[media] v4l: Only get module if it's different than the driver for v4l2_dev

When the sub-device is registered, increment the use count of the sub-device
owner only if it's different from the owner of the driver for the media
device. This avoids increasing the use count by the module itself and thus
making it possible to unload it when it's not in use.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

diff --git a/drivers/media/v4l2-core/v4l2-device.c b/drivers/media/v4l2-core/v4l2-device.c
index 02d1b6327117b4ba599bed35f56e9c89a6669943..015f92aab44a85b602c0ae58b3632fe7661015cf 100644 (file)
--- a/drivers/media/v4l2-core/v4l2-device.c
+++ b/drivers/media/v4l2-core/v4l2-device.c
@@ -158,7 +158,17 @@ int v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
        /* Warn if we apparently re-register a subdev */
        WARN_ON(sd->v4l2_dev != NULL);
 
-       if (!try_module_get(sd->owner))
+       /*
+        * The reason to acquire the module here is to avoid unloading
+        * a module of sub-device which is registered to a media
+        * device. To make it possible to unload modules for media
+        * devices that also register sub-devices, do not
+        * try_module_get() such sub-device owners.
+        */
+       sd->owner_v4l2_dev = v4l2_dev->dev && v4l2_dev->dev->driver &&
+               sd->owner == v4l2_dev->dev->driver->owner;
+
+       if (!sd->owner_v4l2_dev && !try_module_get(sd->owner))
                return -ENODEV;
 
        sd->v4l2_dev = v4l2_dev;
@@ -192,7 +202,8 @@ error_unregister:
        if (sd->internal_ops && sd->internal_ops->unregistered)
                sd->internal_ops->unregistered(sd);
 error_module:
-       module_put(sd->owner);
+       if (!sd->owner_v4l2_dev)
+               module_put(sd->owner);
        sd->v4l2_dev = NULL;
        return err;
 }
@@ -280,6 +291,7 @@ void v4l2_device_unregister_subdev(struct v4l2_subdev *sd)
        }
 #endif
        video_unregister_device(sd->devnode);
-       module_put(sd->owner);
+       if (!sd->owner_v4l2_dev)
+               module_put(sd->owner);
 }
 EXPORT_SYMBOL_GPL(v4l2_device_unregister_subdev);

diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index ee1cb2d354a8a21f8e1bd860b180e8fb1e93ded9..ee0ae769ca9427cd1f0e5a36be2d341c60adbc4f 100644 (file)
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -584,6 +584,7 @@ struct v4l2_subdev {
 #endif
        struct list_head list;
        struct module *owner;
+       bool owner_v4l2_dev;
        u32 flags;
        struct v4l2_device *v4l2_dev;
        const struct v4l2_subdev_ops *ops;