1 files changed, 54 insertions, 15 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 8c7327d45406..9d49b461b1d9 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -192,10 +192,21 @@ static void device_link_rpm_prepare(struct device *consumer,
  * of the link.  If DL_FLAG_PM_RUNTIME is not set, DL_FLAG_RPM_ACTIVE will be
  * ignored.
  *
- * If the DL_FLAG_AUTOREMOVE_CONSUMER flag is set, the link will be removed
- * automatically when the consumer device driver unbinds from it.  Analogously,
- * if DL_FLAG_AUTOREMOVE_SUPPLIER is set in @flags, the link will be removed
- * automatically when the supplier device driver unbinds from it.
+ * If DL_FLAG_STATELESS is set in @flags, the link is not going to be managed by
+ * the driver core and, in particular, the caller of this function is expected
+ * to drop the reference to the link acquired by it directly.
+ *
+ * If that flag is not set, however, the caller of this function is handing the
+ * management of the link over to the driver core entirely and its return value
+ * can only be used to check whether or not the link is present.  In that case,
+ * the DL_FLAG_AUTOREMOVE_CONSUMER and DL_FLAG_AUTOREMOVE_SUPPLIER device link
+ * flags can be used to indicate to the driver core when the link can be safely
+ * deleted.  Namely, setting one of them in @flags indicates to the driver core
+ * that the link is not going to be used (by the given caller of this function)
+ * after unbinding the consumer or supplier driver, respectively, from its
+ * device, so the link can be deleted at that point.  If none of them is set,
+ * the link will be maintained until one of the devices pointed to by it (either
+ * the consumer or the supplier) is unregistered.
  *
  * The combination of DL_FLAG_STATELESS and either DL_FLAG_AUTOREMOVE_CONSUMER
  * or DL_FLAG_AUTOREMOVE_SUPPLIER set in @flags at the same time is invalid and
@@ -241,6 +252,14 @@ struct device_link *device_link_add(struct device *consumer,
                 goto out;
         }
 
+        /*
+         * DL_FLAG_AUTOREMOVE_SUPPLIER indicates that the link will be needed
+         * longer than for DL_FLAG_AUTOREMOVE_CONSUMER and setting them both
+         * together doesn't make sense, so prefer DL_FLAG_AUTOREMOVE_SUPPLIER.
+         */
+        if (flags & DL_FLAG_AUTOREMOVE_SUPPLIER)
+                flags &= ~DL_FLAG_AUTOREMOVE_CONSUMER;
+
         list_for_each_entry(link, &supplier->links.consumers, s_node) {
                 if (link->consumer != consumer)
                         continue;
@@ -254,12 +273,6 @@ struct device_link *device_link_add(struct device *consumer,
                         goto out;
                 }
 
-                if (flags & DL_FLAG_AUTOREMOVE_CONSUMER)
-                        link->flags |= DL_FLAG_AUTOREMOVE_CONSUMER;
-
-                if (flags & DL_FLAG_AUTOREMOVE_SUPPLIER)
-                        link->flags |= DL_FLAG_AUTOREMOVE_SUPPLIER;
-
                 if (flags & DL_FLAG_PM_RUNTIME) {
                         if (!(link->flags & DL_FLAG_PM_RUNTIME)) {
                                 device_link_rpm_prepare(consumer, supplier);
@@ -269,7 +282,25 @@ struct device_link *device_link_add(struct device *consumer,
                                 refcount_inc(&link->rpm_active);
                 }
 
-                kref_get(&link->kref);
+                if (flags & DL_FLAG_STATELESS) {
+                        kref_get(&link->kref);
+                        goto out;
+                }
+
+                /*
+                 * If the life time of the link following from the new flags is
+                 * longer than indicated by the flags of the existing link,
+                 * update the existing link to stay around longer.
+                 */
+                if (flags & DL_FLAG_AUTOREMOVE_SUPPLIER) {
+                        if (link->flags & DL_FLAG_AUTOREMOVE_CONSUMER) {
+                                link->flags &= ~DL_FLAG_AUTOREMOVE_CONSUMER;
+                                link->flags |= DL_FLAG_AUTOREMOVE_SUPPLIER;
+                        }
+                } else if (!(flags & DL_FLAG_AUTOREMOVE_CONSUMER)) {
+                        link->flags &= ~(DL_FLAG_AUTOREMOVE_CONSUMER |
+                                         DL_FLAG_AUTOREMOVE_SUPPLIER);
+                }
                 goto out;
         }
 
@@ -419,8 +450,16 @@ static void __device_link_del(struct kref *kref)
 }
 #endif /* !CONFIG_SRCU */
 
+static void device_link_put_kref(struct device_link *link)
+{
+        if (link->flags & DL_FLAG_STATELESS)
+                kref_put(&link->kref, __device_link_del);
+        else
+                WARN(1, "Unable to drop a managed device link reference\n");
+}
+
 /**
- * device_link_del - Delete a link between two devices.
+ * device_link_del - Delete a stateless link between two devices.
  * @link: Device link to delete.
  *
  * The caller must ensure proper synchronization of this function with runtime
@@ -432,14 +471,14 @@ void device_link_del(struct device_link *link)
 {
         device_links_write_lock();
         device_pm_lock();
-        kref_put(&link->kref, __device_link_del);
+        device_link_put_kref(link);
         device_pm_unlock();
         device_links_write_unlock();
 }
 EXPORT_SYMBOL_GPL(device_link_del);
 
 /**
- * device_link_remove - remove a link between two devices.
+ * device_link_remove - Delete a stateless link between two devices.
  * @consumer: Consumer end of the link.
  * @supplier: Supplier end of the link.
  *
@@ -458,7 +497,7 @@ void device_link_remove(void *consumer, struct device *supplier)
 
         list_for_each_entry(link, &supplier->links.consumers, s_node) {
                 if (link->consumer == consumer) {
-                        kref_put(&link->kref, __device_link_del);
+                        device_link_put_kref(link);
                         break;
                 }
         }