[media] v4l: subdev: Add device node support

Create a device node named subdevX for every registered subdev.

As the device node is registered before the subdev core::s_config
function is called, return -EGAIN on open until initialization
completes.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Vimarsh Zutshi <vimarsh.zutshi@gmail.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/drivers/media/video/v4l2-device.c b/drivers/media/video/v4l2-device.c
index ce64fe16bc60..8c0ad8b372d8 100644
--- a/drivers/media/video/v4l2-device.c
+++ b/drivers/media/video/v4l2-device.c
@@ -124,16 +124,20 @@ int v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
         /* Check for valid input */
         if (v4l2_dev == NULL || sd == NULL || !sd->name[0])
                 return -EINVAL;
+
         /* Warn if we apparently re-register a subdev */
         WARN_ON(sd->v4l2_dev != NULL);
+
         if (!try_module_get(sd->owner))
                 return -ENODEV;
+
         sd->v4l2_dev = v4l2_dev;
         if (sd->internal_ops && sd->internal_ops->registered) {
                 err = sd->internal_ops->registered(sd);
                 if (err)
                         return err;
         }
+
         /* This just returns 0 if either of the two args is NULL */
         err = v4l2_ctrl_add_handler(v4l2_dev->ctrl_handler, sd->ctrl_handler);
         if (err) {
@@ -141,24 +145,57 @@ int v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
                         sd->internal_ops->unregistered(sd);
                 return err;
         }
+
         spin_lock(&v4l2_dev->lock);
         list_add_tail(&sd->list, &v4l2_dev->subdevs);
         spin_unlock(&v4l2_dev->lock);
+
         return 0;
 }
 EXPORT_SYMBOL_GPL(v4l2_device_register_subdev);
 
+int v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
+{
+        struct video_device *vdev;
+        struct v4l2_subdev *sd;
+        int err;
+
+        /* Register a device node for every subdev marked with the
+         * V4L2_SUBDEV_FL_HAS_DEVNODE flag.
+         */
+        list_for_each_entry(sd, &v4l2_dev->subdevs, list) {
+                if (!(sd->flags & V4L2_SUBDEV_FL_HAS_DEVNODE))
+                        continue;
+
+                vdev = &sd->devnode;
+                strlcpy(vdev->name, sd->name, sizeof(vdev->name));
+                vdev->v4l2_dev = v4l2_dev;
+                vdev->fops = &v4l2_subdev_fops;
+                vdev->release = video_device_release_empty;
+                err = __video_register_device(vdev, VFL_TYPE_SUBDEV, -1, 1,
+                                              sd->owner);
+                if (err < 0)
+                        return err;
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_device_register_subdev_nodes);
+
 void v4l2_device_unregister_subdev(struct v4l2_subdev *sd)
 {
         /* return if it isn't registered */
         if (sd == NULL || sd->v4l2_dev == NULL)
                 return;
+
         spin_lock(&sd->v4l2_dev->lock);
         list_del(&sd->list);
         spin_unlock(&sd->v4l2_dev->lock);
         if (sd->internal_ops && sd->internal_ops->unregistered)
                 sd->internal_ops->unregistered(sd);
         sd->v4l2_dev = NULL;
+
+        video_unregister_device(&sd->devnode);
         module_put(sd->owner);
 }
 EXPORT_SYMBOL_GPL(v4l2_device_unregister_subdev);