linux V4L2子系统——v4l2的结构体（3）之v4l2_subdev

备注：
  1. Kernel版本：5.4
  2. 使用工具：Source Insight 4.0

简介

子设备，负责实现具体的功能。可将其抽象为具体的某一摄像头传感器，如OV7740、OV7251、OV5640等。

每一个子设备驱动都必须有一个 v4l2_subdev 结构体，这个结构体可以作为独立的简单子设备存在，也可以嵌入到更大的结构体（自定义的子设备结构体）里面。通常会有一个由内核设置的低层次结构体（i2c_client，也就是上面说的 i2c 设备），它包含了一些设备数据，要调用 v4l2_set_subdevdata 来设置子设备私有数据指针指向它，这样的话就可以很方便的从 subdev 找到相关的 I2C 设备数据（这个要编程实现的时候才能够了解它的用意）。另外也需要设置低级别结构的私有数据指针指向 v4l2_subdev 结构体，方便从低级别的结构体访问 v4l2_subdev 结构体，达到双向访问的目的，对于 i2c_client 来说，可以用 i2c_set_clientdata 函数来设置，其它的需使用与之相应的函数来完成设置。

定义

struct v4l2_subdev

//源码：include/media/v4l2-subdev.h

/* Set this flag if this subdev is a i2c device. */
#define V4L2_SUBDEV_FL_IS_I2C			(1U << 0)	// 从设备是I2C设备
/* Set this flag if this subdev is a spi device. */
#define V4L2_SUBDEV_FL_IS_SPI			(1U << 1)	// 从设备是SPI设备
/* Set this flag if this subdev needs a device node. */
#define V4L2_SUBDEV_FL_HAS_DEVNODE		(1U << 2)	// 从设备需要设备节点
/*
 * Set this flag if this subdev generates events.
 * Note controls can send events, thus drivers exposing controls
 * should set this flag.
 */
#define V4L2_SUBDEV_FL_HAS_EVENTS		(1U << 3)	// 从设备会产生事件

/**
 * struct v4l2_subdev - describes a V4L2 sub-device
 *
 * @entity: pointer to &struct media_entity
 * @list: List of sub-devices
 * @owner: The owner is the same as the driver's &struct device owner.
 * @owner_v4l2_dev: true if the &sd->owner matches the owner of @v4l2_dev->dev
 *	owner. Initialized by v4l2_device_register_subdev().
 * @flags: subdev flags. Can be:
 *   %V4L2_SUBDEV_FL_IS_I2C - Set this flag if this subdev is a i2c device;
 *   %V4L2_SUBDEV_FL_IS_SPI - Set this flag if this subdev is a spi device;
 *   %V4L2_SUBDEV_FL_HAS_DEVNODE - Set this flag if this subdev needs a
 *   device node;
 *   %V4L2_SUBDEV_FL_HAS_EVENTS -  Set this flag if this subdev generates
 *   events.
 *
 * @v4l2_dev: pointer to struct &v4l2_device
 * @ops: pointer to struct &v4l2_subdev_ops
 * @internal_ops: pointer to struct &v4l2_subdev_internal_ops.
 *	Never call these internal ops from within a driver!
 * @ctrl_handler: The control handler of this subdev. May be NULL.
 * @name: Name of the sub-device. Please notice that the name must be unique.
 * @grp_id: can be used to group similar subdevs. Value is driver-specific
 * @dev_priv: pointer to private data
 * @host_priv: pointer to private data used by the device where the subdev
 *	is attached.
 * @devnode: subdev device node
 * @dev: pointer to the physical device, if any
 * @fwnode: The fwnode_handle of the subdev, usually the same as
 *	    either dev->of_node->fwnode or dev->fwnode (whichever is non-NULL).
 * @async_list: Links this subdev to a global subdev_list or @notifier->done
 *	list.
 * @asd: Pointer to respective &struct v4l2_async_subdev.
 * @notifier: Pointer to the managing notifier.
 * @subdev_notifier: A sub-device notifier implicitly registered for the sub-
 *		     device using v4l2_device_register_sensor_subdev().
 * @pdata: common part of subdevice platform data
 *
 * Each instance of a subdev driver should create this struct, either
 * stand-alone or embedded in a larger struct.
 *
 * This structure should be initialized by v4l2_subdev_init() or one of
 * its variants: v4l2_spi_subdev_init(), v4l2_i2c_subdev_init().
 */
struct v4l2_subdev {
#if defined(CONFIG_MEDIA_CONTROLLER)
	struct media_entity entity;
#endif
	struct list_head list;	// 子设备串联链表
	struct module *owner;	// 属于那个模块，一般指向i2c_lient驱动模块
	bool owner_v4l2_dev;
	u32 flags;				// 标志位，确定该设备属于那种设备，由V4L2_SUBDEV_FL_IS_XX宏确定

