnl_req_info req_info = {};
+	struct nlattr **tb = info->attrs;
+	struct ethtool_fecparam fec = {};
+	const struct ethtool_ops *ops;
+	struct net_device *dev;
+	bool mod = false;
+	u8 fec_auto;
+	int ret;
+
+	ret = ethnl_parse_header_dev_get(&req_info, tb[ETHTOOL_A_FEC_HEADER],
+					 genl_info_net(info), info->extack,
+					 true);
+	if (ret < 0)
+		return ret;
+	dev = req_info.dev;
+	ops = dev->ethtool_ops;
+	ret = -EOPNOTSUPP;
+	if (!ops->get_fecparam || !ops->set_fecparam)
+		goto out_dev;
+
+	rtnl_lock();
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		goto out_rtnl;
+	ret = ops->get_fecparam(dev, &fec);
+	if (ret < 0)
+		goto out_ops;
+
+	ethtool_fec_to_link_modes(fec.fec, fec_link_modes, &fec_auto);
+
+	ret = ethnl_update_bitset(fec_link_modes,
+				  __ETHTOOL_LINK_MODE_MASK_NBITS,
+				  tb[ETHTOOL_A_FEC_MODES],
+				  link_mode_names, info->extack, &mod);
+	if (ret < 0)
+		goto out_ops;
+	ethnl_update_u8(&fec_auto, tb[ETHTOOL_A_FEC_AUTO], &mod);
+
+	ret = 0;
+	if (!mod)
+		goto out_ops;
+
+	ret = ethtool_link_modes_to_fecparam(&fec, fec_link_modes, fec_auto);
+	if (ret) {
+		NL_SET_ERR_MSG_ATTR(info->extack, tb[ETHTOOL_A_FEC_MODES],
+				    "invalid FEC modes requested");
+		goto out_ops;
+	}
+	if (!fec.fec) {
+		ret = -EINVAL;
+		NL_SET_ERR_MSG_ATTR(info->extack, tb[ETHTOOL_A_FEC_MODES],
+				    "no FEC modes set");
+		goto out_ops;
+	}
+
+	ret = dev->ethtool_ops->set_fecparam(dev, &fec);
+	if (ret < 0)
+		goto out_ops;
+	ethtool_notify(dev, ETHTOOL_MSG_FEC_NTF, NULL);
+
+out_ops:
+	ethnl_ops_complete(dev);
+out_rtnl:
+	rtnl_unlock();
+out_dev:
+	dev_put(dev);
+	return ret;
+}

net/ethtool/netlink.c

@@ -244,6 +244,7 @@ ethnl_default_requests[__ETHTOOL_MSG_USER_CNT] = {
 	[ETHTOOL_MSG_COALESCE_GET]	= &ethnl_coalesce_request_ops,
 	[ETHTOOL_MSG_PAUSE_GET]		= &ethnl_pause_request_ops,
 	[ETHTOOL_MSG_EEE_GET]		= &ethnl_eee_request_ops,
+	[ETHTOOL_MSG_FEC_GET]		= &ethnl_fec_request_ops,
 	[ETHTOOL_MSG_TSINFO_GET]	= &ethnl_tsinfo_request_ops,
 };
 
@@ -551,6 +552,7 @@ ethnl_default_notify_ops[ETHTOOL_MSG_KERNEL_MAX + 1] = {
 	[ETHTOOL_MSG_COALESCE_NTF]	= &ethnl_coalesce_request_ops,
 	[ETHTOOL_MSG_PAUSE_NTF]		= &ethnl_pause_request_ops,
 	[ETHTOOL_MSG_EEE_NTF]		= &ethnl_eee_request_ops,
+	[ETHTOOL_MSG_FEC_NTF]		= &ethnl_fec_request_ops,
 };
 
