Reviewed-by: Hans Verkuil <hverkuil@xxxxxxxxx> On Monday 22 February 2010 16:51:33 Sakari Ailus wrote: > 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. > -- Hans Verkuil - video4linux developer - sponsored by TANDBERG -- 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
