Add documentation on using V4L2 file handles (v4l2_fh) in V4L2 drivers. Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxxxxxxxxxxxxx> --- Documentation/video4linux/v4l2-framework.txt | 37 ++++++++++++++++++++++++++ 1 files changed, 37 insertions(+), 0 deletions(-) diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt index 74d677c..bfaf0c5 100644 --- a/Documentation/video4linux/v4l2-framework.txt +++ b/Documentation/video4linux/v4l2-framework.txt @@ -695,3 +695,40 @@ The better way to understand it is to take a look at vivi driver. One of the main reasons for vivi is to be a videobuf usage example. the vivi_thread_tick() does the task that the IRQ callback would do on PCI drivers (or the irq callback on USB). + +struct v4l2_fh +-------------- + +struct v4l2_fh provides a way to easily keep file handle specific data +that is used by the V4L2 framework. + +struct v4l2_fh is allocated as a part of the driver's own file handle +structure and is set to file->private_data in the driver's open +function by the driver. Drivers can extract their own file handle +structure by using the container_of macro. + +Useful functions: + +- v4l2_fh_init() + + Initialise the file handle. This *MUST* be performed in the driver's + v4l2_file_operations->open() handler. + +- v4l2_fh_add() + + Add a v4l2_fh to video_device file handle list. May be called after + initialising the file handle. + +- v4l2_fh_del() + + Unassociate the file handle from video_device(). The file handle + exit function may now be called. + +- v4l2_fh_exit() + + Uninitialise the file handle. After uninitialisation the v4l2_fh + memory can be freed. + +The users of v4l2_fh know whether a driver uses v4l2_fh as its +file->private_data pointer by testing the V4L2_FL_USES_V4L2_FH bit in +video_device->flags. -- 1.5.6.5 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