	// 指向父设备
	struct v4l2_device *v4l2_dev;

	 // v4l2子设备的操作函数集合
	const struct v4l2_subdev_ops *ops;

	// 提供给v4l2框架的操作函数，只有v4l2框架会调用，驱动不使用
	const struct v4l2_subdev_internal_ops *internal_ops;

	// subdev控制接口
	struct v4l2_ctrl_handler *ctrl_handler;

	// name must be unique
	// 从设备的名称，必须独一无二
	char name[V4L2_SUBDEV_NAME_SIZE];

	// 从设备组的ID，由驱动定义，相似的从设备可以编为一组
	u32 grp_id;

	// 从设备私有数据指针，一般指向i2c_client的设备结构体dev
	void *dev_priv;

	// 主设备私有数据指针，一般指向v4l2_device嵌入的结构体
	void *host_priv;

	// 指向video设备结构体
	struct video_device *devnode;

	// 指向物理设备
	struct device *dev;
	struct fwnode_handle *fwnode;

	// 将所有从设备连接到全局subdev_list链表或notifier->done链表
	struct list_head async_list;

	// 指向struct v4l2_async_subdev，用于异步事件
	struct v4l2_async_subdev *asd;

	// 指向管理的notifier，用于主设备和从设备的异步关联
	struct v4l2_async_notifier *notifier;
	struct v4l2_async_notifier *subdev_notifier;

	/* common part of subdevice platform data */
	struct v4l2_subdev_platform_data *pdata;
};

struct v4l2_subdev_ops

//源码：include/media/v4l2-subdev.h
/**
 * struct v4l2_subdev_ops - Subdev operations
 *
 * @core: pointer to &struct v4l2_subdev_core_ops. Can be %NULL
 * @tuner: pointer to &struct v4l2_subdev_tuner_ops. Can be %NULL
 * @audio: pointer to &struct v4l2_subdev_audio_ops. Can be %NULL
 * @video: pointer to &struct v4l2_subdev_video_ops. Can be %NULL
 * @vbi: pointer to &struct v4l2_subdev_vbi_ops. Can be %NULL
 * @ir: pointer to &struct v4l2_subdev_ir_ops. Can be %NULL
 * @sensor: pointer to &struct v4l2_subdev_sensor_ops. Can be %NULL
 * @pad: pointer to &struct v4l2_subdev_pad_ops. Can be %NULL
 */
struct v4l2_subdev_ops {
	//视频设备通用的操作：初始化、加载FW、上电和RESET等
	const struct v4l2_subdev_core_ops	*core;

	/* 调谐器操作合集 */
	const struct v4l2_subdev_tuner_ops	*tuner;

	/* 音频操作合集 */
	const struct v4l2_subdev_audio_ops	*audio;

