29 Linux MIPI摄像头驱动

在 Linux 中开发 MIPI 摄像头驱动，涉及到多方面的工作，包括设备树（DTS）配置、V4L2 子设备的注册、以及实现必要的 V4L2 接口。

这里我们来讨论一款MIPI接口的摄像头OV13855, OV13855 是一款 CMOS 图像传感器，使用 MIPI CSI-2 接口将数据传输给主机。因此，驱动开发主要围绕配置 MIPI 接口、传感器初始化以及与 V4L2 框架的集成。

29.1 DTS配置

设备树文件描述了硬件的连接和配置。OV13855 是一个 I2C 设备，因此我们需要在 DTS 中描述 I2C 接口和 MIPI CSI 接口。以下是设备树配置的关键部分：

/ {
    vcc_mipidphy0: vcc-mipidphy0-regulator {
        compatible = "regulator-fixed";
        gpio = <&gpio1 RK_PB2 GPIO_ACTIVE_HIGH>;
        pinctrl-names = "default";
        pinctrl-0 = <&mipidphy0_pwr>;
        regulator-name = "vcc_mipidphy0";
        enable-active-high;
        //regulator-always-on;
        //regulator-boot-on;
    };
};
/******    common   ******/
&rkcif {
    status = "okay";
};

&rkcif_mmu {
    status = "okay";
};

&i2c3 {
    status = "okay";

    ov13855_dph0: ov13855-dph0@10 {
        compatible = "ovti,ov13855";
        status = "okay";
        reg = <0x10>;
        clocks = <&cru CLK_MIPI_CAMARAOUT_M1>;
        clock-names = "xvclk";
        power-domains = <&power RK3588_PD_VI>;
        pinctrl-names = "default";
        pinctrl-0 = <&mipim0_camera1_clk >; //1b6
        rockchip,grf = <&sys_grf>;
        reset-gpios = <&gpio1 RK_PA3 GPIO_ACTIVE_HIGH>;
        pwdn-gpios = <&gpio1 RK_PA2 GPIO_ACTIVE_HIGH>;
        avdd-supply = <&vcc_mipidphy0>;
        rockchip,camera-module-index = <1>;
        rockchip,camera-module-facing = "front";
        rockchip,camera-module-name = "CMK-OT2016-FV1";
        rockchip,camera-module-lens-name = "default";
        port {
            ov13855_dphy0_out: endpoint {
                remote-endpoint = <&mipi_in_dphy0_ov13855>;
                data-lanes = <1 2 3 4>;
            };
        };
    };
};

&csi2_dphy0_hw {
    status = "okay";
};

&csi2_dphy0 {
    status = "okay";

    ports {
        #address-cells = <1>;
        #size-cells = <0>;
        port@0 {
            reg = <0>;

            mipi_in_dphy0_ov13855: endpoint@1 {
                reg = <1>;
                remote-endpoint = <&ov13855_dphy0_out>;
                data-lanes = <1 2 3 4>;
            };
        };

        port@1 {
            reg = <1>;

            csidphy0_out: endpoint@0 {
                reg = <0>;
                remote-endpoint = <&mipi2_csi2_input>;
            };
        };
    };

};

&mipi2_csi2 {
    status = "okay";

    ports {
        #address-cells = <1>;
        #size-cells = <0>;
        port@0 {
            reg = <0>;

            mipi2_csi2_input: endpoint@1 {
                reg = <1>;
                remote-endpoint = <&csidphy0_out>;
            };
        };
        port@1 {
            reg = <1>;

            mipi2_csi2_output: endpoint@0 {
                reg = <0>;
                remote-endpoint = <&cif_mipi_in2>;
            };
        };
    };
};

&rkcif_mipi_lvds2 {
    status = "okay";

    port {
        cif_mipi_in2: endpoint {
            remote-endpoint = <&mipi2_csi2_output>;
        };
    };
};

&rkcif_mipi_lvds2_sditf {
    status = "okay";

    port {
        mipi_lvds_sditf: endpoint {
            remote-endpoint = <&isp0_vir0>;
        };
    };
};


&rkisp0 {
    status = "okay";
};

&isp0_mmu {
    status = "okay";
};


&rkisp0_vir0 {
    status = "okay";
    port {
        #address-cells = <1>;
        #size-cells = <0>;
        isp0_vir0: endpoint@0 {
            reg = <0>;
            remote-endpoint = <&mipi_lvds_sditf>;
        };
    };
};

&pinctrl {
    cam {
        mipidphy0_pwr: mipidphy0-pwr {
            rockchip,pins =
            /* camera power en */
            <1 RK_PB2 RK_FUNC_GPIO &pcfg_pull_none>;
        };

        pwdn_gpio: pwdn-gpio {
            rockchip,pins =
            /* camera power en */
            <1 RK_PA2 RK_FUNC_GPIO &pcfg_pull_down_drv_level_15>;
        };
    };
};

上面DTS拓扑图如下：

+------------------+      +-------------+     +------------+     +------------------+     +--------+
|  camera sensor   |  --> | csi2_dphy0  | --> | mipi2_csi2 | --> | rkcif_mipi_lvds2 | --> | rkisp  |
+------------------+      +-------------+     +------------+     +------------------+     +--------+

其中camera sensor是设备厂商需要开发的，其它的驱动Rockchip平台提供。

29.1.1 csi2_dphy0

功能: 该模块负责 MIPI D-PHY (Physical Layer) 的管理。它处理从传感器 (例如 ov13855 和 os04a10) 发送来的 MIPI 数据流，将这些信号转换为可以被 MIPI CSI-2 接收器处理的电信号。这是从摄像头传感器到处理器传输数据的物理层。
管理 D-PHY 通道的配置，包括数据通道的初始化、同步等。
处理数据的低层物理传输，将其传递给上层模块（比如 MIPI CSI-2 接口）。

驱动代码是： kernel/drivers/phy/rockchip/phy-rockchip-csi2-dphy.c

29.1.2 mipi2_csi2

功能: 该模块负责 MIPI CSI-2 协议层的数据接收。它接收从 D-PHY 层传递来的数据包（视频流），解包 CSI-2 帧并传递给系统中下游的处理器或图像信号处理器 (ISP)。此驱动类似与网络中的MAC层，把DPHY物理信号转换成相对应格式视频数据。
负责 MIPI CSI-2 接口的初始化和配置，确保能够正确解包视频帧。
从 D-PHY 接收数据包，将其处理后传递给下游的视频处理单元或 ISP。

