mlxsw: spectrum_qdisc: Validate qdisc topology

A following patch will enable offloading qdiscs that are deeper than
directly under root qdisc. Currently the topology validation consists of
demanding a root qdisc position for ETS and PRIO. Since RED and TBF are
considered classless, this is enough. In order to prevent some nonsensical
combinations when RED and TBF become classful, introduce a more general
topology validator.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_qdisc.c

@@ -157,8 +157,7 @@ mlxsw_sp_qdisc_walk_cb_find(struct mlxsw_sp_qdisc *qdisc, void *data)
 }
 
 static struct mlxsw_sp_qdisc *
-mlxsw_sp_qdisc_find(struct mlxsw_sp_port *mlxsw_sp_port, u32 parent,
-		    bool root_only)
+mlxsw_sp_qdisc_find(struct mlxsw_sp_port *mlxsw_sp_port, u32 parent)
 {
 	struct mlxsw_sp_qdisc_state *qdisc_state = mlxsw_sp_port->qdisc;
 
@@ -166,8 +165,6 @@ mlxsw_sp_qdisc_find(struct mlxsw_sp_port *mlxsw_sp_port, u32 parent,
 		return NULL;
 	if (parent == TC_H_ROOT)
 		return &qdisc_state->root_qdisc;
-	if (root_only)
-		return NULL;
 	return mlxsw_sp_qdisc_walk(&qdisc_state->root_qdisc,
 				   mlxsw_sp_qdisc_walk_cb_find, &parent);
 }
@@ -268,6 +265,78 @@ mlxsw_sp_qdisc_destroy(struct mlxsw_sp_port *mlxsw_sp_port,
 	return err_hdroom ?: err;
 }
 
+struct mlxsw_sp_qdisc_tree_validate {
+	bool forbid_ets;
+	bool forbid_tbf;
+	bool forbid_red;
+};
+
+static int
+__mlxsw_sp_qdisc_tree_validate(struct mlxsw_sp_qdisc *mlxsw_sp_qdisc,
+			       struct mlxsw_sp_qdisc_tree_validate validate);
+
+static int
+mlxsw_sp_qdisc_tree_validate_children(struct mlxsw_sp_qdisc *mlxsw_sp_qdisc,
+				      struct mlxsw_sp_qdisc_tree_validate validate)
+{
+	unsigned int i;
+	int err;
+
+	for (i = 0; i < mlxsw_sp_qdisc->num_classes; i++) {
+		err = __mlxsw_sp_qdisc_tree_validate(&mlxsw_sp_qdisc->qdiscs[i],
+						     validate);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static int
+__mlxsw_sp_qdisc_tree_validate(struct mlxsw_sp_qdisc *mlxsw_sp_qdisc,
+			       struct mlxsw_sp_qdisc_tree_validate validate)
+{
+	if (!mlxsw_sp_qdisc->ops)
+		return 0;
+
+	switch (mlxsw_sp_qdisc->ops->type) {
+	case MLXSW_SP_QDISC_FIFO:
+		break;
+	case MLXSW_SP_QDISC_RED:
+		if (validate.forbid_red)
+			return -EINVAL;
+		validate.forbid_red = true;
+		validate.forbid_ets = true;
+		break;
+	case MLXSW_SP_QDISC_TBF:
+		if (validate.forbid_tbf)
+			return -EINVAL;
+		validate.forbid_tbf = true;
+		validate.forbid_ets = true;
+		break;
+	case MLXSW_SP_QDISC_PRIO:
+	case MLXSW_SP_QDISC_ETS:
+		if (validate.forbid_ets)
+			return -EINVAL;
+		validate.forbid_ets = true;
+		break;
+	default:
+		WARN_ON(1);
+		return -EINVAL;
+	}
+
+	return mlxsw_sp_qdisc_tree_validate_children(mlxsw_sp_qdisc, validate);
+}
+
+static int mlxsw_sp_qdisc_tree_validate(struct mlxsw_sp_port *mlxsw_sp_port)
+{
+	struct mlxsw_sp_qdisc_tree_validate validate = {};
+	struct mlxsw_sp_qdisc *mlxsw_sp_qdisc;
+
+	mlxsw_sp_qdisc = &mlxsw_sp_port->qdisc->root_qdisc;
+	return __mlxsw_sp_qdisc_tree_validate(mlxsw_sp_qdisc, validate);
+}
+
 static int mlxsw_sp_qdisc_create(struct mlxsw_sp_port *mlxsw_sp_port,
 				 u32 handle,
 				 struct mlxsw_sp_qdisc *mlxsw_sp_qdisc,
@@ -310,6 +379,10 @@ static int mlxsw_sp_qdisc_create(struct mlxsw_sp_port *mlxsw_sp_port,
 	mlxsw_sp_qdisc->num_classes = ops->num_classes;
 	mlxsw_sp_qdisc->ops = ops;
 	mlxsw_sp_qdisc->handle = handle;
+	err = mlxsw_sp_qdisc_tree_validate(mlxsw_sp_port);
+	if (err)
+		goto err_replace;
+
 	err = ops->replace(mlxsw_sp_port, handle, mlxsw_sp_qdisc, params);
 	if (err)
 		goto err_replace;
@@ -748,7 +821,7 @@ static int __mlxsw_sp_setup_tc_red(struct mlxsw_sp_port *mlxsw_sp_port,
 {
 	struct mlxsw_sp_qdisc *mlxsw_sp_qdisc;
 
