source/iommu: deprecate and disable by default

Deprecate the iommu source and disable it by default.

docs/get-started/features.md

@@ -428,14 +428,16 @@ labels by defining them in the `nfd-worker` configuration file.
 | rdma  | capable | The node has an RDMA capable Network adapter |
 | rdma | enabled | The node has the needed RDMA modules loaded to run RDMA traffic |
 
-### IOMMU
+### IOMMU (deprecated)
 
 The **iommu** feature source supports the following labels:
 
 | Feature name   | Description                                                 |
 | :------------: | :---------------------------------------------------------: |
 | enabled        | IOMMU is present and enabled in the kernel
 
+**DEPRECATED**: The **iommu** source is deprecated and not enabled by default.
+
 ### Kernel
 
 The **kernel** feature source supports the following labels:

docs/get-started/introduction.md

@@ -52,7 +52,6 @@ supposed to be running on each node of the cluster.
 Feature discovery is divided into domain-specific feature sources:
 
 - CPU
-- IOMMU
 - Kernel
 - Memory
 - Network
@@ -62,6 +61,7 @@ Feature discovery is divided into domain-specific feature sources:
 - USB
 - Custom (rule-based custom features)
 - Local (hooks for user-specific features)
+- IOMMU (*deprecated*)
 
 Each feature source is responsible for detecting a set of features which. in
 turn, are turned into node feature labels.  Feature labels are prefixed with
@@ -75,7 +75,6 @@ An overview of the default feature labels:
 {
   "feature.node.kubernetes.io/cpu-<feature-name>": "true",
   "feature.node.kubernetes.io/custom-<feature-name>": "true",
-  "feature.node.kubernetes.io/iommu-<feature-name>": "true",
   "feature.node.kubernetes.io/kernel-<feature name>": "<feature value>",
   "feature.node.kubernetes.io/memory-<feature-name>": "true",
   "feature.node.kubernetes.io/network-<feature-name>": "true",

source/iommu/iommu.go

@@ -56,6 +56,9 @@ func (s *iommuSource) GetLabels() (source.FeatureLabels, error) {
 	return features, nil
 }
 
+// DisableByDefault method of the SupplementalSource interface.
+func (s *iommuSource) DisableByDefault() bool { return true }
+
 func init() {
 	source.Register(&src)
 }