驱动代码是： kernel/drivers/media/platform/rockchip/cif/mipi-csi2.c

29.2 上电时序

不同 Sensor 对上电时序要求不同，例如可能很大部分的 OV Sensor 对时序要求不严格，只要 mclk、vdd、reset 和 powerdown 状态是对的、就能正确进行 I2C 通讯并输出图片，而不用关心上电的先后顺序及延时。但还是有小部分 Sensor 对上电要求非常严格，例如 OV13855 必须严格按时序上电。

static int __ov13855_power_on(struct ov13855 *ov13855)
{
	int ret;
	u32 delay_us;
	struct device *dev = &ov13855->client->dev;

	if (!IS_ERR(ov13855->power_gpio))
		gpiod_set_value_cansleep(ov13855->power_gpio, 1);

	usleep_range(1000, 2000);

	if (!IS_ERR_OR_NULL(ov13855->pins_default)) {
		ret = pinctrl_select_state(ov13855->pinctrl,
					   ov13855->pins_default);
		if (ret < 0)
			dev_err(dev, "could not set pins\n");
	}
	ret = clk_set_rate(ov13855->xvclk, OV13855_XVCLK_FREQ);
	if (ret < 0)
		dev_warn(dev, "Failed to set xvclk rate (24MHz)\n");
	if (clk_get_rate(ov13855->xvclk) != OV13855_XVCLK_FREQ)
		dev_warn(dev, "xvclk mismatched, modes are based on 24MHz\n");
	ret = clk_prepare_enable(ov13855->xvclk);
	if (ret < 0) {
		dev_err(dev, "Failed to enable xvclk\n");
		return ret;
	}
	if (!IS_ERR(ov13855->reset_gpio))
		gpiod_set_value_cansleep(ov13855->reset_gpio, 0);

	ret = regulator_bulk_enable(OV13855_NUM_SUPPLIES, ov13855->supplies);
	if (ret < 0) {
		dev_err(dev, "Failed to enable regulators\n");
		goto disable_clk;
	}

	if (!IS_ERR(ov13855->reset_gpio))
		gpiod_set_value_cansleep(ov13855->reset_gpio, 1);

	usleep_range(5000, 6000);
	if (!IS_ERR(ov13855->pwdn_gpio))
		gpiod_set_value_cansleep(ov13855->pwdn_gpio, 1);

	/* 8192 cycles prior to first SCCB transaction */
	delay_us = ov13855_cal_delay(8192);
	usleep_range(delay_us * 2, delay_us * 3);

	return 0;

disable_clk:
	clk_disable_unprepare(ov13855->xvclk);

	return ret;
}

在.probe()阶段会去尝试读取 chip id，如 ov13855 的 ov13855_check_sensor_id() ，如果能够正确读取到chip id，一般就认为上电时序正确，Sensor 能够正常进行 i2c 通信。

29.3 注册 V4L2 子设备

V4L2 框架是 Linux 内核中处理视频设备的核心模块。OV13855 作为 V4L2 的子设备，需要在驱动中注册并实现相应的接口。

static int ov13855_probe(struct i2c_client *client,
			 const struct i2c_device_id *id)
{
	struct device *dev = &client->dev;
	struct device_node *node = dev->of_node;
	struct ov13855 *ov13855;
	struct v4l2_subdev *sd;
	char facing[2];
	int ret;

	dev_info(dev, "driver version: %02x.%02x.%02x",
		DRIVER_VERSION >> 16,
		(DRIVER_VERSION & 0xff00) >> 8,
		DRIVER_VERSION & 0x00ff);

	ov13855 = devm_kzalloc(dev, sizeof(*ov13855), GFP_KERNEL);
	if (!ov13855)
		return -ENOMEM;

	ret = of_property_read_u32(node, RKMODULE_CAMERA_MODULE_INDEX,
				   &ov13855->module_index);
	ret |= of_property_read_string(node, RKMODULE_CAMERA_MODULE_FACING,
				       &ov13855->module_facing);
	ret |= of_property_read_string(node, RKMODULE_CAMERA_MODULE_NAME,
				       &ov13855->module_name);
	ret |= of_property_read_string(node, RKMODULE_CAMERA_LENS_NAME,
				       &ov13855->len_name);
	if (ret) {
		dev_err(dev, "could not get module information!\n");
		return -EINVAL;
	}

	ov13855->client = client;
	ov13855->cur_mode = &supported_modes[0];

	ov13855->xvclk = devm_clk_get(dev, "xvclk");
	if (IS_ERR(ov13855->xvclk)) {
		dev_err(dev, "Failed to get xvclk\n");
		return -EINVAL;
	}

	ov13855->power_gpio = devm_gpiod_get(dev, "power", GPIOD_OUT_LOW);
	if (IS_ERR(ov13855->power_gpio))
		dev_warn(dev, "Failed to get power-gpios, maybe no use\n");

	ov13855->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
	if (IS_ERR(ov13855->reset_gpio))
		dev_warn(dev, "Failed to get reset-gpios\n");

	ov13855->pwdn_gpio = devm_gpiod_get(dev, "pwdn", GPIOD_OUT_LOW);
	if (IS_ERR(ov13855->pwdn_gpio))
		dev_warn(dev, "Failed to get pwdn-gpios\n");

	ret = ov13855_configure_regulators(ov13855);
	if (ret) {
		dev_err(dev, "Failed to get power regulators\n");
		return ret;
	}

	ov13855->pinctrl = devm_pinctrl_get(dev);
	if (!IS_ERR(ov13855->pinctrl)) {
		ov13855->pins_default =
			pinctrl_lookup_state(ov13855->pinctrl,
					     OF_CAMERA_PINCTRL_STATE_DEFAULT);
		if (IS_ERR(ov13855->pins_default))
			dev_err(dev, "could not get default pinstate\n");

		ov13855->pins_sleep =
			pinctrl_lookup_state(ov13855->pinctrl,
					     OF_CAMERA_PINCTRL_STATE_SLEEP);
		if (IS_ERR(ov13855->pins_sleep))
			dev_err(dev, "could not get sleep pinstate\n");
	}

	mutex_init(&ov13855->mutex);

	sd = &ov13855->subdev;
	v4l2_i2c_subdev_init(sd, client, &ov13855_subdev_ops);
	ret = ov13855_initialize_controls(ov13855);
	if (ret)
		goto err_destroy_mutex;

	ret = __ov13855_power_on(ov13855);
	if (ret)
		goto err_free_handler;

	usleep_range(25000, 30000);

	ret = ov13855_check_sensor_id(ov13855, client);
	if (ret)
		goto err_power_off;