 /* default notification handler */
@@ -643,6 +645,7 @@ static const ethnl_notify_handler_t ethnl_notify_handlers[] = {
 	[ETHTOOL_MSG_COALESCE_NTF]	= ethnl_default_notify,
 	[ETHTOOL_MSG_PAUSE_NTF]		= ethnl_default_notify,
 	[ETHTOOL_MSG_EEE_NTF]		= ethnl_default_notify,
+	[ETHTOOL_MSG_FEC_NTF]		= ethnl_default_notify,
 };
 
 void ethtool_notify(struct net_device *dev, unsigned int cmd, const void *data)
@@ -912,6 +915,22 @@ static const struct genl_ops ethtool_genl_ops[] = {
 		.policy = ethnl_tunnel_info_get_policy,
 		.maxattr = ARRAY_SIZE(ethnl_tunnel_info_get_policy) - 1,
 	},
+	{
+		.cmd	= ETHTOOL_MSG_FEC_GET,
+		.doit	= ethnl_default_doit,
+		.start	= ethnl_default_start,
+		.dumpit	= ethnl_default_dumpit,
+		.done	= ethnl_default_done,
+		.policy = ethnl_fec_get_policy,
+		.maxattr = ARRAY_SIZE(ethnl_fec_get_policy) - 1,
+	},
+	{
+		.cmd	= ETHTOOL_MSG_FEC_SET,
+		.flags	= GENL_UNS_ADMIN_PERM,
+		.doit	= ethnl_set_fec,
+		.policy = ethnl_fec_set_policy,
+		.maxattr = ARRAY_SIZE(ethnl_fec_set_policy) - 1,
+	},
 };
 
 static const struct genl_multicast_group ethtool_nl_mcgrps[] = {

net/ethtool/netlink.h

@@ -344,6 +344,7 @@ extern const struct ethnl_request_ops ethnl_coalesce_request_ops;
 extern const struct ethnl_request_ops ethnl_pause_request_ops;
 extern const struct ethnl_request_ops ethnl_eee_request_ops;
 extern const struct ethnl_request_ops ethnl_tsinfo_request_ops;
+extern const struct ethnl_request_ops ethnl_fec_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];
@@ -375,6 +376,8 @@ extern const struct nla_policy ethnl_tsinfo_get_policy[ETHTOOL_A_TSINFO_HEADER +
 extern const struct nla_policy ethnl_cable_test_act_policy[ETHTOOL_A_CABLE_TEST_HEADER + 1];
 extern const struct nla_policy ethnl_cable_test_tdr_act_policy[ETHTOOL_A_CABLE_TEST_TDR_CFG + 1];
 extern const struct nla_policy ethnl_tunnel_info_get_policy[ETHTOOL_A_TUNNEL_INFO_HEADER + 1];
+extern const struct nla_policy ethnl_fec_get_policy[ETHTOOL_A_FEC_HEADER + 1];
+extern const struct nla_policy ethnl_fec_set_policy[ETHTOOL_A_FEC_AUTO + 1];
 
 int ethnl_set_linkinfo(struct sk_buff *skb, struct genl_info *info);
 int ethnl_set_linkmodes(struct sk_buff *skb, struct genl_info *info);
@@ -392,5 +395,6 @@ int ethnl_act_cable_test_tdr(struct sk_buff *skb, struct genl_info *info);
 int ethnl_tunnel_info_doit(struct sk_buff *skb, struct genl_info *info);
 int ethnl_tunnel_info_start(struct netlink_callback *cb);
 int ethnl_tunnel_info_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
+int ethnl_set_fec(struct sk_buff *skb, struct genl_info *info);
 
 #endif /* _NET_ETHTOOL_NETLINK_H */

tools/testing/selftests/drivers/net/netdevsim/ethtool-common.sh

@@ -24,8 +24,11 @@ function check {
     local code=$1
     local str=$2
     local exp_str=$3
+    local exp_fail=$4
 
-    if [ $code -ne 0 ]; then
+    [ -z "$exp_fail" ] && cop="-ne" || cop="-eq"
+
+    if [ $code $cop 0 ]; then
 	((num_errors++))
 	return
     fi

