[PATCH v2] V4L: dynamically allocate video_device nodes in subdevices

[Guennadi Liakhovetski <g.liakhovetski@xxxxxx>]

Currently only very few drivers actually use video_device nodes, embedded
in struct v4l2_subdev. Allocate these nodes dynamically for those drivers
to save memory for the rest.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
---

v2: Checking for NULL is not always enough, you also have to check the 
right thing for it. In this case it was sd->devnode in 
v4l2_device_unregister_subdev().

 drivers/media/video/v4l2-device.c |   29 ++++++++++++++++++++++++++---
 include/media/v4l2-subdev.h       |   10 ++++++++--
 2 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/drivers/media/video/v4l2-device.c b/drivers/media/video/v4l2-device.c
index c72856c..d4c093f 100644
--- a/drivers/media/video/v4l2-device.c
+++ b/drivers/media/video/v4l2-device.c
@@ -21,6 +21,7 @@
 #include <linux/types.h>
 #include <linux/ioctl.h>
 #include <linux/i2c.h>
+#include <linux/slab.h>
 #if defined(CONFIG_SPI)
 #include <linux/spi/spi.h>
 #endif
@@ -194,6 +195,7 @@ EXPORT_SYMBOL_GPL(v4l2_device_register_subdev);
 int v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
 {
 	struct video_device *vdev;
+	struct v4l2_devnode *node;
 	struct v4l2_subdev *sd;
 	int err;
 
@@ -204,7 +206,13 @@ int v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
 		if (!(sd->flags & V4L2_SUBDEV_FL_HAS_DEVNODE))
 			continue;
 
-		vdev = &sd->devnode;
+		node = kzalloc(sizeof(*node), GFP_KERNEL);
+		if (!node) {
+			err = -ENOMEM;
+			goto clean_up;
+		}
+		vdev = &node->vdev;
+
 		strlcpy(vdev->name, sd->name, sizeof(vdev->name));
 		vdev->v4l2_dev = v4l2_dev;
 		vdev->fops = &v4l2_subdev_fops;
@@ -213,13 +221,25 @@ int v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
 		err = __video_register_device(vdev, VFL_TYPE_SUBDEV, -1, 1,
 					      sd->owner);
 		if (err < 0)
-			return err;
+			goto clean_up;
 #if defined(CONFIG_MEDIA_CONTROLLER)
 		sd->entity.v4l.major = VIDEO_MAJOR;
 		sd->entity.v4l.minor = vdev->minor;
 #endif
+		sd->devnode = node;
 	}
 	return 0;
+
+clean_up:
+	list_for_each_entry(sd, &v4l2_dev->subdevs, list) {
+		if (!sd->devnode)
+			break;
+		video_unregister_device(&sd->devnode->vdev);
+		kfree(sd->devnode);
+		sd->devnode = NULL;
+	}
+
+	return err;
 }
 EXPORT_SYMBOL_GPL(v4l2_device_register_subdev_nodes);
 
@@ -245,7 +265,10 @@ void v4l2_device_unregister_subdev(struct v4l2_subdev *sd)
 	if (v4l2_dev->mdev)
 		media_device_unregister_entity(&sd->entity);
 #endif
-	video_unregister_device(&sd->devnode);
+	if (sd->devnode)
+		video_unregister_device(&sd->devnode->vdev);
+	kfree(sd->devnode);
+	sd->devnode = NULL;
 	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 257da1a..6e958df 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -510,6 +510,12 @@ struct v4l2_subdev_internal_ops {
 /* Set this flag if this subdev generates events. */
 #define V4L2_SUBDEV_FL_HAS_EVENTS		(1U << 3)
 
+/* video_device with a reverse lookup */
+struct v4l2_devnode {
+	struct v4l2_subdev *sd;
+	struct video_device vdev;
+};
+
 /* Each instance of a subdev driver should create this struct, either
    stand-alone or embedded in a larger struct.
  */
@@ -534,13 +540,13 @@ struct v4l2_subdev {
 	void *dev_priv;
 	void *host_priv;
 	/* subdev device node */
-	struct video_device devnode;
+	struct v4l2_devnode *devnode;
 };
 
 #define media_entity_to_v4l2_subdev(ent) \
 	container_of(ent, struct v4l2_subdev, entity)
 #define vdev_to_v4l2_subdev(vdev) \
-	container_of(vdev, struct v4l2_subdev, devnode)
+	(container_of(vdev, struct v4l2_devnode, vdev)->sd)
 
 /*
  * Used for storing subdev information per file handle
-- 
1.7.2.5

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