#ifdef CONFIG_VIDEO_V4L2_SUBDEV_API
	sd->internal_ops = &ov13855_internal_ops;
	sd->flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
#endif
#if defined(CONFIG_MEDIA_CONTROLLER)
	ov13855->pad.flags = MEDIA_PAD_FL_SOURCE;
	sd->entity.function = MEDIA_ENT_F_CAM_SENSOR;
	ret = media_entity_pads_init(&sd->entity, 1, &ov13855->pad);
	if (ret < 0)
		goto err_power_off;
#endif

	memset(facing, 0, sizeof(facing));
	if (strcmp(ov13855->module_facing, "back") == 0)
		facing[0] = 'b';
	else
		facing[0] = 'f';

	snprintf(sd->name, sizeof(sd->name), "m%02d_%s_%s %s",
		 ov13855->module_index, facing,
		 OV13855_NAME, dev_name(sd->dev));
	ret = v4l2_async_register_subdev_sensor_common(sd);
	if (ret) {
		dev_err(dev, "v4l2 async register subdev failed\n");
		goto err_clean_entity;
	}

	pm_runtime_set_active(dev);
	pm_runtime_enable(dev);
	pm_runtime_idle(dev);

	return 0;

err_clean_entity:
#if defined(CONFIG_MEDIA_CONTROLLER)
	media_entity_cleanup(&sd->entity);
#endif
err_power_off:
	__ov13855_power_off(ov13855);
err_free_handler:
	v4l2_ctrl_handler_free(&ov13855->ctrl_handler);
err_destroy_mutex:
	mutex_destroy(&ov13855->mutex);

	return ret;
}

在.probe函数里，有调用v4l2_i2c_subdev_init注册V4L2子设备，接着就是初始I2C参数及读取camera id。

29.4 实现 V4L2 接口

实现V4L2必要的接口函数，如下：

29.4.1 电源管理

static const struct dev_pm_ops ov13855_pm_ops = {
	SET_RUNTIME_PM_OPS(ov13855_runtime_suspend,
			   ov13855_runtime_resume, NULL)
};

SET_RUNTIME_PM_OPS：这个宏定义了运行时电源管理（runtime power management）相关的操作，包括：

ov13855_runtime_suspend：当设备进入空闲状态时调用，用于降低功耗，比如关闭摄像头的电源或时钟。
ov13855_runtime_resume：当设备重新被访问时调用，用于恢复摄像头的电源和时钟，重新使其工作。

29.4.2 v4l2_subdev_core_ops

static const struct v4l2_subdev_core_ops ov13855_core_ops = {
	.s_power = ov13855_s_power,
	.ioctl   = ov13855_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl32 = ov13855_compat_ioctl32,
#endif
};

v4l2_subdev_core_ops：定义核心操作，涵盖子设备的一些通用功能，如电源控制和自定义 I/O 操作。

ov13855_s_power：用于控制摄像头传感器的电源。根据参数 on，可以开启或关闭摄像头电源（或复位）。
ov13855_ioctl：用于处理应用程序通过 ioctl 系统调用发送的自定义命令。它可以扩展标准的 V4L2 控制功能，处理额外的摄像头配置操作。
ov13855_compat_ioctl32：用于 32-bit 用户空间应用和 64-bit 内核之间的兼容处理，确保在 64-bit 系统上可以正常处理 32-bit 应用的 ioctl 请求。

29.4.3 v4l2_subdev_video_ops

static const struct v4l2_subdev_video_ops ov13855_video_ops = {
	.s_stream         = ov13855_s_stream,
	.g_frame_interval = ov13855_g_frame_interval,
};

v4l2_subdev_video_ops：定义视频相关的操作，主要用于处理摄像头传感器的视频流和帧控制。

ov13855_s_stream：用于开启或关闭视频流。当这个函数被调用时，摄像头开始传输图像数据或者停止传输。
ov13855_g_frame_interval：用于获取视频流的帧间隔（帧率）。这可以帮助上层应用了解摄像头的输出帧率。

29.4.4 v4l2_subdev_pad_ops

static const struct v4l2_subdev_pad_ops ov13855_pad_ops = {
	.enum_mbus_code      = ov13855_enum_mbus_code,
	.enum_frame_size     = ov13855_enum_frame_sizes,
	.enum_frame_interval = ov13855_enum_frame_interval,
	.get_fmt             = ov13855_get_fmt,
	.set_fmt             = ov13855_set_fmt,
	.get_selection       = ov13855_get_selection,
	.get_mbus_config     = ov13855_g_mbus_config,
};

v4l2_subdev_pad_ops：用于配置视频数据的传输格式、分辨率和相关参数的操作集。此类操作允许配置摄像头传感器的输出格式和尺寸。

ov13855_enum_mbus_code：枚举支持的媒体总线格式（比如 Bayer 格式的 RAW 数据类型）。这有助于应用程序知道摄像头支持哪些数据格式。
ov13855_enum_frame_sizes：枚举摄像头支持的帧尺寸（分辨率），比如 4208x3120。
ov13855_enum_frame_interval：枚举支持的帧间隔（帧率）。
ov13855_get_fmt：获取当前的帧格式（如分辨率和数据类型）。
ov13855_set_fmt：设置帧格式，通常包括分辨率、数据类型等信息。
ov13855_get_selection：获取当前的图像裁剪窗口或其他选择区域的参数。
ov13855_g_mbus_config：获取媒体总线配置，比如 MIPI CSI-2 的通道配置、数据速率等。

