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authorHans Verkuil <hverkuil@xs4all.nl>2011-02-24 06:28:46 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2011-03-22 16:38:06 -0300
commit2335e2b817186cf79a07311f14560ef8b30f6a9a (patch)
treec75b6d5f12c41734c01310409f7f26cfe65ee3dc /Documentation
parentbedf8bcf6b4f90a6e31add3721a2e71877289381 (diff)
downloadop-kernel-dev-2335e2b817186cf79a07311f14560ef8b30f6a9a.zip
op-kernel-dev-2335e2b817186cf79a07311f14560ef8b30f6a9a.tar.gz
[media] v4l2-framework.txt: document new v4l2_device release() callback
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/video4linux/v4l2-framework.txt15
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt
index 1c8d449..7d09114 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
------------------
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