	//视频设备的特有操作：设置帧率、裁剪图像、开关视频流等
	const struct v4l2_subdev_video_ops	*video; /* 视频操作合集 */
	const struct v4l2_subdev_vbi_ops	*vbi;
	const struct v4l2_subdev_ir_ops		*ir;
	const struct v4l2_subdev_sensor_ops	*sensor;
	const struct v4l2_subdev_pad_ops	*pad;
};

struct v4l2_subdev_core_ops

//源码：include/media/v4l2-subdev.h
/**
 * struct v4l2_subdev_core_ops - Define core ops callbacks for subdevs
 *
 * @log_status: callback for VIDIOC_LOG_STATUS() ioctl handler code.
 *
 * @s_io_pin_config: configure one or more chip I/O pins for chips that
 *	multiplex different internal signal pads out to IO pins.  This function
 *	takes a pointer to an array of 'n' pin configuration entries, one for
 *	each pin being configured.  This function could be called at times
 *	other than just subdevice initialization.
 *
 * @init: initialize the sensor registers to some sort of reasonable default
 *	values. Do not use for new drivers and should be removed in existing
 *	drivers.
 *
 * @load_fw: load firmware.
 *
 * @reset: generic reset command. The argument selects which subsystems to
 *	reset. Passing 0 will always reset the whole chip. Do not use for new
 *	drivers without discussing this first on the linux-media mailinglist.
 *	There should be no reason normally to reset a device.
 *
 * @s_gpio: set GPIO pins. Very simple right now, might need to be extended with
 *	a direction argument if needed.
 *
 * @ioctl: called at the end of ioctl() syscall handler at the V4L2 core.
 *	   used to provide support for private ioctls used on the driver.
 *
 * @compat_ioctl32: called when a 32 bits application uses a 64 bits Kernel,
 *		    in order to fix data passed from/to userspace.
 *
 * @g_register: callback for VIDIOC_DBG_G_REGISTER() ioctl handler code.
 *
 * @s_register: callback for VIDIOC_DBG_S_REGISTER() ioctl handler code.
 *
 * @s_power: puts subdevice in power saving mode (on == 0) or normal operation
 *	mode (on == 1).
 *
 * @interrupt_service_routine: Called by the bridge chip's interrupt service
 *	handler, when an interrupt status has be raised due to this subdev,
 *	so that this subdev can handle the details.  It may schedule work to be
 *	performed later.  It must not sleep. **Called from an IRQ context**.
 *
 * @subscribe_event: used by the drivers to request the control framework that
 *		     for it to be warned when the value of a control changes.
 *
 * @unsubscribe_event: remove event subscription from the control framework.
 */
struct v4l2_subdev_core_ops {
	int (*log_status)(struct v4l2_subdev *sd);	/* 状态消息 */
	
	int (*s_io_pin_config)(struct v4l2_subdev *sd, size_t n,
				      struct v4l2_subdev_io_pin_config *pincfg);
	
	int (*init)(struct v4l2_subdev *sd, u32 val);	/* 初始化设备 */
	
	int (*load_fw)(struct v4l2_subdev *sd);			/* 加载firmware */
	int (*reset)(struct v4l2_subdev *sd, u32 val);	/* 重置设备 */
	int (*s_gpio)(struct v4l2_subdev *sd, u32 val);	/* 设置gpio */
	long (*ioctl)(struct v4l2_subdev *sd, unsigned int cmd, void *arg); /* 处理特殊命令 */
#ifdef CONFIG_COMPAT
	long (*compat_ioctl32)(struct v4l2_subdev *sd, unsigned int cmd,
			       unsigned long arg);
#endif
#ifdef CONFIG_VIDEO_ADV_DEBUG
	int (*g_register)(struct v4l2_subdev *sd, struct v4l2_dbg_register *reg); /* 获取寄存器值 */
	int (*s_register)(struct v4l2_subdev *sd, const struct v4l2_dbg_register *reg); /* 设置寄存器值 */
#endif
	int (*s_power)(struct v4l2_subdev *sd, int on); /* 控制设备上下电 */

	int (*interrupt_service_routine)(struct v4l2_subdev *sd,
						u32 status, bool *handled); /* 中断服务函数 */
	
	int (*subscribe_event)(struct v4l2_subdev *sd, struct v4l2_fh *fh,
			       struct v4l2_event_subscription *sub);
	int (*unsubscribe_event)(struct v4l2_subdev *sd, struct v4l2_fh *fh,
				 struct v4l2_event_subscription *sub);
};