29.4.5 v4l2_subdev_ops

static const struct v4l2_subdev_ops ov13855_subdev_ops = {
	.core	= &ov13855_core_ops,
	.video	= &ov13855_video_ops,
	.pad	= &ov13855_pad_ops,
};

v4l2_subdev_ops：整合所有不同操作集的接口定义。它将核心操作（core_ops）、视频流操作（video_ops）和数据格式操作（pad_ops）统一到一个子设备操作集，以便 V4L2 框架能够调用合适的接口函数。

29.5 数据格式

OV13855 输出的原始（RAW）数据格式通常是 Bayer 格式，这是图像传感器常用的 RAW 格式之一。具体来说，OV13855 支持 10-bit Bayer 格式，输出的 Bayer 数据格式通常为 BGGR，也就是在图像传感器上的颜色滤波阵列排列顺序是蓝（Blue）、绿（Green）、绿（Green）、红（Red）。

#define OV13855_LANES			4
#define OV13855_BITS_PER_SAMPLE		10

static const struct ov13855_mode supported_modes[] = {
	{
		.width = 4224,
		.height = 3136,
		.max_fps = {
			.numerator = 10000,
			.denominator = 300000,
		},
		.exp_def = 0x0800,
		.hts_def = 0x0462,
		.vts_def = 0x0c8e,
		.bpp = 10,
		.reg_list = ov13855_4224x3136_30fps_regs,
		.link_freq_idx = 0,
	},
#ifdef DEBUG
	{
		.width = 2112,
		.height = 1568,
		.max_fps = {
			.numerator = 10000,
			.denominator = 600000,
		},
		.exp_def = 0x0400,
		.hts_def = 0x0462,
		.vts_def = 0x0c89,
		.bpp = 10,
		.reg_list = ov13855_2112x1568_60fps_regs,
		.link_freq_idx = 1,
	},
	{
		.width = 4224,
		.height = 3136,
		.max_fps = {
			.numerator = 10000,
			.denominator = 150000,
		},
		.exp_def = 0x0800,
		.hts_def = 0x08c4,
		.vts_def = 0x0c8e,
		.bpp = 10,
		.reg_list = ov13855_4224x3136_15fps_regs,
		.link_freq_idx = 0,
	},
#endif
};

29.5.1 数据传输

(1) MIPI CSI 数据传输

OV13855 是一款使用 MIPI CSI-2 接口的摄像头传感器。MIPI CSI（Camera Serial Interface）是一种高速串行数据传输接口，通常用于传输摄像头的原始图像数据。在数据传输过程中，OV13855 会将其捕获的图像数据（通常是 Bayer 格式的 RAW 数据）通过 MIPI 通道传输到主处理器mipi2_csi2节点(Rockchip提供此V4L2子设备，代码在kernel/drivers/media/platform/rockchip/cif/mipi-csi2.c)。

(2) ISP图像信号处理

虽然 OV13855 驱动本身负责数据的传输，但通常摄像头传感器输出的 Bayer RAW 数据需要通过 ISP 进行进一步处理。Rockchip ISP驱动代码在： kernel/drivers/media/platform/rockchip/isp/*, ISP 的功能包括：

Demosaicing：将 Bayer 格式的原始数据转换为 RGB 或 YUV 格式的图像。
颜色校正和降噪：这些处理可以显著提高图像质量。

ISP 通常位于 SoC 中，并由平台的 ISP 驱动负责控制。OV13855 驱动与平台的 ISP 驱动之间通过 V4L2 框架进行数据和控制的交互。

Rockchip ISP驱动框图如下：

(3) 设备节点

在Neardi RK3588设备，有如下视频节点：

neardi@LPA3588:~$ v4l2-ctl --list-devices
rk_hdmirx (fdee0000.hdmirx-controller):
        /dev/video40

rkisp-statistics (platform: rkisp):
        /dev/video29
        /dev/video30
        /dev/video38
        /dev/video39

rkcif-mipi-lvds2 (platform:rkcif):
        /dev/media0
        /dev/media1

rkcif (platform:rkcif-mipi-lvds4):
        /dev/video11
        /dev/video12
        /dev/video13
        /dev/video14
        /dev/video15
        /dev/video16
        /dev/video17
        /dev/video18
        /dev/video19
        /dev/video20
        /dev/video21

rkisp_mainpath (platform:rkisp0-vir0):
        /dev/video22
        /dev/video23
        /dev/video24
        /dev/video25
        /dev/video26
        /dev/video27
        /dev/video28
        /dev/media2

rkisp_mainpath (platform:rkisp1-vir1):
        /dev/video31
        /dev/video32
        /dev/video33
        /dev/video34
        /dev/video35
        /dev/video36
        /dev/video37
        /dev/media3

上面不同的视频节点，视频数据处理算法不同。在rkisp_mainpath里的节点，是经过ISP算法之后的数据，如下：

29.6 Debug驱动

(1). 安装V4L2工具v4l-utils

v4l-utils 包在 Ubuntu 系统下，可通过 apt 工具直接安装，如下，

sudo apt-get install v4l-utils

这样可以抓取不同视频节点的数据，如下：

neardi@LPA3588:~$ v4l2-ctl -d /dev/video31  --set-fmt-video=width=1280,height=720,pixelformat=NV12  --stream-mmap=3  --stream-skip=3  --stream-to=./test.out  --stream-count=1  --stream-poll
<<<<
neardi@LPA3588:~$ ls -lh test.out
-rw-rw-r-- 1 neardi neardi 1.4M Oct 12 07:07 test.out

(2). 使用media-ctl查看拓扑结构

media-ctl 是 v4l-utils 包中的一个工具，主要用来查看、配置 Media Framework 的各Entity的信息，如格
式、裁剪、链接使能等。应用该工具可以更灵活地拓展Camera功能。对于普通的应用场景，用户不必去配置具体的Entity信息，直接使用默认的就可以。

neardi@LPA3588:~$ media-ctl -p -d /dev/media1
Media controller API version 5.10.110

Media device information
------------------------
driver          rkcif
model           rkcif-mipi-lvds4
serial
bus info
hw revision     0x0
driver version  5.10.110

