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authorHans Verkuil <hverkuil@xs4all.nl>2009-03-08 17:02:10 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2009-03-30 12:43:20 -0300
commit98ec633972a70cf71d71bc8762804f0af4792d08 (patch)
tree8f924a6d5804b56a24a58a1e60ea69d53996ece7 /Documentation/video4linux
parent005759613b95264fba9138010f112bc138c857c2 (diff)
V4L/DVB (11021): v4l2-device: add a notify callback.
Add a notify callback to v4l2_device to let sub-devices notify their parent of special events. Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'Documentation/video4linux')
-rw-r--r--Documentation/video4linux/v4l2-framework.txt10
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt
index df0247ed13d..4207590b2ac 100644
--- a/Documentation/video4linux/v4l2-framework.txt
+++ b/Documentation/video4linux/v4l2-framework.txt
@@ -94,6 +94,11 @@ usb_device or platform_device. It is rare for dev to be NULL, but it happens
with ISA devices or when one device creates multiple PCI devices, thus making
it impossible to associate v4l2_dev with a particular parent.
+You can also supply a notify() callback that can be called by sub-devices to
+notify you of events. Whether you need to set this depends on the sub-device.
+Any notifications a sub-device supports must be defined in a header in
+include/media/<subdevice>.h.
+
You unregister with:
v4l2_device_unregister(struct v4l2_device *v4l2_dev);
@@ -281,6 +286,11 @@ e.g. AUDIO_CONTROLLER and specify that as the group ID value when calling
v4l2_device_call_all(). That ensures that it will only go to the subdev
that needs it.
+If the sub-device needs to notify its v4l2_device parent of an event, then
+it can call v4l2_subdev_notify(sd, notification, arg). This macro checks
+whether there is a notify() callback defined and returns -ENODEV if not.
+Otherwise the result of the notify() call is returned.
+
The advantage of using v4l2_subdev is that it is a generic struct and does
not contain any knowledge about the underlying hardware. So a driver might
contain several subdevs that use an I2C bus, but also a subdev that is