struct v4l2_subdev_tuner_ops

//源码：include/media/v4l2-subdev.h
/**
 * struct v4l2_subdev_tuner_ops - Callbacks used when v4l device was opened
 *	in radio mode.
 *
 * @standby: puts the tuner in standby mode. It will be woken up
 *	     automatically the next time it is used.
 *
 * @s_radio: callback that switches the tuner to radio mode.
 *	     drivers should explicitly call it when a tuner ops should
 *	     operate on radio mode, before being able to handle it.
 *	     Used on devices that have both AM/FM radio receiver and TV.
 *
 * @s_frequency: callback for VIDIOC_S_FREQUENCY() ioctl handler code.
 *
 * @g_frequency: callback for VIDIOC_G_FREQUENCY() ioctl handler code.
 *		 freq->type must be filled in. Normally done by video_ioctl2()
 *		 or the bridge driver.
 *
 * @enum_freq_bands: callback for VIDIOC_ENUM_FREQ_BANDS() ioctl handler code.
 *
 * @g_tuner: callback for VIDIOC_G_TUNER() ioctl handler code.
 *
 * @s_tuner: callback for VIDIOC_S_TUNER() ioctl handler code. @vt->type must be
 *	     filled in. Normally done by video_ioctl2 or the
 *	     bridge driver.
 *
 * @g_modulator: callback for VIDIOC_G_MODULATOR() ioctl handler code.
 *
 * @s_modulator: callback for VIDIOC_S_MODULATOR() ioctl handler code.
 *
 * @s_type_addr: sets tuner type and its I2C addr.
 *
 * @s_config: sets tda9887 specific stuff, like port1, port2 and qss
 *
 * .. note::
 *
 *	On devices that have both AM/FM and TV, it is up to the driver
 *	to explicitly call s_radio when the tuner should be switched to
 *	radio mode, before handling other &struct v4l2_subdev_tuner_ops
 *	that would require it. An example of such usage is::
 *
 *	  static void s_frequency(void *priv, const struct v4l2_frequency *f)
 *	  {
 *		...
 *		if (f.type == V4L2_TUNER_RADIO)
 *			v4l2_device_call_all(v4l2_dev, 0, tuner, s_radio);
 *		...
 *		v4l2_device_call_all(v4l2_dev, 0, tuner, s_frequency);
 *	  }
 */
struct v4l2_subdev_tuner_ops {
	int (*standby)(struct v4l2_subdev *sd); /* 控制standby模式 */
	int (*s_radio)(struct v4l2_subdev *sd); /* 设置无线设备信息 */
	int (*s_frequency)(struct v4l2_subdev *sd, const struct v4l2_frequency *freq); /* 设置频率 */
	int (*g_frequency)(struct v4l2_subdev *sd, struct v4l2_frequency *freq);/* 获取频率 */
	int (*enum_freq_bands)(struct v4l2_subdev *sd, struct v4l2_frequency_band *band);
	
	int (*g_tuner)(struct v4l2_subdev *sd, struct v4l2_tuner *vt);		/* 获取调谐器信息 */
	int (*s_tuner)(struct v4l2_subdev *sd, const struct v4l2_tuner *vt);/* 设置调谐器信息 */

	int (*g_modulator)(struct v4l2_subdev *sd, struct v4l2_modulator *vm); /* 获取调幅器信息 */
	int (*s_modulator)(struct v4l2_subdev *sd, const struct v4l2_modulator *vm); /* 设置调幅器信息 */
	int (*s_type_addr)(struct v4l2_subdev *sd, struct tuner_setup *type); /* 安装调谐器 */
	int (*s_config)(struct v4l2_subdev *sd, const struct v4l2_priv_tun_config *config); /* 设置配置信息 */
};