Device topology
- entity 1: stream_cif_mipi_id0 (1 pad, 11 links)
            type Node subtype V4L flags 0
            device node name /dev/video11
        pad0: Sink
                <- "rockchip-mipi-csi2":1 [ENABLED]
                <- "rockchip-mipi-csi2":2 []
                <- "rockchip-mipi-csi2":3 []
                <- "rockchip-mipi-csi2":4 []
                <- "rockchip-mipi-csi2":5 []
                <- "rockchip-mipi-csi2":6 []
                <- "rockchip-mipi-csi2":7 []
                <- "rockchip-mipi-csi2":8 []
                <- "rockchip-mipi-csi2":9 []
                <- "rockchip-mipi-csi2":10 []
                <- "rockchip-mipi-csi2":11 []

- entity 5: stream_cif_mipi_id1 (1 pad, 11 links)
            type Node subtype V4L flags 0
            device node name /dev/video12
        pad0: Sink
                <- "rockchip-mipi-csi2":1 []
                <- "rockchip-mipi-csi2":2 [ENABLED]
                <- "rockchip-mipi-csi2":3 []
                <- "rockchip-mipi-csi2":4 []
                <- "rockchip-mipi-csi2":5 []
                <- "rockchip-mipi-csi2":6 []
                <- "rockchip-mipi-csi2":7 []
                <- "rockchip-mipi-csi2":8 []
                <- "rockchip-mipi-csi2":9 []
                <- "rockchip-mipi-csi2":10 []
                <- "rockchip-mipi-csi2":11 []

- entity 9: stream_cif_mipi_id2 (1 pad, 11 links)
            type Node subtype V4L flags 0
            device node name /dev/video13
        pad0: Sink
                <- "rockchip-mipi-csi2":1 []
                <- "rockchip-mipi-csi2":2 []
                <- "rockchip-mipi-csi2":3 [ENABLED]
                <- "rockchip-mipi-csi2":4 []
                <- "rockchip-mipi-csi2":5 []
                <- "rockchip-mipi-csi2":6 []
                <- "rockchip-mipi-csi2":7 []
                <- "rockchip-mipi-csi2":8 []
                <- "rockchip-mipi-csi2":9 []
                <- "rockchip-mipi-csi2":10 []
                <- "rockchip-mipi-csi2":11 []

- entity 13: stream_cif_mipi_id3 (1 pad, 11 links)
             type Node subtype V4L flags 0
             device node name /dev/video14
        pad0: Sink
                <- "rockchip-mipi-csi2":1 []
                <- "rockchip-mipi-csi2":2 []
                <- "rockchip-mipi-csi2":3 []
                <- "rockchip-mipi-csi2":4 [ENABLED]
                <- "rockchip-mipi-csi2":5 []
                <- "rockchip-mipi-csi2":6 []
                <- "rockchip-mipi-csi2":7 []
                <- "rockchip-mipi-csi2":8 []
                <- "rockchip-mipi-csi2":9 []
                <- "rockchip-mipi-csi2":10 []
                <- "rockchip-mipi-csi2":11 []

- entity 17: rkcif_scale_ch0 (1 pad, 11 links)
             type Node subtype V4L flags 0
             device node name /dev/video15
        pad0: Sink
                <- "rockchip-mipi-csi2":1 []
                <- "rockchip-mipi-csi2":2 []
                <- "rockchip-mipi-csi2":3 []
                <- "rockchip-mipi-csi2":4 []
                <- "rockchip-mipi-csi2":5 [ENABLED]
                <- "rockchip-mipi-csi2":6 []
                <- "rockchip-mipi-csi2":7 []
                <- "rockchip-mipi-csi2":8 []
                <- "rockchip-mipi-csi2":9 []
                <- "rockchip-mipi-csi2":10 []
                <- "rockchip-mipi-csi2":11 []

- entity 21: rkcif_scale_ch1 (1 pad, 11 links)
             type Node subtype V4L flags 0
             device node name /dev/video16
        pad0: Sink
                <- "rockchip-mipi-csi2":1 []
                <- "rockchip-mipi-csi2":2 []
                <- "rockchip-mipi-csi2":3 []
                <- "rockchip-mipi-csi2":4 []
                <- "rockchip-mipi-csi2":5 []
                <- "rockchip-mipi-csi2":6 [ENABLED]
                <- "rockchip-mipi-csi2":7 []
                <- "rockchip-mipi-csi2":8 []
                <- "rockchip-mipi-csi2":9 []
                <- "rockchip-mipi-csi2":10 []
                <- "rockchip-mipi-csi2":11 []

- entity 25: rkcif_scale_ch2 (1 pad, 11 links)
             type Node subtype V4L flags 0
             device node name /dev/video17
        pad0: Sink
                <- "rockchip-mipi-csi2":1 []
                <- "rockchip-mipi-csi2":2 []
                <- "rockchip-mipi-csi2":3 []
                <- "rockchip-mipi-csi2":4 []
                <- "rockchip-mipi-csi2":5 []
                <- "rockchip-mipi-csi2":6 []
                <- "rockchip-mipi-csi2":7 [ENABLED]
                <- "rockchip-mipi-csi2":8 []
                <- "rockchip-mipi-csi2":9 []
                <- "rockchip-mipi-csi2":10 []
                <- "rockchip-mipi-csi2":11 []

- entity 29: rkcif_scale_ch3 (1 pad, 11 links)
             type Node subtype V4L flags 0
             device node name /dev/video18
        pad0: Sink
                <- "rockchip-mipi-csi2":1 []
                <- "rockchip-mipi-csi2":2 []
                <- "rockchip-mipi-csi2":3 []
                <- "rockchip-mipi-csi2":4 []
                <- "rockchip-mipi-csi2":5 []
                <- "rockchip-mipi-csi2":6 []
                <- "rockchip-mipi-csi2":7 []
                <- "rockchip-mipi-csi2":8 [ENABLED]
                <- "rockchip-mipi-csi2":9 []
                <- "rockchip-mipi-csi2":10 []
                <- "rockchip-mipi-csi2":11 []

- entity 33: rkcif_tools_id0 (1 pad, 11 links)
             type Node subtype V4L flags 0
             device node name /dev/video19
        pad0: Sink
                <- "rockchip-mipi-csi2":1 []
                <- "rockchip-mipi-csi2":2 []
                <- "rockchip-mipi-csi2":3 []
                <- "rockchip-mipi-csi2":4 []
                <- "rockchip-mipi-csi2":5 []
                <- "rockchip-mipi-csi2":6 []
                <- "rockchip-mipi-csi2":7 []
                <- "rockchip-mipi-csi2":8 []
                <- "rockchip-mipi-csi2":9 [ENABLED]
                <- "rockchip-mipi-csi2":10 []
                <- "rockchip-mipi-csi2":11 []

