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| -rw-r--r-- | Documentation/video4linux/v4l2-framework.txt | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt index 1c8d4492f5c7..7d09114af00b 100644 --- a/Documentation/video4linux/v4l2-framework.txt +++ b/Documentation/video4linux/v4l2-framework.txt @@ -181,6 +181,21 @@ static int __devinit drv_probe(struct pci_dev *pdev, state->instance = atomic_inc_return(&drv_instance) - 1; } +If you have multiple device nodes then it can be difficult to know when it is +safe to unregister v4l2_device. For this purpose v4l2_device has refcounting +support. The refcount is increased whenever video_register_device is called and +it is decreased whenever that device node is released. When the refcount reaches +zero, then the v4l2_device release() callback is called. You can do your final +cleanup there. + +If other device nodes (e.g. ALSA) are created, then you can increase and +decrease the refcount manually as well by calling: + +void v4l2_device_get(struct v4l2_device *v4l2_dev); + +or: + +int v4l2_device_put(struct v4l2_device *v4l2_dev); struct v4l2_subdev ------------------ |