-	mlxsw_sp_qdisc = mlxsw_sp_qdisc_find(mlxsw_sp_port, p->parent, false);
+	mlxsw_sp_qdisc = mlxsw_sp_qdisc_find(mlxsw_sp_port, p->parent);
 	if (!mlxsw_sp_qdisc)
 		return -EOPNOTSUPP;
 
@@ -964,7 +1037,7 @@ static int __mlxsw_sp_setup_tc_tbf(struct mlxsw_sp_port *mlxsw_sp_port,
 {
 	struct mlxsw_sp_qdisc *mlxsw_sp_qdisc;
 
-	mlxsw_sp_qdisc = mlxsw_sp_qdisc_find(mlxsw_sp_port, p->parent, false);
+	mlxsw_sp_qdisc = mlxsw_sp_qdisc_find(mlxsw_sp_port, p->parent);
 	if (!mlxsw_sp_qdisc)
 		return -EOPNOTSUPP;
 
@@ -1070,7 +1143,7 @@ static int __mlxsw_sp_setup_tc_fifo(struct mlxsw_sp_port *mlxsw_sp_port,
 	unsigned int band;
 	u32 parent_handle;
 
-	mlxsw_sp_qdisc = mlxsw_sp_qdisc_find(mlxsw_sp_port, p->parent, false);
+	mlxsw_sp_qdisc = mlxsw_sp_qdisc_find(mlxsw_sp_port, p->parent);
 	if (!mlxsw_sp_qdisc && p->handle == TC_H_UNSPEC) {
 		parent_handle = TC_H_MAJ(p->parent);
 		if (parent_handle != qdisc_state->future_handle) {
@@ -1534,7 +1607,7 @@ static int __mlxsw_sp_setup_tc_prio(struct mlxsw_sp_port *mlxsw_sp_port,
 {
 	struct mlxsw_sp_qdisc *mlxsw_sp_qdisc;
 
-	mlxsw_sp_qdisc = mlxsw_sp_qdisc_find(mlxsw_sp_port, p->parent, true);
+	mlxsw_sp_qdisc = mlxsw_sp_qdisc_find(mlxsw_sp_port, p->parent);
 	if (!mlxsw_sp_qdisc)
 		return -EOPNOTSUPP;
 
@@ -1579,7 +1652,7 @@ static int __mlxsw_sp_setup_tc_ets(struct mlxsw_sp_port *mlxsw_sp_port,
 {
 	struct mlxsw_sp_qdisc *mlxsw_sp_qdisc;
 
-	mlxsw_sp_qdisc = mlxsw_sp_qdisc_find(mlxsw_sp_port, p->parent, true);
+	mlxsw_sp_qdisc = mlxsw_sp_qdisc_find(mlxsw_sp_port, p->parent);
 	if (!mlxsw_sp_qdisc)
 		return -EOPNOTSUPP;