devlink: define enum for attr types of dynamic attributes

Devlink param and health reporter fmsg use attributes with dynamic type
which is determined according to a different type. Currently used values
are NLA_*. The problem is, they are not part of UAPI. They may change
which would cause a break.

To make this future safe, introduce a enum that shadows NLA_* values in
it and is part of UAPI.

Also, this allows to possibly carry types that are unrelated to NLA_*
values.

Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Link: https://patch.msgid.link/20250505114513.53370-3-jiri@resnulli.us
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/devlink.yaml

@@ -202,6 +202,28 @@ definitions:
         name: exception
       -
         name: control
+  -
+    type: enum
+    name: var-attr-type
+    entries:
+      -
+        name: u8
+        value: 1
+      -
+        name: u16
+      -
+        name: u32
+      -
+        name: u64
+      -
+        name: string
+      -
+        name: flag
+      -
+        name: nul_string
+        value: 10
+      -
+        name: binary
 
 attribute-sets:
   -
@@ -498,6 +520,7 @@ attribute-sets:
       -
         name: param-type
         type: u8
+        enum: var-attr-type
 
       # TODO: fill in the attributes in between
 
@@ -592,6 +615,7 @@ attribute-sets:
       -
         name: fmsg-obj-value-type
         type: u8
+        enum: var-attr-type
 
       # TODO: fill in the attributes in between
 

include/uapi/linux/devlink.h

@@ -385,6 +385,21 @@ enum devlink_linecard_state {
 	DEVLINK_LINECARD_STATE_MAX = __DEVLINK_LINECARD_STATE_MAX - 1
 };
 
+/* Variable attribute type. */
+enum devlink_var_attr_type {
+	/* Following values relate to the internal NLA_* values */
+	DEVLINK_VAR_ATTR_TYPE_U8 = 1,
+	DEVLINK_VAR_ATTR_TYPE_U16,
+	DEVLINK_VAR_ATTR_TYPE_U32,
+	DEVLINK_VAR_ATTR_TYPE_U64,
+	DEVLINK_VAR_ATTR_TYPE_STRING,
+	DEVLINK_VAR_ATTR_TYPE_FLAG,
+	DEVLINK_VAR_ATTR_TYPE_NUL_STRING = 10,
+	DEVLINK_VAR_ATTR_TYPE_BINARY,
+	__DEVLINK_VAR_ATTR_TYPE_CUSTOM_BASE = 0x80,
+	/* Any possible custom types, unrelated to NLA_* values go below */
+};
+
 enum devlink_attr {
 	/* don't change the order or add anything between, this is ABI! */
 	DEVLINK_ATTR_UNSPEC,

net/devlink/health.c

@@ -930,18 +930,31 @@ EXPORT_SYMBOL_GPL(devlink_fmsg_binary_pair_put);
 static int
 devlink_fmsg_item_fill_type(struct devlink_fmsg_item *msg, struct sk_buff *skb)
 {
+	enum devlink_var_attr_type var_attr_type;
+
 	switch (msg->nla_type) {
 	case NLA_FLAG:
+		var_attr_type = DEVLINK_VAR_ATTR_TYPE_FLAG;
+		break;
 	case NLA_U8:
+		var_attr_type = DEVLINK_VAR_ATTR_TYPE_U8;
+		break;
 	case NLA_U32:
+		var_attr_type = DEVLINK_VAR_ATTR_TYPE_U32;
+		break;
 	case NLA_U64:
+		var_attr_type = DEVLINK_VAR_ATTR_TYPE_U64;
+		break;
 	case NLA_NUL_STRING:
+		var_attr_type = DEVLINK_VAR_ATTR_TYPE_NUL_STRING;
+		break;
 	case NLA_BINARY:
-		return nla_put_u8(skb, DEVLINK_ATTR_FMSG_OBJ_VALUE_TYPE,
+		var_attr_type = DEVLINK_VAR_ATTR_TYPE_BINARY;
-				  msg->nla_type);
+		break;
 	default:
 		return -EINVAL;
 	}
+	return nla_put_u8(skb, DEVLINK_ATTR_FMSG_OBJ_VALUE_TYPE, var_attr_type);
 }
 