- entity 37: rkcif_tools_id1 (1 pad, 11 links)
             type Node subtype V4L flags 0
             device node name /dev/video20
        pad0: Sink
                <- "rockchip-mipi-csi2":1 []
                <- "rockchip-mipi-csi2":2 []
                <- "rockchip-mipi-csi2":3 []
                <- "rockchip-mipi-csi2":4 []
                <- "rockchip-mipi-csi2":5 []
                <- "rockchip-mipi-csi2":6 []
                <- "rockchip-mipi-csi2":7 []
                <- "rockchip-mipi-csi2":8 []
                <- "rockchip-mipi-csi2":9 []
                <- "rockchip-mipi-csi2":10 [ENABLED]
                <- "rockchip-mipi-csi2":11 []

- entity 41: rkcif_tools_id2 (1 pad, 11 links)
             type Node subtype V4L flags 0
             device node name /dev/video21
        pad0: Sink
                <- "rockchip-mipi-csi2":1 []
                <- "rockchip-mipi-csi2":2 []
                <- "rockchip-mipi-csi2":3 []
                <- "rockchip-mipi-csi2":4 []
                <- "rockchip-mipi-csi2":5 []
                <- "rockchip-mipi-csi2":6 []
                <- "rockchip-mipi-csi2":7 []
                <- "rockchip-mipi-csi2":8 []
                <- "rockchip-mipi-csi2":9 []
                <- "rockchip-mipi-csi2":10 []
                <- "rockchip-mipi-csi2":11 [ENABLED]

- entity 45: rockchip-mipi-csi2 (12 pads, 122 links)
             type V4L2 subdev subtype Unknown flags 0
             device node name /dev/v4l-subdev2
        pad0: Sink
                [fmt:SBGGR10_1X10/4224x3136 field:none
                 crop.bounds:(0,0)/4224x3136
                 crop:(0,0)/4224x3136]
                <- "rockchip-csi2-dphy3":1 [ENABLED]
        pad1: Source
                -> "stream_cif_mipi_id0":0 [ENABLED]
                -> "stream_cif_mipi_id1":0 []
                -> "stream_cif_mipi_id2":0 []
                -> "stream_cif_mipi_id3":0 []
                -> "rkcif_scale_ch0":0 []
                -> "rkcif_scale_ch1":0 []
                -> "rkcif_scale_ch2":0 []
                -> "rkcif_scale_ch3":0 []
                -> "rkcif_tools_id0":0 []
                -> "rkcif_tools_id1":0 []
                -> "rkcif_tools_id2":0 []
        pad2: Source
                -> "stream_cif_mipi_id0":0 []
                -> "stream_cif_mipi_id1":0 [ENABLED]
                -> "stream_cif_mipi_id2":0 []
                -> "stream_cif_mipi_id3":0 []
                -> "rkcif_scale_ch0":0 []
                -> "rkcif_scale_ch1":0 []
                -> "rkcif_scale_ch2":0 []
                -> "rkcif_scale_ch3":0 []
                -> "rkcif_tools_id0":0 []
                -> "rkcif_tools_id1":0 []
                -> "rkcif_tools_id2":0 []
        pad3: Source
                -> "stream_cif_mipi_id0":0 []
                -> "stream_cif_mipi_id1":0 []
                -> "stream_cif_mipi_id2":0 [ENABLED]
                -> "stream_cif_mipi_id3":0 []
                -> "rkcif_scale_ch0":0 []
                -> "rkcif_scale_ch1":0 []
                -> "rkcif_scale_ch2":0 []
                -> "rkcif_scale_ch3":0 []
                -> "rkcif_tools_id0":0 []
                -> "rkcif_tools_id1":0 []
                -> "rkcif_tools_id2":0 []
        pad4: Source
                -> "stream_cif_mipi_id0":0 []
                -> "stream_cif_mipi_id1":0 []
                -> "stream_cif_mipi_id2":0 []
                -> "stream_cif_mipi_id3":0 [ENABLED]
                -> "rkcif_scale_ch0":0 []
                -> "rkcif_scale_ch1":0 []
                -> "rkcif_scale_ch2":0 []
                -> "rkcif_scale_ch3":0 []
                -> "rkcif_tools_id0":0 []
                -> "rkcif_tools_id1":0 []
                -> "rkcif_tools_id2":0 []
        pad5: Source
                -> "stream_cif_mipi_id0":0 []
                -> "stream_cif_mipi_id1":0 []
                -> "stream_cif_mipi_id2":0 []
                -> "stream_cif_mipi_id3":0 []
                -> "rkcif_scale_ch0":0 [ENABLED]
                -> "rkcif_scale_ch1":0 []
                -> "rkcif_scale_ch2":0 []
                -> "rkcif_scale_ch3":0 []
                -> "rkcif_tools_id0":0 []
                -> "rkcif_tools_id1":0 []
                -> "rkcif_tools_id2":0 []
        pad6: Source
                -> "stream_cif_mipi_id0":0 []
                -> "stream_cif_mipi_id1":0 []
                -> "stream_cif_mipi_id2":0 []
                -> "stream_cif_mipi_id3":0 []
                -> "rkcif_scale_ch0":0 []
                -> "rkcif_scale_ch1":0 [ENABLED]
                -> "rkcif_scale_ch2":0 []
                -> "rkcif_scale_ch3":0 []
                -> "rkcif_tools_id0":0 []
                -> "rkcif_tools_id1":0 []
                -> "rkcif_tools_id2":0 []
        pad7: Source
                -> "stream_cif_mipi_id0":0 []
                -> "stream_cif_mipi_id1":0 []
                -> "stream_cif_mipi_id2":0 []
                -> "stream_cif_mipi_id3":0 []
                -> "rkcif_scale_ch0":0 []
                -> "rkcif_scale_ch1":0 []
                -> "rkcif_scale_ch2":0 [ENABLED]
                -> "rkcif_scale_ch3":0 []
                -> "rkcif_tools_id0":0 []
                -> "rkcif_tools_id1":0 []
                -> "rkcif_tools_id2":0 []
        pad8: Source
                -> "stream_cif_mipi_id0":0 []
                -> "stream_cif_mipi_id1":0 []
                -> "stream_cif_mipi_id2":0 []
                -> "stream_cif_mipi_id3":0 []
                -> "rkcif_scale_ch0":0 []
                -> "rkcif_scale_ch1":0 []
                -> "rkcif_scale_ch2":0 []
                -> "rkcif_scale_ch3":0 [ENABLED]
                -> "rkcif_tools_id0":0 []
                -> "rkcif_tools_id1":0 []
                -> "rkcif_tools_id2":0 []
        pad9: Source
                -> "stream_cif_mipi_id0":0 []
                -> "stream_cif_mipi_id1":0 []
                -> "stream_cif_mipi_id2":0 []
                -> "stream_cif_mipi_id3":0 []
                -> "rkcif_scale_ch0":0 []
                -> "rkcif_scale_ch1":0 []
                -> "rkcif_scale_ch2":0 []
                -> "rkcif_scale_ch3":0 []
                -> "rkcif_tools_id0":0 [ENABLED]
                -> "rkcif_tools_id1":0 []
                -> "rkcif_tools_id2":0 []
        pad10: Source
                -> "stream_cif_mipi_id0":0 []
                -> "stream_cif_mipi_id1":0 []
                -> "stream_cif_mipi_id2":0 []
                -> "stream_cif_mipi_id3":0 []
                -> "rkcif_scale_ch0":0 []
                -> "rkcif_scale_ch1":0 []
                -> "rkcif_scale_ch2":0 []
                -> "rkcif_scale_ch3":0 []
                -> "rkcif_tools_id0":0 []
                -> "rkcif_tools_id1":0 [ENABLED]
                -> "rkcif_tools_id2":0 []
        pad11: Source
                -> "stream_cif_mipi_id0":0 []
                -> "stream_cif_mipi_id1":0 []
                -> "stream_cif_mipi_id2":0 []
                -> "stream_cif_mipi_id3":0 []
                -> "rkcif_scale_ch0":0 []
                -> "rkcif_scale_ch1":0 []
                -> "rkcif_scale_ch2":0 []
                -> "rkcif_scale_ch3":0 []
                -> "rkcif_tools_id0":0 []
                -> "rkcif_tools_id1":0 []
                -> "rkcif_tools_id2":0 [ENABLED]

