iommu: Add dummy dev_iommu_fwspec_get() helper

This dummy implementation is useful to avoid a dependency on the
IOMMU_API Kconfig symbol in drivers that can optionally use the IOMMU
API.

In order to fully use this, also move the struct iommu_fwspec definition
out of the IOMMU_API protected region.

Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
Changes in v3:
- remove duplicate struct iommu_fwspec definition

include/linux/iommu.h

@@ -164,6 +164,28 @@ enum iommu_dev_features {
 
 #define IOMMU_PASID_INVALID	(-1U)
 
+/**
+ * struct iommu_fwspec - per-device IOMMU instance data
+ * @ops: ops for this device's IOMMU
+ * @iommu_fwnode: firmware handle for this device's IOMMU
+ * @iommu_priv: IOMMU driver private data for this device
+ * @flags: IOMMU flags associated with this device
+ * @num_pasid_bits: number of PASID bits supported by this device
+ * @num_ids: number of associated device IDs
+ * @ids: IDs which this device may present to the IOMMU
+ */
+struct iommu_fwspec {
+	const struct iommu_ops	*ops;
+	struct fwnode_handle	*iommu_fwnode;
+	u32			flags;
+	u32			num_pasid_bits;
+	unsigned int		num_ids;
+	u32			ids[];
+};
+
+/* ATS is supported */
+#define IOMMU_FWSPEC_PCI_RC_ATS			(1 << 0)
+
 #ifdef CONFIG_IOMMU_API
 
 /**
@@ -567,28 +589,6 @@ extern struct iommu_group *generic_device_group(struct device *dev);
 /* FSL-MC device grouping function */
 struct iommu_group *fsl_mc_device_group(struct device *dev);
 
-/**
- * struct iommu_fwspec - per-device IOMMU instance data
- * @ops: ops for this device's IOMMU
- * @iommu_fwnode: firmware handle for this device's IOMMU
- * @iommu_priv: IOMMU driver private data for this device
- * @flags: IOMMU flags associated with this device
- * @num_pasid_bits: number of PASID bits supported by this device
- * @num_ids: number of associated device IDs
- * @ids: IDs which this device may present to the IOMMU
- */
-struct iommu_fwspec {
-	const struct iommu_ops	*ops;
-	struct fwnode_handle	*iommu_fwnode;
-	u32			flags;
-	u32			num_pasid_bits;
-	unsigned int		num_ids;
-	u32			ids[];
-};
-
-/* ATS is supported */
-#define IOMMU_FWSPEC_PCI_RC_ATS			(1 << 0)
-
 /**
  * struct iommu_sva - handle to a device-mm bond
  */
@@ -649,7 +649,6 @@ u32 iommu_sva_get_pasid(struct iommu_sva *handle);
 
 struct iommu_ops {};
 struct iommu_group {};
-struct iommu_fwspec {};
 struct iommu_device {};
 struct iommu_fault_param {};
 struct iommu_iotlb_gather {};
@@ -980,6 +979,11 @@ const struct iommu_ops *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
 	return NULL;
 }
 
+static inline struct iommu_fwspec *dev_iommu_fwspec_get(struct device *dev)
+{
+	return NULL;
+}
+
 static inline bool
 iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features feat)
 {