tools/testing/selftests/drivers/net/netdevsim/ethtool-fec.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+
+source ethtool-common.sh
+
+NSIM_NETDEV=$(make_netdev)
+[ a$ETHTOOL == a ] && ETHTOOL=ethtool
+
+set -o pipefail
+
+# netdevsim starts out with None/None
+s=$($ETHTOOL --show-fec $NSIM_NETDEV | tail -2)
+check $? "$s" "Configured FEC encodings: None
+Active FEC encoding: None"
+
+# Test Auto
+$ETHTOOL --set-fec $NSIM_NETDEV encoding auto
+check $?
+s=$($ETHTOOL --show-fec $NSIM_NETDEV | tail -2)
+check $? "$s" "Configured FEC encodings: Auto
+Active FEC encoding: Off"
+
+# Test case in-sensitivity
+for o in off Off OFF; do
+    $ETHTOOL --set-fec $NSIM_NETDEV encoding $o
+    check $?
+    s=$($ETHTOOL --show-fec $NSIM_NETDEV | tail -2)
+    check $? "$s" "Configured FEC encodings: Off
+Active FEC encoding: Off"
+done
+
+for o in BaseR baser BAser; do
+    $ETHTOOL --set-fec $NSIM_NETDEV encoding $o
+    check $?
+    s=$($ETHTOOL --show-fec $NSIM_NETDEV | tail -2)
+    check $? "$s" "Configured FEC encodings: BaseR
+Active FEC encoding: BaseR"
+done
+
+for o in llrs rs; do
+    $ETHTOOL --set-fec $NSIM_NETDEV encoding $o
+    check $?
+    s=$($ETHTOOL --show-fec $NSIM_NETDEV | tail -2)
+    check $? "$s" "Configured FEC encodings: ${o^^}
+Active FEC encoding: ${o^^}"
+done
+
+# Test mutliple bits
+$ETHTOOL --set-fec $NSIM_NETDEV encoding rs llrs
+check $?
+s=$($ETHTOOL --show-fec $NSIM_NETDEV | tail -2)
+check $? "$s" "Configured FEC encodings: RS LLRS
+Active FEC encoding: LLRS"
+
+$ETHTOOL --set-fec $NSIM_NETDEV encoding rs off auto
+check $?
+s=$($ETHTOOL --show-fec $NSIM_NETDEV | tail -2)
+check $? "$s" "Configured FEC encodings: Auto Off RS
+Active FEC encoding: RS"
+
+# Make sure other link modes are rejected
+$ETHTOOL --set-fec $NSIM_NETDEV encoding FIBRE 2>/dev/null
+check $? '' '' 1
+
+$ETHTOOL --set-fec $NSIM_NETDEV encoding bla-bla-bla 2>/dev/null
+check $? '' '' 1
+
+# Try JSON
+$ETHTOOL --json --show-fec $NSIM_NETDEV | jq empty >>/dev/null 2>&1
+if [ $? -eq 0 ]; then
+    $ETHTOOL --set-fec $NSIM_NETDEV encoding auto
+    check $?
+
+    s=$($ETHTOOL --json --show-fec $NSIM_NETDEV | jq '.[].config[]')
+    check $? "$s" '"Auto"'
+    s=$($ETHTOOL --json --show-fec $NSIM_NETDEV | jq '.[].active[]')
+    check $? "$s" '"Off"'
+
+    $ETHTOOL --set-fec $NSIM_NETDEV encoding auto RS
+    check $?
+
+    s=$($ETHTOOL --json --show-fec $NSIM_NETDEV | jq '.[].config[]')
+    check $? "$s" '"Auto"
+"RS"'
+    s=$($ETHTOOL --json --show-fec $NSIM_NETDEV | jq '.[].active[]')
+    check $? "$s" '"RS"'
+fi
+
+# Test error injection
+echo 11 > $NSIM_DEV_DFS/ethtool/get_err
+
+$ETHTOOL --show-fec $NSIM_NETDEV >>/dev/null 2>&1
+check $? '' '' 1
+
+echo 0 > $NSIM_DEV_DFS/ethtool/get_err
+echo 11 > $NSIM_DEV_DFS/ethtool/set_err
+
+$ETHTOOL --show-fec $NSIM_NETDEV  >>/dev/null 2>&1
+check $?
+
+$ETHTOOL --set-fec $NSIM_NETDEV encoding RS 2>/dev/null
+check $? '' '' 1
+
+if [ $num_errors -eq 0 ]; then
+    echo "PASSED all $((num_passes)) checks"
+    exit 0
+else
+    echo "FAILED $num_errors/$((num_errors+num_passes)) checks"
+    exit 1
+fi