- entity 58: rockchip-csi2-dphy3 (2 pads, 2 links)
             type V4L2 subdev subtype Unknown flags 0
             device node name /dev/v4l-subdev3
        pad0: Sink
                [fmt:SBGGR10_1X10/4224x3136@10000/300000 field:none
                 crop.bounds:(0,0)/4224x3136]
                <- "m01_f_ov13855 2-0010":0 [ENABLED]
        pad1: Source
                -> "rockchip-mipi-csi2":0 [ENABLED]

- entity 63: m01_f_ov13855 2-0010 (1 pad, 1 link)
             type V4L2 subdev subtype Sensor flags 0
             device node name /dev/v4l-subdev4
        pad0: Source
                [fmt:SBGGR10_1X10/4224x3136@10000/300000 field:none
                 crop.bounds:(0,0)/4224x3136]
                -> "rockchip-csi2-dphy3":0 [ENABLED]

(3). 抓取Raw图

RKISP1的MP节点可以抓取Raw图，此时ISP是by-pass状态，不对数据做调制。
示例，抓取 Sensor OV13855 输出的 Raw Bayer 原始数据。格式为 SBGGR10_1X10/4224x3136 大小为 4224x3136。

从 media-ctl -p 的输出可以看到，OV13855 传感器连接到了 rockchip-csi2-dphy3，然后通过 CSI2 接口连接到 rockchip-mipi-csi2。

设置输出格式：

media-ctl -d /dev/media1 --set-v4l2 '"m01_f_ov13855 2-0010":0[fmt:SBGGR10_1X10/4224x3136]'

选择合适的视频节点
输出中显示，stream_cif_mipi_id0、stream_cif_mipi_id1、stream_cif_mipi_id2 和 stream_cif_mipi_id3 代表不同的 MIPI 通道（/dev/video11, /dev/video12, /dev/video13, /dev/video14），可以使用其中之一来抓取原始数据。以 stream_cif_mipi_id0（/dev/video11）为例，它连接到 CSI2 的第一个 pad（pad1），已经启用。

可以通过 v4l2-ctl 命令从 /dev/video11 设备节点抓取原始数据：

neardi@LPA3588:~$ v4l2-ctl --device /dev/video11 --stream-mmap --stream-count=100 --stream-o=output.raw
                VIDIOC_REQBUFS returned -1 (Device or resource busy)

抓取失败，使用/dev/video12：

neardi@LPA3588:~$ v4l2-ctl --device /dev/video11 --stream-mmap --stream-count=100 --stream-to=output.raw
                VIDIOC_REQBUFS returned -1 (Device or resource busy)
neardi@LPA3588:~$ v4l2-ctl --device /dev/video12 --stream-mmap --stream-count=100 --stream-to=output.raw
<<<<<<<<<<<<<<<<<<<<<<<<<<<<< 29.94 fps, dropped buffers: 2
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< 29.94 fps
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< 29.95 fps
<<<<<<<<<<<
neardi@LPA3588:~$ ls output.raw -lh
-rw-rw-r-- 1 neardi neardi 1.6G Oct 12 07:59 output.raw

