iommu: Add find group by name function

Provide an abstraction for IOMMU clients by decoupling clients
from actual IOMMU devices by allowing clients to find an IOMMU
group based on its name.

Change-Id: I89702cc761113197b6fd58c3372fd47f9b00bfaa
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>

drivers/iommu/iommu.c

@@ -32,7 +32,7 @@
 #include <linux/err.h>
 
 static struct kset *iommu_group_kset;
-static struct ida iommu_group_ida;
+static struct idr iommu_group_idr;
 static struct mutex iommu_group_mutex;
 
 struct iommu_group {
@@ -126,7 +126,7 @@ static void iommu_group_release(struct kobject *kobj)
 		group->iommu_data_release(group->iommu_data);
 
 	mutex_lock(&iommu_group_mutex);
-	ida_remove(&iommu_group_ida, group->id);
+	idr_remove(&iommu_group_idr, group->id);
 	mutex_unlock(&iommu_group_mutex);
 
 	kfree(group->name);
@@ -167,22 +167,27 @@ struct iommu_group *iommu_group_alloc(void)
 	mutex_lock(&iommu_group_mutex);
 
 again:
-	if (unlikely(0 == ida_pre_get(&iommu_group_ida, GFP_KERNEL))) {
+	if (unlikely(0 == idr_pre_get(&iommu_group_idr, GFP_KERNEL))) {
 		kfree(group);
 		mutex_unlock(&iommu_group_mutex);
 		return ERR_PTR(-ENOMEM);
 	}
 
-	if (-EAGAIN == ida_get_new(&iommu_group_ida, &group->id))
+	ret = idr_get_new_above(&iommu_group_idr, group, 1, &group->id);
+	if (ret == -EAGAIN)
 		goto again;
-
 	mutex_unlock(&iommu_group_mutex);
 
+	if (ret == -ENOSPC) {
+		kfree(group);
+		return ERR_PTR(ret);
+	}
+
 	ret = kobject_init_and_add(&group->kobj, &iommu_group_ktype,
 				   NULL, "%d", group->id);
 	if (ret) {
 		mutex_lock(&iommu_group_mutex);
-		ida_remove(&iommu_group_ida, group->id);
+		idr_remove(&iommu_group_idr, group->id);
 		mutex_unlock(&iommu_group_mutex);
 		kfree(group);
 		return ERR_PTR(ret);
@@ -425,6 +430,37 @@ struct iommu_group *iommu_group_get(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(iommu_group_get);
 
+/**
+ * iommu_group_find - Find and return the group based on the group name.
+ * Also increment the reference count.
+ * @name: the name of the group
+ *
+ * This function is called by iommu drivers and clients to get the group
+ * by the specified name.  If found, the group is returned and the group
+ * reference is incremented, else NULL.
+ */
+struct iommu_group *iommu_group_find(const char *name)
+{
+	struct iommu_group *group;
+	int next = 0;
+
+	mutex_lock(&iommu_group_mutex);
+	while ((group = idr_get_next(&iommu_group_idr, &next))) {
+		if (group->name) {
+			if (strcmp(group->name, name) == 0)
+				break;
+		}
+		++next;
+	}
+	mutex_unlock(&iommu_group_mutex);
+
+	if (group)
+		kobject_get(group->devices_kobj);
+
+	return group;
+}
+EXPORT_SYMBOL_GPL(iommu_group_find);
+
 /**
  * iommu_group_put - Decrement group reference
  * @group: the group to use
@@ -888,7 +924,7 @@ static int __init iommu_init(void)
 {
 	iommu_group_kset = kset_create_and_add("iommu_groups",
 					       NULL, kernel_kobj);
-	ida_init(&iommu_group_ida);
+	idr_init(&iommu_group_idr);
 	mutex_init(&iommu_group_mutex);
 
 	BUG_ON(!iommu_group_kset);

include/linux/iommu.h

@@ -138,6 +138,7 @@ extern void iommu_group_remove_device(struct device *dev);
 extern int iommu_group_for_each_dev(struct iommu_group *group, void *data,
 				    int (*fn)(struct device *, void *));
 extern struct iommu_group *iommu_group_get(struct device *dev);
+extern struct iommu_group *iommu_group_find(const char *name);
 extern void iommu_group_put(struct iommu_group *group);
 extern int iommu_group_register_notifier(struct iommu_group *group,
 					 struct notifier_block *nb);
@@ -317,6 +318,11 @@ static inline struct iommu_group *iommu_group_get(struct device *dev)
 	return NULL;
 }
 
+static inline struct iommu_group *iommu_group_find(const char *name)
+{
+	return NULL;
+}
+
 static inline void iommu_group_put(struct iommu_group *group)
 {
 }