devlink: Implement devlink param multi attribute nested data values

Devlink param value attribute is not defined since devlink is handling
the value validating and parsing internally, this allows us to implement
multi attribute values without breaking any policies.

Devlink param multi-attribute values are considered to be dynamically
sized arrays of u64 values, by introducing a new devlink param type
DEVLINK_PARAM_TYPE_U64_ARRAY, driver and user space can set a variable
count of u64 values into the DEVLINK_ATTR_PARAM_VALUE_DATA attribute.

Implement get/set parsing and add to the internal value structure passed
to drivers.

This is useful for devices that need to configure a list of values for
a specific configuration.

example:
$ devlink dev param show pci/... name multi-value-param
name multi-value-param type driver-specific
values:
cmode permanent value: 0,1,2,3,4,5,6,7

$ devlink dev param set pci/... name multi-value-param \
		value 4,5,6,7,0,1,2,3 cmode permanent

Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Ratheesh Kannoth <rkannoth@marvell.com>
Link: https://patch.msgid.link/20260609040453.711932-5-rkannoth@marvell.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/devlink.yaml

@@ -234,6 +234,10 @@ definitions:
         value: 10
       -
         name: binary
+      -
+        name: u64-array
+        value: 129
+
   -
     name: rate-tc-index-max
     type: const

include/net/devlink.h

@@ -433,6 +433,13 @@ enum devlink_param_type {
 	DEVLINK_PARAM_TYPE_U64 = DEVLINK_VAR_ATTR_TYPE_U64,
 	DEVLINK_PARAM_TYPE_STRING = DEVLINK_VAR_ATTR_TYPE_STRING,
 	DEVLINK_PARAM_TYPE_BOOL = DEVLINK_VAR_ATTR_TYPE_FLAG,
+	DEVLINK_PARAM_TYPE_U64_ARRAY = DEVLINK_VAR_ATTR_TYPE_U64_ARRAY,
+};
+
+#define __DEVLINK_PARAM_MAX_ARRAY_SIZE 32
+struct devlink_param_u64_array {
+	u64 size;
+	u64 val[__DEVLINK_PARAM_MAX_ARRAY_SIZE];
 };
 
 union devlink_param_value {
@@ -442,6 +449,7 @@ union devlink_param_value {
 	u64 vu64;
 	char vstr[__DEVLINK_PARAM_MAX_STRING_VALUE];
 	bool vbool;
+	struct devlink_param_u64_array u64arr;
 };
 
 struct devlink_param_gset_ctx {

include/uapi/linux/devlink.h

@@ -406,6 +406,7 @@ enum devlink_var_attr_type {
 	DEVLINK_VAR_ATTR_TYPE_BINARY,
 	__DEVLINK_VAR_ATTR_TYPE_CUSTOM_BASE = 0x80,
 	/* Any possible custom types, unrelated to NLA_* values go below */
+	DEVLINK_VAR_ATTR_TYPE_U64_ARRAY,
 };
 
 enum devlink_attr {

net/devlink/netlink_gen.c

@@ -37,6 +37,8 @@ devlink_attr_param_type_validate(const struct nlattr *attr,
 	case DEVLINK_VAR_ATTR_TYPE_NUL_STRING:
 		fallthrough;
 	case DEVLINK_VAR_ATTR_TYPE_BINARY:
+		fallthrough;
+	case DEVLINK_VAR_ATTR_TYPE_U64_ARRAY:
 		return 0;
 	}
 	NL_SET_ERR_MSG_ATTR(extack, attr, "invalid enum value");

net/devlink/param.c

@@ -252,6 +252,15 @@ devlink_nl_param_value_put(struct sk_buff *msg, enum devlink_param_type type,
 				return -EMSGSIZE;
 		}
 		break;
+	case DEVLINK_PARAM_TYPE_U64_ARRAY:
+		if (val->u64arr.size > __DEVLINK_PARAM_MAX_ARRAY_SIZE)
+			return -EMSGSIZE;
+
+		for (int i = 0; i < val->u64arr.size; i++) {
+			if (nla_put_uint(msg, nla_type, val->u64arr.val[i]))
+				return -EMSGSIZE;
+		}
+		break;
 	}
 	return 0;
 }
@@ -537,7 +546,7 @@ devlink_param_value_get_from_info(const struct devlink_param *param,
 				  union devlink_param_value *value)
 {
 	struct nlattr *param_data;
-	int len;
+	int len, cnt, rem;
 
 	param_data = info->attrs[DEVLINK_ATTR_PARAM_VALUE_DATA];
 
@@ -577,6 +586,28 @@ devlink_param_value_get_from_info(const struct devlink_param *param,
 			return -EINVAL;
 		value->vbool = nla_get_flag(param_data);
 		break;
+
+	case DEVLINK_PARAM_TYPE_U64_ARRAY:
+		cnt = 0;
+		nla_for_each_attr_type(param_data,
+				       DEVLINK_ATTR_PARAM_VALUE_DATA,
+				       genlmsg_data(info->genlhdr),
+				       genlmsg_len(info->genlhdr), rem) {
+			if (cnt >= __DEVLINK_PARAM_MAX_ARRAY_SIZE)
+				return -EMSGSIZE;
+
+			if ((nla_len(param_data) != sizeof(u64)) &&
+			    (nla_len(param_data) != sizeof(u32))) {
+				NL_SET_BAD_ATTR(info->extack, param_data);
+				return -EINVAL;
+			}
+
+			value->u64arr.val[cnt] = nla_get_uint(param_data);
+			cnt++;
+		}
+
+		value->u64arr.size = cnt;
+		break;
 	}
 	return 0;
 }