3.2 函式繫結

其中v4l2_file_operations和v4l2_ioctl_ops是必須實現的。而v4l2_subdev_ops下的八類ops中，v4l2_subdev_core_ops是必須實現的，其餘需要根據裝置型別選擇實現的。比如video capture類裝置需要實現v4l2_subdev_core_ops, v4l2_subdev_video_ops。

• v4l2_file_operations：實現檔案類操作，比如open,close,read,write,mmap等。但是ioctl是不需要實現的，一般都是用video_ioctl2代替。例如linux/drivers/media/video/soc_camera.c檔案中soc_camera_fops的實現：

static struct v4l2_file_operations soc_camera_fops = {
    .owner          = THIS_MODULE,
    .open           = soc_camera_open,
    .release        = soc_camera_close,
    .unlocked_ioctl = video_ioctl2,
    .read           = soc_camera_read,
    .mmap           = soc_camera_mmap,
    .poll           =
 
 soc_camera_poll,
};

• v4l2_ioctl_ops：V4L2匯出給應用層使用的所有ioctl都是在這個地方實現的。但不必全部實現，只實現自己相關的ioctl即可。例如linux/drivers/media/video/soc_camera.c中soc_camera_ioctl_ops的實現：

static const struct v4l2_ioctl_ops soc_camera_ioctl_ops = {
    .vidioc_querycap         = soc_camera_querycap,
    .vidioc_try_fmt_vid_cap  = soc_camera_try_fmt_vid_cap
 
,
    .vidioc_g_fmt_vid_cap    = soc_camera_g_fmt_vid_cap,
    .vidioc_s_fmt_vid_cap    = soc_camera_s_fmt_vid_cap,
    .vidioc_enum_fmt_vid_cap = soc_camera_enum_fmt_vid_cap,
    .vidioc_enum_input       = soc_camera_enum_input,
    .vidioc_g_input          = soc_camera_g_input,
    .vidioc_s_input          = soc_camera_s_input,
    .vidioc_s_std            = soc_camera_s_std,
    .vidioc_g_std            = soc_camera_g_std,
    .vidioc_enum_framesizes  = soc_camera_enum_fsizes,
    .vidioc_reqbufs          = soc_camera_reqbufs,
    .vidioc_querybuf         = soc_camera_querybuf,
    .vidioc_qbuf             = soc_camera_qbuf,
    .vidioc_dqbuf            = soc_camera_dqbuf,
    .vidioc_create_bufs      = soc_camera_create_bufs,
    .vidioc_prepare_buf      = soc_camera_prepare_buf,
    .vidioc_streamon         = soc_camera_streamon,
    .vidioc_streamoff        = soc_camera_streamoff,
    .vidioc_cropcap          = soc_camera_cropcap,
    .vidioc_g_crop           = soc_camera_g_crop,
    .vidioc_s_crop           = soc_camera_s_crop,
    .vidioc_g_parm           = soc_camera_g_parm,
    .vidioc_s_parm           = soc_camera_s_parm,
    .vidioc_g_chip_ident     = soc_camera_g_chip_ident,
#ifdef CONFIG_VIDEO_ADV_DEBUG
    .vidioc_g_register       = soc_camera_g_register,
    .vidioc_s_register       = soc_camera_s_register,
#endif
};

• v4l2_subdev_ops：v4l2_subdev有可能需要實現的ops的總合。分為8類，core,audio,video,vbi,tuner......等。例如，

  linuxdriversmediavideosoc_camera_platform.c中platform_subdev_ops的實現

static struct v4l2_subdev_video_ops platform_subdev_video_ops = {
    .s_stream       = soc_camera_platform_s_stream,
    .enum_mbus_fmt  = soc_camera_platform_enum_fmt,
    .cropcap        = soc_camera_platform_cropcap,
    .g_crop         = soc_camera_platform_g_crop,
    .try_mbus_fmt   = soc_camera_platform_fill_fmt,
    .g_mbus_fmt     = soc_camera_platform_fill_fmt,
    .s_mbus_fmt     = soc_camera_platform_fill_fmt,
    .g_mbus_config  = soc_camera_platform_g_mbus_config,
};

static struct v4l2_subdev_ops platform_subdev_ops = {
    .core   = &platform_subdev_core_ops,
    .video  = &platform_subdev_video_ops,
};

函式繫結只是將驅動所實現的函式賦值給相關的變數即可。