struct v4l2_subdev_audio_ops

//源码：include/media/v4l2-subdev.h
/**
 * struct v4l2_subdev_audio_ops - Callbacks used for audio-related settings
 *
 * @s_clock_freq: set the frequency (in Hz) of the audio clock output.
 *	Used to slave an audio processor to the video decoder, ensuring that
 *	audio and video remain synchronized. Usual values for the frequency
 *	are 48000, 44100 or 32000 Hz. If the frequency is not supported, then
 *	-EINVAL is returned.
 *
 * @s_i2s_clock_freq: sets I2S speed in bps. This is used to provide a standard
 *	way to select I2S clock used by driving digital audio streams at some
 *	board designs. Usual values for the frequency are 1024000 and 2048000.
 *	If the frequency is not supported, then %-EINVAL is returned.
 *
 * @s_routing: used to define the input and/or output pins of an audio chip,
 *	and any additional configuration data.
 *	Never attempt to use user-level input IDs (e.g. Composite, S-Video,
 *	Tuner) at this level. An i2c device shouldn't know about whether an
 *	input pin is connected to a Composite connector, become on another
 *	board or platform it might be connected to something else entirely.
 *	The calling driver is responsible for mapping a user-level input to
 *	the right pins on the i2c device.
 *
 * @s_stream: used to notify the audio code that stream will start or has
 *	stopped.
 */
struct v4l2_subdev_audio_ops {
	int (*s_clock_freq)(struct v4l2_subdev *sd, u32 freq);		/* 设置音频设备频率 */
	int (*s_i2s_clock_freq)(struct v4l2_subdev *sd, u32 freq);	/* 设置i2s总线频率 */
	int (*s_routing)(struct v4l2_subdev *sd, u32 input, u32 output, u32 config); /* 设置音频路由 */
	int (*s_stream)(struct v4l2_subdev *sd, int enable); /* 控制音频流 */
};

struct v4l2_subdev_video_ops

//源码：include/media/v4l2-subdev.h


/**
 * struct v4l2_subdev_video_ops - Callbacks used when v4l device was opened
 *				  in video mode.
 *
 * @s_routing: see s_routing in audio_ops, except this version is for video
 *	devices.
 *
 * @s_crystal_freq: sets the frequency of the crystal used to generate the
 *	clocks in Hz. An extra flags field allows device specific configuration
 *	regarding clock frequency dividers, etc. If not used, then set flags
 *	to 0. If the frequency is not supported, then -EINVAL is returned.
 *
 * @g_std: callback for VIDIOC_G_STD() ioctl handler code.
 *
 * @s_std: callback for VIDIOC_S_STD() ioctl handler code.
 *
 * @s_std_output: set v4l2_std_id for video OUTPUT devices. This is ignored by
 *	video input devices.
 *
 * @g_std_output: get current standard for video OUTPUT devices. This is ignored
 *	by video input devices.
 *
 * @querystd: callback for VIDIOC_QUERYSTD() ioctl handler code.
 *
 * @g_tvnorms: get &v4l2_std_id with all standards supported by the video
 *	CAPTURE device. This is ignored by video output devices.
 *
 * @g_tvnorms_output: get v4l2_std_id with all standards supported by the video
 *	OUTPUT device. This is ignored by video capture devices.
 *
 * @g_input_status: get input status. Same as the status field in the
 *	&struct &v4l2_input
 *
 * @s_stream: used to notify the driver that a video stream will start or has
 *	stopped.
 *
 * @g_pixelaspect: callback to return the pixelaspect ratio.
 *
 * @g_frame_interval: callback for VIDIOC_SUBDEV_G_FRAME_INTERVAL()
 *		      ioctl handler code.
 *
 * @s_frame_interval: callback for VIDIOC_SUBDEV_S_FRAME_INTERVAL()
 *		      ioctl handler code.
 *
 * @s_dv_timings: Set custom dv timings in the sub device. This is used
 *	when sub device is capable of setting detailed timing information
 *	in the hardware to generate/detect the video signal.
 *
 * @g_dv_timings: Get custom dv timings in the sub device.
 *
 * @query_dv_timings: callback for VIDIOC_QUERY_DV_TIMINGS() ioctl handler code.
 *
 * @g_mbus_config: get supported mediabus configurations
 *
 * @s_mbus_config: set a certain mediabus configuration. This operation is added
 *	for compatibility with soc-camera drivers and should not be used by new
 *	software.
 *
 * @s_rx_buffer: set a host allocated memory buffer for the subdev. The subdev
 *	can adjust @size to a lower value and must not write more data to the
 *	buffer starting at @data than the original value of @size.
 */
struct v4l2_subdev_video_ops {
	int (*s_routing)(struct v4l2_subdev *sd, u32 input, u32 output, u32 config); /* 设置视频路由 */
	int (*s_crystal_freq)(struct v4l2_subdev *sd, u32 freq, u32 flags);			 /* 设置设备频率 */
	int (*g_std)(struct v4l2_subdev *sd, v4l2_std_id *norm);
	int (*s_std)(struct v4l2_subdev *sd, v4l2_std_id norm);
	int (*s_std_output)(struct v4l2_subdev *sd, v4l2_std_id std);				 /* 设置标准输出 */
	int (*g_std_output)(struct v4l2_subdev *sd, v4l2_std_id *std);				 /* 获取标准输出 */
	int (*querystd)(struct v4l2_subdev *sd, v4l2_std_id *std);					 /* 查询标准 */
	int (*g_tvnorms)(struct v4l2_subdev *sd, v4l2_std_id *std);
	int (*g_tvnorms_output)(struct v4l2_subdev *sd, v4l2_std_id *std);
	int (*g_input_status)(struct v4l2_subdev *sd, u32 *status);					 /* 获取输入状态 */
	int (*s_stream)(struct v4l2_subdev *sd, int enable);						 /* 设置数据流 */
	int (*g_pixelaspect)(struct v4l2_subdev *sd, struct v4l2_fract *aspect);

