iommu/vt-d: Refactor device_to_iommu() helper

It is refactored in two ways:

- Make it global so that it could be used in other files.

- Make bus/devfn optional so that callers could ignore these two returned
values when they only want to get the coresponding iommu pointer.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20200724014925.15523-9-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel/iommu.c

@@ -778,16 +778,16 @@ is_downstream_to_pci_bridge(struct device *dev, struct device *bridge)
 	return false;
 }
 
-static struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
+struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
 {
 	struct dmar_drhd_unit *drhd = NULL;
+	struct pci_dev *pdev = NULL;
 	struct intel_iommu *iommu;
 	struct device *tmp;
-	struct pci_dev *pdev = NULL;
 	u16 segment = 0;
 	int i;
 
-	if (iommu_dummy(dev))
+	if (!dev || iommu_dummy(dev))
 		return NULL;
 
 	if (dev_is_pci(dev)) {
@@ -818,8 +818,10 @@ static struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devf
 				if (pdev && pdev->is_virtfn)
 					goto got_pdev;
 
-				*bus = drhd->devices[i].bus;
-				*devfn = drhd->devices[i].devfn;
+				if (bus && devfn) {
+					*bus = drhd->devices[i].bus;
+					*devfn = drhd->devices[i].devfn;
+				}
 				goto out;
 			}
 
@@ -829,8 +831,10 @@ static struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devf
 
 		if (pdev && drhd->include_all) {
 		got_pdev:
-			*bus = pdev->bus->number;
-			*devfn = pdev->devfn;
+			if (bus && devfn) {
+				*bus = pdev->bus->number;
+				*devfn = pdev->devfn;
+			}
 			goto out;
 		}
 	}
@@ -5146,11 +5150,10 @@ static int aux_domain_add_dev(struct dmar_domain *domain,
 			      struct device *dev)
 {
 	int ret;
-	u8 bus, devfn;
 	unsigned long flags;
 	struct intel_iommu *iommu;
 
-	iommu = device_to_iommu(dev, &bus, &devfn);
+	iommu = device_to_iommu(dev, NULL, NULL);
 	if (!iommu)
 		return -ENODEV;
 
@@ -5236,9 +5239,8 @@ static int prepare_domain_attach_device(struct iommu_domain *domain,
 	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
 	struct intel_iommu *iommu;
 	int addr_width;
-	u8 bus, devfn;
 
-	iommu = device_to_iommu(dev, &bus, &devfn);
+	iommu = device_to_iommu(dev, NULL, NULL);
 	if (!iommu)
 		return -ENODEV;
 
@@ -5668,9 +5670,8 @@ static bool intel_iommu_capable(enum iommu_cap cap)
 static struct iommu_device *intel_iommu_probe_device(struct device *dev)
 {
 	struct intel_iommu *iommu;
-	u8 bus, devfn;
 
-	iommu = device_to_iommu(dev, &bus, &devfn);
+	iommu = device_to_iommu(dev, NULL, NULL);
 	if (!iommu)
 		return ERR_PTR(-ENODEV);
 
@@ -5683,9 +5684,8 @@ static struct iommu_device *intel_iommu_probe_device(struct device *dev)
 static void intel_iommu_release_device(struct device *dev)
 {
 	struct intel_iommu *iommu;
-	u8 bus, devfn;
 
-	iommu = device_to_iommu(dev, &bus, &devfn);
+	iommu = device_to_iommu(dev, NULL, NULL);
 	if (!iommu)
 		return;
 
@@ -5835,37 +5835,14 @@ static struct iommu_group *intel_iommu_device_group(struct device *dev)
 	return generic_device_group(dev);
 }
 
-#ifdef CONFIG_INTEL_IOMMU_SVM
-struct intel_iommu *intel_svm_device_to_iommu(struct device *dev)
-{
-	struct intel_iommu *iommu;
-	u8 bus, devfn;
-
-	if (iommu_dummy(dev)) {
-		dev_warn(dev,
-			 "No IOMMU translation for device; cannot enable SVM\n");
-		return NULL;
-	}
-
-	iommu = device_to_iommu(dev, &bus, &devfn);
-	if ((!iommu)) {
-		dev_err(dev, "No IOMMU for device; cannot enable SVM\n");
-		return NULL;
-	}
-
-	return iommu;
-}
-#endif /* CONFIG_INTEL_IOMMU_SVM */
-
 static int intel_iommu_enable_auxd(struct device *dev)
 {
 	struct device_domain_info *info;
 	struct intel_iommu *iommu;
 	unsigned long flags;
-	u8 bus, devfn;
 	int ret;
 
-	iommu = device_to_iommu(dev, &bus, &devfn);
+	iommu = device_to_iommu(dev, NULL, NULL);
 	if (!iommu || dmar_disabled)
 		return -EINVAL;