 static int

net/devlink/netlink_gen.c

@@ -10,6 +10,33 @@
 
 #include <uapi/linux/devlink.h>
 
+/* Sparse enums validation callbacks */
+static int
+devlink_attr_param_type_validate(const struct nlattr *attr,
+				 struct netlink_ext_ack *extack)
+{
+	switch (nla_get_u8(attr)) {
+	case DEVLINK_VAR_ATTR_TYPE_U8:
+		fallthrough;
+	case DEVLINK_VAR_ATTR_TYPE_U16:
+		fallthrough;
+	case DEVLINK_VAR_ATTR_TYPE_U32:
+		fallthrough;
+	case DEVLINK_VAR_ATTR_TYPE_U64:
+		fallthrough;
+	case DEVLINK_VAR_ATTR_TYPE_STRING:
+		fallthrough;
+	case DEVLINK_VAR_ATTR_TYPE_FLAG:
+		fallthrough;
+	case DEVLINK_VAR_ATTR_TYPE_NUL_STRING:
+		fallthrough;
+	case DEVLINK_VAR_ATTR_TYPE_BINARY:
+		return 0;
+	}
+	NL_SET_ERR_MSG_ATTR(extack, attr, "invalid enum value");
+	return -EINVAL;
+}
+
 /* Common nested types */
 const struct nla_policy devlink_dl_port_function_nl_policy[DEVLINK_PORT_FN_ATTR_CAPS + 1] = {
 	[DEVLINK_PORT_FUNCTION_ATTR_HW_ADDR] = { .type = NLA_BINARY, },
@@ -273,7 +300,7 @@ static const struct nla_policy devlink_param_set_nl_policy[DEVLINK_ATTR_PARAM_VA
 	[DEVLINK_ATTR_BUS_NAME] = { .type = NLA_NUL_STRING, },
 	[DEVLINK_ATTR_DEV_NAME] = { .type = NLA_NUL_STRING, },
 	[DEVLINK_ATTR_PARAM_NAME] = { .type = NLA_NUL_STRING, },
-	[DEVLINK_ATTR_PARAM_TYPE] = { .type = NLA_U8, },
+	[DEVLINK_ATTR_PARAM_TYPE] = NLA_POLICY_VALIDATE_FN(NLA_U8, &devlink_attr_param_type_validate),
 	[DEVLINK_ATTR_PARAM_VALUE_CMODE] = NLA_POLICY_MAX(NLA_U8, 2),
 };
 

net/devlink/param.c

@@ -167,19 +167,19 @@ static int devlink_param_set(struct devlink *devlink,
 }
 
 static int
-devlink_param_type_to_nla_type(enum devlink_param_type param_type)
+devlink_param_type_to_var_attr_type(enum devlink_param_type param_type)
 {
 	switch (param_type) {
 	case DEVLINK_PARAM_TYPE_U8:
-		return NLA_U8;
+		return DEVLINK_VAR_ATTR_TYPE_U8;
 	case DEVLINK_PARAM_TYPE_U16:
-		return NLA_U16;
+		return DEVLINK_VAR_ATTR_TYPE_U16;
 	case DEVLINK_PARAM_TYPE_U32:
-		return NLA_U32;
+		return DEVLINK_VAR_ATTR_TYPE_U32;
 	case DEVLINK_PARAM_TYPE_STRING:
-		return NLA_STRING;
+		return DEVLINK_VAR_ATTR_TYPE_STRING;
 	case DEVLINK_PARAM_TYPE_BOOL:
-		return NLA_FLAG;
+		return DEVLINK_VAR_ATTR_TYPE_FLAG;
 	default:
 		return -EINVAL;
 	}
@@ -247,7 +247,7 @@ static int devlink_nl_param_fill(struct sk_buff *msg, struct devlink *devlink,
 	struct devlink_param_gset_ctx ctx;
 	struct nlattr *param_values_list;
 	struct nlattr *param_attr;
-	int nla_type;
+	int var_attr_type;
 	void *hdr;
 	int err;
 	int i;
@@ -294,10 +294,10 @@ static int devlink_nl_param_fill(struct sk_buff *msg, struct devlink *devlink,
 	if (param->generic && nla_put_flag(msg, DEVLINK_ATTR_PARAM_GENERIC))
 		goto param_nest_cancel;
 
-	nla_type = devlink_param_type_to_nla_type(param->type);
+	var_attr_type = devlink_param_type_to_var_attr_type(param->type);
-	if (nla_type < 0)
+	if (var_attr_type < 0)
 		goto param_nest_cancel;
-	if (nla_put_u8(msg, DEVLINK_ATTR_PARAM_TYPE, nla_type))
+	if (nla_put_u8(msg, DEVLINK_ATTR_PARAM_TYPE, var_attr_type))
 		goto param_nest_cancel;
 
 	param_values_list = nla_nest_start_noflag(msg,
@@ -420,19 +420,19 @@ devlink_param_type_get_from_info(struct genl_info *info,
 		return -EINVAL;
 
 	switch (nla_get_u8(info->attrs[DEVLINK_ATTR_PARAM_TYPE])) {
-	case NLA_U8:
+	case DEVLINK_VAR_ATTR_TYPE_U8:
 		*param_type = DEVLINK_PARAM_TYPE_U8;
 		break;
-	case NLA_U16:
+	case DEVLINK_VAR_ATTR_TYPE_U16:
 		*param_type = DEVLINK_PARAM_TYPE_U16;
 		break;
-	case NLA_U32:
+	case DEVLINK_VAR_ATTR_TYPE_U32:
 		*param_type = DEVLINK_PARAM_TYPE_U32;
 		break;
-	case NLA_STRING:
+	case DEVLINK_VAR_ATTR_TYPE_STRING:
 		*param_type = DEVLINK_PARAM_TYPE_STRING;
 		break;
-	case NLA_FLAG:
+	case DEVLINK_VAR_ATTR_TYPE_FLAG:
 		*param_type = DEVLINK_PARAM_TYPE_BOOL;
 		break;
 	default: