fpga manager: ensure lifetime with of_fpga_mgr_get

Ensure device and driver lifetime from of_fpga_mgr_get() to
fpga_mgr_put().

* Don't put_device() in of_fpga_mgr_get, do it in fpga_mgr_put().
  (still do put_device if there is an error).
* Do module_get on the low level driver.
* Don't need to module_get(THIS_MODULE) since we won't be allowed
  to unload the fpga manager core without unloading low level
  driver first.
* Remove unnedessary null check for node pointer.

Signed-off-by: Alan Tull <atull@opensource.altera.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 17 insertions, 15 deletions

diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
index 25261636687c..68d7b41159cb 100644
--- a/drivers/fpga/fpga-mgr.c
+++ b/drivers/fpga/fpga-mgr.c
@@ -204,9 +204,7 @@ struct fpga_manager *of_fpga_mgr_get(struct device_node *node)
 {
         struct fpga_manager *mgr;
         struct device *dev;
-
-        if (!node)
-                return ERR_PTR(-EINVAL);
+        int ret = -ENODEV;
 
         dev = class_find_device(fpga_mgr_class, NULL, node,
                                 fpga_mgr_of_node_match);
@@ -214,20 +212,25 @@ struct fpga_manager *of_fpga_mgr_get(struct device_node *node)
                 return ERR_PTR(-ENODEV);
 
         mgr = to_fpga_manager(dev);
-        put_device(dev);
         if (!mgr)
-                return ERR_PTR(-ENODEV);
+                goto err_dev;
 
         /* Get exclusive use of fpga manager */
-        if (!mutex_trylock(&mgr->ref_mutex))
-                return ERR_PTR(-EBUSY);
-
-        if (!try_module_get(THIS_MODULE)) {
-                mutex_unlock(&mgr->ref_mutex);
-                return ERR_PTR(-ENODEV);
+        if (!mutex_trylock(&mgr->ref_mutex)) {
+                ret = -EBUSY;
+                goto err_dev;
         }
 
+        if (!try_module_get(dev->parent->driver->owner))
+                goto err_ll_mod;
+
         return mgr;
+
+err_ll_mod:
+        mutex_unlock(&mgr->ref_mutex);
+err_dev:
+        put_device(dev);
+        return ERR_PTR(ret);
 }
 EXPORT_SYMBOL_GPL(of_fpga_mgr_get);
 
@@ -237,10 +240,9 @@ EXPORT_SYMBOL_GPL(of_fpga_mgr_get);
  */
 void fpga_mgr_put(struct fpga_manager *mgr)
 {
-        if (mgr) {
-                module_put(THIS_MODULE);
-                mutex_unlock(&mgr->ref_mutex);
-        }
+        module_put(mgr->dev.parent->driver->owner);
+        mutex_unlock(&mgr->ref_mutex);
+        put_device(&mgr->dev);
 }
 EXPORT_SYMBOL_GPL(fpga_mgr_put);