[PATCH] drm/drm_bridge: adjust bridge module's refcount

[Jyri Sarha <jsarha@xxxxxx>]

Store the module that provides the bridge and adjust its refcount
accordingly. The bridge module unload should not be allowed while the
bridge is attached.

Signed-off-by: Jyri Sarha <jsarha@xxxxxx>
---
 drivers/gpu/drm/drm_bridge.c | 15 ++++++++++++---
 include/drm/drm_bridge.h     | 11 ++++++++++-
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 0ee052b..36d427b 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -61,22 +61,26 @@
 static LIST_HEAD(bridge_list);
 
 /**
- * drm_bridge_add - add the given bridge to the global bridge list
+ * __drm_bridge_add - add the given bridge to the global bridge list
  *
  * @bridge: bridge control structure
+ * @module: module that provides this bridge
  *
  * RETURNS:
  * Unconditionally returns Zero.
  */
-int drm_bridge_add(struct drm_bridge *bridge)
+int __drm_bridge_add(struct drm_bridge *bridge, struct module *module)
 {
+#ifdef MODULE
+	bridge->module = module;
+#endif
 	mutex_lock(&bridge_lock);
 	list_add_tail(&bridge->list, &bridge_list);
 	mutex_unlock(&bridge_lock);
 
 	return 0;
 }
-EXPORT_SYMBOL(drm_bridge_add);
+EXPORT_SYMBOL(__drm_bridge_add);
 
 /**
  * drm_bridge_remove - remove the given bridge from the global bridge list
@@ -114,6 +118,9 @@ int drm_bridge_attach(struct drm_device *dev, struct drm_bridge *bridge)
 	if (bridge->dev)
 		return -EBUSY;
 
+	if (!try_module_get(bridge->module))
+		return -ENOENT;
+
 	bridge->dev = dev;
 
 	if (bridge->funcs->attach)
@@ -144,6 +151,8 @@ void drm_bridge_detach(struct drm_bridge *bridge)
 	if (bridge->funcs->detach)
 		bridge->funcs->detach(bridge);
 
+	module_put(bridge->module);
+
 	bridge->dev = NULL;
 }
 EXPORT_SYMBOL(drm_bridge_detach);
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 530a1d6..d60d5d2 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -25,6 +25,7 @@
 
 #include <linux/list.h>
 #include <linux/ctype.h>
+#include <linux/module.h>
 #include <drm/drm_mode_object.h>
 #include <drm/drm_modes.h>
 
@@ -192,13 +193,21 @@ struct drm_bridge {
 #ifdef CONFIG_OF
 	struct device_node *of_node;
 #endif
+#ifdef MODULE
+	struct module *module;
+#endif
 	struct list_head list;
 
 	const struct drm_bridge_funcs *funcs;
 	void *driver_private;
 };
 
-int drm_bridge_add(struct drm_bridge *bridge);
+int __drm_bridge_add(struct drm_bridge *bridge, struct module *module);
+#ifdef MODULE
+#define drm_bridge_add(bridge) __drm_bridge_add(bridge, THIS_MODULE)
+#else
+#define drm_bridge_add(bridge) __drm_bridge_add(bridge, NULL)
+#endif
 void drm_bridge_remove(struct drm_bridge *bridge);
 struct drm_bridge *of_drm_find_bridge(struct device_node *np);
 int drm_bridge_attach(struct drm_device *dev, struct drm_bridge *bridge);
-- 
1.9.1

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