	// 获取帧间隔参数（帧率）
	int (*g_frame_interval)(struct v4l2_subdev *sd,
				struct v4l2_subdev_frame_interval *interval);
	int (*s_frame_interval)(struct v4l2_subdev *sd,
				struct v4l2_subdev_frame_interval *interval);


	int (*s_dv_timings)(struct v4l2_subdev *sd,
			struct v4l2_dv_timings *timings);
	int (*g_dv_timings)(struct v4l2_subdev *sd,
			struct v4l2_dv_timings *timings);
	int (*query_dv_timings)(struct v4l2_subdev *sd,
			struct v4l2_dv_timings *timings);

	// 获取总线配置，对于 MIPI接口，
	// sensor驱动内若支持不同 lane数配置或者支持 HDR,
	// 通过这个接口返回当前 sensor 工作模式下的MIPI配置
	int (*g_mbus_config)(struct v4l2_subdev *sd,
			     struct v4l2_mbus_config *cfg);
	int (*s_mbus_config)(struct v4l2_subdev *sd,
			     const struct v4l2_mbus_config *cfg);
	int (*s_rx_buffer)(struct v4l2_subdev *sd, void *buf,
			   unsigned int *size);
};

struct v4l2_subdev_pad_ops

//源码：include/media/v4l2-subdev.h
/**
 * struct v4l2_subdev_pad_ops - v4l2-subdev pad level operations
 *
 * @init_cfg: initialize the pad config to default values
 * @enum_mbus_code: callback for VIDIOC_SUBDEV_ENUM_MBUS_CODE() ioctl handler
 *		    code.
 * @enum_frame_size: callback for VIDIOC_SUBDEV_ENUM_FRAME_SIZE() ioctl handler
 *		     code.
 *
 * @enum_frame_interval: callback for VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL() ioctl
 *			 handler code.
 *
 * @get_fmt: callback for VIDIOC_SUBDEV_G_FMT() ioctl handler code.
 *
 * @set_fmt: callback for VIDIOC_SUBDEV_S_FMT() ioctl handler code.
 *
 * @get_selection: callback for VIDIOC_SUBDEV_G_SELECTION() ioctl handler code.
 *
 * @set_selection: callback for VIDIOC_SUBDEV_S_SELECTION() ioctl handler code.
 *
 * @get_edid: callback for VIDIOC_SUBDEV_G_EDID() ioctl handler code.
 *
 * @set_edid: callback for VIDIOC_SUBDEV_S_EDID() ioctl handler code.
 *
 * @dv_timings_cap: callback for VIDIOC_SUBDEV_DV_TIMINGS_CAP() ioctl handler
 *		    code.
 *
 * @enum_dv_timings: callback for VIDIOC_SUBDEV_ENUM_DV_TIMINGS() ioctl handler
 *		     code.
 *
 * @link_validate: used by the media controller code to check if the links
 *		   that belongs to a pipeline can be used for stream.
 *
 * @get_frame_desc: get the current low level media bus frame parameters.
 *
