iommu: Add DOMAIN_ATTR_WINDOWS domain attribute

This attribute can be used to set and get the number of
subwindows on IOMMUs that are window-based.
Signed-off-by: Joerg Roedel <joro@8bytes.org>

drivers/iommu/iommu.c

@@ -891,6 +891,7 @@ int iommu_domain_get_attr(struct iommu_domain *domain,
 	struct iommu_domain_geometry *geometry;
 	bool *paging;
 	int ret = 0;
+	u32 *count;
 
 	switch (attr) {
 	case DOMAIN_ATTR_GEOMETRY:
@@ -901,6 +902,15 @@ int iommu_domain_get_attr(struct iommu_domain *domain,
 	case DOMAIN_ATTR_PAGING:
 		paging  = data;
 		*paging = (domain->ops->pgsize_bitmap != 0UL);
+		break;
+	case DOMAIN_ATTR_WINDOWS:
+		count = data;
+
+		if (domain->ops->domain_get_windows != NULL)
+			*count = domain->ops->domain_get_windows(domain);
+		else
+			ret = -ENODEV;
+
 		break;
 	default:
 		if (!domain->ops->domain_get_attr)
@@ -916,9 +926,26 @@ EXPORT_SYMBOL_GPL(iommu_domain_get_attr);
 int iommu_domain_set_attr(struct iommu_domain *domain,
 			  enum iommu_attr attr, void *data)
 {
-	if (!domain->ops->domain_set_attr)
-		return -EINVAL;
+	int ret = 0;
+	u32 *count;
+
+	switch (attr) {
+	case DOMAIN_ATTR_WINDOWS:
+		count = data;
+
+		if (domain->ops->domain_set_windows != NULL)
+			ret = domain->ops->domain_set_windows(domain, *count);
+		else
+			ret = -ENODEV;
 
-	return domain->ops->domain_set_attr(domain, attr, data);
+		break;
+	default:
+		if (domain->ops->domain_set_attr == NULL)
+			return -EINVAL;
+
+		ret = domain->ops->domain_set_attr(domain, attr, data);
+	}
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(iommu_domain_set_attr);

include/linux/iommu.h

@@ -60,6 +60,7 @@ struct iommu_domain {
 enum iommu_attr {
 	DOMAIN_ATTR_GEOMETRY,
 	DOMAIN_ATTR_PAGING,
+	DOMAIN_ATTR_WINDOWS,
 	DOMAIN_ATTR_MAX,
 };
 
@@ -106,6 +107,10 @@ struct iommu_ops {
 	int (*domain_window_enable)(struct iommu_domain *domain, u32 wnd_nr,
 				    phys_addr_t paddr, u64 size);
 	void (*domain_window_disable)(struct iommu_domain *domain, u32 wnd_nr);
+	/* Set the numer of window per domain */
+	int (*domain_set_windows)(struct iommu_domain *domain, u32 w_count);
+	/* Get the numer of window per domain */
+	u32 (*domain_get_windows)(struct iommu_domain *domain);
 
 	unsigned long pgsize_bitmap;
 };