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NetBSD 6.1.5 - man page for video (netbsd section 9)

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VIDEO(9)			  BSD Kernel Developer's Manual 			 VIDEO(9)

NAME
     video -- interface between low and high level video drivers

SYNOPSIS
     #include <dev/video_if.h>

     device_t
     video_attach_mi(const struct video_hw_if *hw_if, device_t hw_dev);

     void
     video_submit_payload(device_t vl_dev, const struct video_payload *payload);

DESCRIPTION
     The video device driver is divided into a high level, machine independent layer, and a low
     level hardware dependent layer.  The interface between these is the video_hw_if structure
     function pointers called by the video layer, and video layer functions called by the hard-
     ware driver.

     The high level video driver attaches to the low level driver when the latter calls
     video_attach_mi.  The video_hw_if struct is as shown below.  dev is the device struct for
     the hardware device.  Return value is the video layer device.

     struct video_hw_if {
	     int     (*open)(void *, int); /* open hardware */
	     void    (*close)(void *);	   /* close hardware */

	     const char *    (*get_devname)(void *);

	     int     (*enum_format)(void *, uint32_t, struct video_format *);
	     int     (*get_format)(void *, struct video_format *);
	     int     (*set_format)(void *, struct video_format *);
	     int     (*try_format)(void *, struct video_format *);

	     int     (*start_transfer)(void *);
	     int     (*stop_transfer)(void *);

	     int     (*control_iter_init)(void *, struct video_control_iter *);
	     int     (*control_iter_next)(void *, struct video_control_iter *);
	     int     (*get_control_desc_group)(void *,
					       struct video_control_desc_group *);
	     int     (*get_control_group)(void *, struct video_control_group *);
	     int     (*set_control_group)(void *, const struct video_control_group *);
     };

     The upper layer of the video driver allocates buffers for video samples.  The hardware
     driver submits data to the video layer with video_submit_payload.	vl_dev is the video layer
     device returned by video_attach_mi.

     struct video_payload {
	     const uint8_t   *data;
	     size_t	     size;
	     int	     frameno;
	     bool	     end_of_frame;
     };

     data    Pointer to the video data for this payload.  This may only be a portion of the data
	     in one video sample or frame.

     size    Size in bytes of the video data in this payload

     frameno
	     Frame number to which this payload belongs.  The hardware driver must toggle the
	     frame number between 0 and 1 so the video layer can detect sample or frame bound-
	     aries.

     end_of_frame
	     Optional end of frame marker.  If the hardware layer sets this, the video layer can
	     immediately pass the completed sample or frame to userspace rather than waiting for
	     the next payload to toggle frameno.

HARDWARE-LAYER FUNCTIONS
     The fields of video_hw_if are described in some more detail below.  Some fields are optional
     and can be set to NULL if not needed.

     int open(void *hdl, int flags)
	     optional, is called when the video device is opened.  It should initialize the hard-
	     ware for I/O.  Every successful call to open is matched by a call to close.  Return
	     0 on success, otherwise an error code.

     void close(void *hdl)
	     optional, is called when the audio device is closed.

     const char * get_devname(void *hdl)
	     mandatory, returns a NUL-terminated string naming the device, e.g. a vendor and
	     product model name.

     int enum_format(void *hdl, uint32_t index, struct video_format *format);
	     mandatory, called with an index from 0 to max_index - 1.  Fills format with the for-
	     mat description at that index.  Returns 0 on success, otherwise an error code.

     int get_format(void *hdl, struct video_format *format)
	     mandatory, fills format with the current video format.  There should be a default
	     format so this function works before and streaming has begun.  Returns 0 on success,
	     otherwise an error code.

     int set_format(void *hdl, struct video_format *format)
	     mandatory, sets the format of the video stream based on format.  Fills format with
	     the actual format used which may not be the same as requested.  Returns 0 on suc-
	     cess, otherwise an error code.

     int try_format(void *hdl, struct video_format *format)
	     optional, like set_format but does not actually change the stream format, just
	     checks what is available.	Returns 0 on success, otherwise an error code.

     int start_transfer(void *hdl)
	     mandatory, starts the capture of video frames.  Incoming video data must be submit-
	     ted to the video layer with repeated calls to video_submit_payload().

     int stop_transfer(void *hdl)

     int control_iter_init(void *hdl, struct video_control_iter *)
	     Does nothing at this time.

     int control_iter_next(void *hdl, struct video_control_iter *)
	     Does nothing at this time.

     int get_control_group(void *hdl, struct video_control_group *)

     int set_control_group(void *hdl, struct video_control_group *)

SEE ALSO
     video(4)

AUTHORS
     Patrick Mahoney <pat@polycrystal.org>

BUGS
     Incomplete.  Only supports a single video capture stream.	Does not support output streams.
     Format handling may change in the future.	Control handling may change.  Current design
     requires copying all incoming video data.

BSD					  July 24, 2008 				      BSD
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