 * @set_frame_desc: set the low level media bus frame parameters, @fd array
 *                  may be adjusted by the subdev driver to device capabilities.
 */
struct v4l2_subdev_pad_ops {
	int (*init_cfg)(struct v4l2_subdev *sd,
			struct v4l2_subdev_pad_config *cfg);
	
    // 枚举当前CIS 驱动支持数据格式
    int (*enum_mbus_code)(struct v4l2_subdev *sd,
			      struct v4l2_subdev_pad_config *cfg,
			      struct v4l2_subdev_mbus_code_enum *code);
                        
    // 枚举当前CIS 驱动支持分辨率    
    int (*enum_frame_size)(struct v4l2_subdev *sd,
			       struct v4l2_subdev_pad_config *cfg,
			       struct v4l2_subdev_frame_size_enum *fse);
	
    // 枚举sensor支持的帧间隔，包含分辨率
    int (*enum_frame_interval)(struct v4l2_subdev *sd,
				   struct v4l2_subdev_pad_config *cfg,
				   struct v4l2_subdev_frame_interval_enum *fie);
	
    // 枚举当前CIS 驱动支持分辨率    
    int (*get_fmt)(struct v4l2_subdev *sd,
		       struct v4l2_subdev_pad_config *cfg,
		       struct v4l2_subdev_format *format);
	
    //设置CIS 驱动输出数据格式以及分辨率，务必实现
    int (*set_fmt)(struct v4l2_subdev *sd,
		       struct v4l2_subdev_pad_config *cfg,
		       struct v4l2_subdev_format *format);
	
    // 配置裁剪参数，isp输入的宽度要求16对齐，高度 8 对齐
    int (*get_selection)(struct v4l2_subdev *sd,
			     struct v4l2_subdev_pad_config *cfg,
			     struct v4l2_subdev_selection *sel);
	int (*set_selection)(struct v4l2_subdev *sd,
			     struct v4l2_subdev_pad_config *cfg,
			     struct v4l2_subdev_selection *sel);
	int (*get_edid)(struct v4l2_subdev *sd, struct v4l2_edid *edid);
	int (*set_edid)(struct v4l2_subdev *sd, struct v4l2_edid *edid);
	int (*dv_timings_cap)(struct v4l2_subdev *sd,
			      struct v4l2_dv_timings_cap *cap);
	int (*enum_dv_timings)(struct v4l2_subdev *sd,
			       struct v4l2_enum_dv_timings *timings);
#ifdef CONFIG_MEDIA_CONTROLLER
	int (*link_validate)(struct v4l2_subdev *sd, struct media_link *link,
			     struct v4l2_subdev_format *source_fmt,
			     struct v4l2_subdev_format *sink_fmt);
#endif /* CONFIG_MEDIA_CONTROLLER */
	int (*get_frame_desc)(struct v4l2_subdev *sd, unsigned int pad,
			      struct v4l2_mbus_frame_desc *fd);
	int (*set_frame_desc)(struct v4l2_subdev *sd, unsigned int pad,
			      struct v4l2_mbus_frame_desc *fd);
};