diff options
Diffstat (limited to 'Documentation')
-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 df0247ed13d8..4207590b2ac8 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 | |||
94 | with ISA devices or when one device creates multiple PCI devices, thus making | 94 | with ISA devices or when one device creates multiple PCI devices, thus making |
95 | it impossible to associate v4l2_dev with a particular parent. | 95 | it impossible to associate v4l2_dev with a particular parent. |
96 | 96 | ||
97 | You can also supply a notify() callback that can be called by sub-devices to | ||
98 | notify you of events. Whether you need to set this depends on the sub-device. | ||
99 | Any notifications a sub-device supports must be defined in a header in | ||
100 | include/media/<subdevice>.h. | ||
101 | |||
97 | You unregister with: | 102 | You unregister with: |
98 | 103 | ||
99 | v4l2_device_unregister(struct v4l2_device *v4l2_dev); | 104 | 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 | |||
281 | v4l2_device_call_all(). That ensures that it will only go to the subdev | 286 | v4l2_device_call_all(). That ensures that it will only go to the subdev |
282 | that needs it. | 287 | that needs it. |
283 | 288 | ||
289 | If the sub-device needs to notify its v4l2_device parent of an event, then | ||
290 | it can call v4l2_subdev_notify(sd, notification, arg). This macro checks | ||
291 | whether there is a notify() callback defined and returns -ENODEV if not. | ||
292 | Otherwise the result of the notify() call is returned. | ||
293 | |||
284 | The advantage of using v4l2_subdev is that it is a generic struct and does | 294 | The advantage of using v4l2_subdev is that it is a generic struct and does |
285 | not contain any knowledge about the underlying hardware. So a driver might | 295 | not contain any knowledge about the underlying hardware. So a driver might |
286 | contain several subdevs that use an I2C bus, but also a subdev that is | 296 | contain several subdevs that use an I2C bus, but also a subdev that is |