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Diffstat (limited to 'Documentation/video4linux/v4l2-framework.txt')
| -rw-r--r-- | Documentation/video4linux/v4l2-framework.txt | 10 |
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 |