接口设计
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ioctl 接口
用户态通过 /dev/videoX 节点的 ioctl() 接口与内核态 V4L2 框架、DVP 驱动进行交互。主要功能有：
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获取、设置格式
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申请、释放 Buf
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QBuf、DQBuf
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导出 dma-buf 文件描述符
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启动、停止 Stream
定义在include/uapi/linux/videodev2.h：
#define VIDIOC_QUERYCAP _IOR('V', 0, struct v4l2_capability) #define VIDIOC_ENUM_FMT _IOWR('V', 2, struct v4l2_fmtdesc) #define VIDIOC_G_FMT _IOWR('V', 4, struct v4l2_format) #define VIDIOC_S_FMT _IOWR('V', 5, struct v4l2_format) #define VIDIOC_REQBUFS _IOWR('V', 8, struct v4l2_requestbuffers) #define VIDIOC_QUERYBUF _IOWR('V', 9, struct v4l2_buffer) #define VIDIOC_G_FBUF _IOR('V', 10, struct v4l2_framebuffer) #define VIDIOC_S_FBUF _IOW('V', 11, struct v4l2_framebuffer) #define VIDIOC_OVERLAY _IOW('V', 14, int) #define VIDIOC_QBUF _IOWR('V', 15, struct v4l2_buffer) #define VIDIOC_EXPBUF _IOWR('V', 16, struct v4l2_exportbuffer) #define VIDIOC_DQBUF _IOWR('V', 17, struct v4l2_buffer) #define VIDIOC_STREAMON _IOW('V', 18, int) #define VIDIOC_STREAMOFF _IOW('V', 19, int) #define VIDIOC_G_PARM _IOWR('V', 21, struct v4l2_streamparm) #define VIDIOC_S_PARM _IOWR('V', 22, struct v4l2_streamparm) #define VIDIOC_G_STD _IOR('V', 23, v4l2_std_id) #define VIDIOC_S_STD _IOW('V', 24, v4l2_std_id) #define VIDIOC_ENUMSTD _IOWR('V', 25, struct v4l2_standard) #define VIDIOC_ENUMINPUT _IOWR('V', 26, struct v4l2_input) #define VIDIOC_G_CTRL _IOWR('V', 27, struct v4l2_control) #define VIDIOC_S_CTRL _IOWR('V', 28, struct v4l2_control) #define VIDIOC_QUERYCTRL _IOWR('V', 36, struct v4l2_queryctrl) #define VIDIOC_QUERYMENU _IOWR('V', 37, struct v4l2_querymenu) #define VIDIOC_G_INPUT _IOR('V', 38, int) #define VIDIOC_S_INPUT _IOWR('V', 39, int) #define VIDIOC_G_OUTPUT _IOR('V', 46, int) #define VIDIOC_S_OUTPUT _IOWR('V', 47, int) #define VIDIOC_ENUMOUTPUT _IOWR('V', 48, struct v4l2_output) #define VIDIOC_G_FREQUENCY _IOWR('V', 56, struct v4l2_frequency) #define VIDIOC_S_FREQUENCY _IOW('V', 57, struct v4l2_frequency) #define VIDIOC_CROPCAP _IOWR('V', 58, struct v4l2_cropcap) #define VIDIOC_G_CROP _IOWR('V', 59, struct v4l2_crop) #define VIDIOC_S_CROP _IOW('V', 60, struct v4l2_crop) #define VIDIOC_G_JPEGCOMP _IOR('V', 61, struct v4l2_jpegcompression) #define VIDIOC_S_JPEGCOMP _IOW('V', 62, struct v4l2_jpegcompression) #define VIDIOC_QUERYSTD _IOR('V', 63, v4l2_std_id) #define VIDIOC_TRY_FMT _IOWR('V', 64, struct v4l2_format) #define VIDIOC_G_PRIORITY _IOR('V', 67, __u32) /* enum v4l2_priority */ #define VIDIOC_S_PRIORITY _IOW('V', 68, __u32) /* enum v4l2_priority */ #define VIDIOC_G_SLICED_VBI_CAP _IOWR('V', 69, struct v4l2_sliced_vbi_cap) #define VIDIOC_LOG_STATUS _IO('V', 70) #define VIDIOC_G_EXT_CTRLS _IOWR('V', 71, struct v4l2_ext_controls) #define VIDIOC_S_EXT_CTRLS _IOWR('V', 72, struct v4l2_ext_controls) #define VIDIOC_TRY_EXT_CTRLS _IOWR('V', 73, struct v4l2_ext_controls) #define VIDIOC_ENUM_FRAMESIZES _IOWR('V', 74, struct v4l2_frmsizeenum) #define VIDIOC_ENUM_FRAMEINTERVALS _IOWR('V', 75, struct v4l2_frmivalenum) #define VIDIOC_G_ENC_INDEX _IOR('V', 76, struct v4l2_enc_idx) #define VIDIOC_ENCODER_CMD _IOWR('V', 77, struct v4l2_encoder_cmd) #define VIDIOC_TRY_ENCODER_CMD _IOWR('V', 78, struct v4l2_encoder_cmd)
V4l2 subdev 的外部接口
用户态通过/dev/v4l-subdevX 节点的 ioctl()接口与内核态 V4L2 框架、DVP 驱动、Sensor 驱动进行交互。主要功能有：
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获取、设置格式
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获取、设置帧间隔
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枚举支持的 MBUS 类型
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枚举支持的分辨率
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获取、设置区域裁剪
定义在
include/uapi/linux/v4l2-subdev.h：
#define VIDIOC_SUBDEV_G_FMT _IOWR('V', 4, struct v4l2_subdev_format) #define VIDIOC_SUBDEV_S_FMT _IOWR('V', 5, struct v4l2_subdev_format) #define VIDIOC_SUBDEV_G_FRAME_INTERVAL _IOWR('V', 21, struct v4l2_subdev_frame_interval) #define VIDIOC_SUBDEV_S_FRAME_INTERVAL _IOWR('V', 22, struct v4l2_subdev_frame_interval) #define VIDIOC_SUBDEV_ENUM_MBUS_CODE _IOWR('V', 2, struct v4l2_subdev_mbus_code_enum) #define VIDIOC_SUBDEV_ENUM_FRAME_SIZE _IOWR('V', 74, struct v4l2_subdev_frame_size_enum) #define VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL _IOWR('V', 75, struct v4l2_subdev_frame_interval_enum) #define VIDIOC_SUBDEV_G_CROP _IOWR('V', 59, struct v4l2_subdev_crop) #define VIDIOC_SUBDEV_S_CROP _IOWR('V', 60, struct v4l2_subdev_crop) #define VIDIOC_SUBDEV_G_SELECTION _IOWR('V', 61, struct v4l2_subdev_selection) #define VIDIOC_SUBDEV_S_SELECTION _IOWR('V', 62, struct v4l2_subdev_selection) /* The following ioctls are identical to the ioctls in videodev2.h */ #define VIDIOC_SUBDEV_G_STD _IOR('V', 23, v4l2_std_id) #define VIDIOC_SUBDEV_S_STD _IOW('V', 24, v4l2_std_id) #define VIDIOC_SUBDEV_ENUMSTD _IOWR('V', 25, struct v4l2_standard) #define VIDIOC_SUBDEV_G_EDID _IOWR('V', 40, struct v4l2_edid) #define VIDIOC_SUBDEV_S_EDID _IOWR('V', 41, struct v4l2_edid) #define VIDIOC_SUBDEV_QUERYSTD _IOR('V', 63, v4l2_std_id) #define VIDIOC_SUBDEV_S_DV_TIMINGS _IOWR('V', 87, struct v4l2_dv_timings) #define VIDIOC_SUBDEV_G_DV_TIMINGS _IOWR('V', 88, struct v4l2_dv_timings) #define VIDIOC_SUBDEV_ENUM_DV_TIMINGS _IOWR('V', 98, struct v4l2_enum_dv_timings) #define VIDIOC_SUBDEV_QUERY_DV_TIMINGS _IOR('V', 99, struct v4l2_dv_timings) #define VIDIOC_SUBDEV_DV_TIMINGS_CAP _IOWR('V', 100, struct v4l2_dv_timings_cap)