这个视频节点抓取成功。也可以把一帧RAW数据转换成一张图片，如下：

neardi@LPA3588:~$ ffmpeg -f rawvideo -pix_fmt gray16le -s 4224x3136 -i output.raw -frames:v 1 -loglevel debug output_image.png
ffmpeg version 4.2.7-0ubuntu0.1 Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 9 (Ubuntu 9.4.0-1ubuntu1~20.04.1)
  configuration: --prefix=/usr --extra-version=0ubuntu0.1 --toolchain=hardened --libdir=/usr/lib/aarch64-linux-gnu --incdir=/usr/include/aarch64-linux-gnu --arch=arm64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Splitting the commandline.
Reading option '-f' ... matched as option 'f' (force format) with argument 'rawvideo'.
Reading option '-pix_fmt' ... matched as option 'pix_fmt' (set pixel format) with argument 'gray16le'.
Reading option '-s' ... matched as option 's' (set frame size (WxH or abbreviation)) with argument '4224x3136'.
Reading option '-i' ... matched as input url with argument 'output.raw'.
Reading option '-frames:v' ... matched as option 'frames' (set the number of frames to output) with argument '1'.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument 'debug'.
Reading option 'output_image.png' ... matched as output url.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option loglevel (set logging level) with argument debug.
Successfully parsed a group of options.
Parsing a group of options: input url output.raw.
Applying option f (force format) with argument rawvideo.
Applying option pix_fmt (set pixel format) with argument gray16le.
Applying option s (set frame size (WxH or abbreviation)) with argument 4224x3136.
Successfully parsed a group of options.
Opening an input file: output.raw.
[rawvideo @ 0x55937f57b0] Opening 'output.raw' for reading
[file @ 0x55937c18f0] Setting default whitelist 'file,crypto'
[rawvideo @ 0x55937f57b0] Before avformat_find_stream_info() pos: 0 bytes read:32768 seeks:0 nb_streams:1
[rawvideo @ 0x55937f57b0] All info found
[rawvideo @ 0x55937f57b0] Estimating duration from bitrate, this may be inaccurate
[rawvideo @ 0x55937f57b0] After avformat_find_stream_info() pos: 26492928 bytes read:26492928 seeks:0 frames:1
Input #0, rawvideo, from 'output.raw':
  Duration: 00:00:00.52, start: 0.000000, bitrate: 5187426 kb/s
    Stream #0:0, 1, 1/25: Video: rawvideo, 1 reference frame (Y1[0][16] / 0x10003159), gray16le, 4224x3136, 0/1, 5298585 kb/s, 25 tbr, 25 tbn, 25 tbc
Successfully opened the file.
Parsing a group of options: output url output_image.png.
Applying option frames:v (set the number of frames to output) with argument 1.
Successfully parsed a group of options.
Opening an output file: output_image.png.
File 'output_image.png' already exists. Overwrite ? [y/N] y
Successfully opened the file.
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> png (native))
Press [q] to stop, [?] for help
cur_dts is invalid st:0 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
[rawvideo @ 0x55937ff9e0] PACKET SIZE: 26492928, STRIDE: 8448
detected 8 logical cores
[graph 0 input from stream 0:0 @ 0x5593806f40] Setting 'video_size' to value '4224x3136'
[graph 0 input from stream 0:0 @ 0x5593806f40] Setting 'pix_fmt' to value '30'
[graph 0 input from stream 0:0 @ 0x5593806f40] Setting 'time_base' to value '1/25'
[graph 0 input from stream 0:0 @ 0x5593806f40] Setting 'pixel_aspect' to value '0/1'
[graph 0 input from stream 0:0 @ 0x5593806f40] Setting 'sws_param' to value 'flags=2'
[graph 0 input from stream 0:0 @ 0x5593806f40] Setting 'frame_rate' to value '25/1'
[graph 0 input from stream 0:0 @ 0x5593806f40] w:4224 h:3136 pixfmt:gray16le tb:1/25 fr:25/1 sar:0/1 sws_param:flags=2
[format @ 0x5593807350] Setting 'pix_fmts' to value 'rgb24|rgba|rgb48be|rgba64be|pal8|gray|ya8|gray16be|ya16be|monob'
[auto_scaler_0 @ 0x5593808940] Setting 'flags' to value 'bicubic'
[auto_scaler_0 @ 0x5593808940] w:iw h:ih flags:'bicubic' interl:0
[format @ 0x5593807350] auto-inserting filter 'auto_scaler_0' between the filter 'Parsed_null_0' and the filter 'format'
[AVFilterGraph @ 0x55937c1600] query_formats: 4 queried, 2 merged, 1 already done, 0 delayed
[auto_scaler_0 @ 0x5593808940] picking gray16be out of 10 ref:gray16le alpha:0
[auto_scaler_0 @ 0x5593808940] w:4224 h:3136 fmt:gray16le sar:0/1 -> w:4224 h:3136 fmt:gray16be sar:0/1 flags:0x4
Output #0, image2, to 'output_image.png':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #0:0, 0, 1/25: Video: png, 1 reference frame, gray16be, 4224x3136, 0/1, q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc
    Metadata:
      encoder         : Lavc58.54.100 png
Clipping frame in rate conversion by 0.000008
No more output streams to write to, finishing.
[image2 @ 0x55937ffe10] Opening 'output_image.png' for writing
[file @ 0x5593ac26d0] Setting default whitelist 'file,crypto'
[AVIOContext @ 0x55937bed50] Statistics: 0 seeks, 83 writeouts
frame=    1 fps=0.5 q=-0.0 Lsize=N/A time=00:00:00.04 bitrate=N/A speed=0.0187x
video:21181kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Input file #0 (output.raw):
  Input stream #0:0 (video): 1 packets read (26492928 bytes); 1 frames decoded;
  Total: 1 packets (26492928 bytes) demuxed
Output file #0 (output_image.png):
  Output stream #0:0 (video): 1 frames encoded; 1 packets muxed (21689255 bytes);
  Total: 1 packets (21689255 bytes) muxed
1 frames successfully decoded, 0 decoding errors
[AVIOContext @ 0x55937bf320] Statistics: 26492928 bytes read, 0 seeks

(4). 打开调试开关

RKISP1或RKCIF驱动中都包含一些v4l2_dbg() log，通过命令可以打开 log 开关,如下。

root@LPA3588:~# echo 1 > /sys/module/video_rkcif/parameters/debug
root@LPA3588:~# ls /sys/module/video_rkcif/parameters/ -l
total 0
--w------- 1 root root 4096 Oct 12 08:13 clr_unready_dev
-rw-r--r-- 1 root root 4096 Oct 12 08:12 debug
-rw-r--r-- 1 root root 4096 Oct 12 08:13 debug_csi2
-r--r--r-- 1 root root 4096 Oct 12 08:13 version
root@LPA3588:~# cat /sys/module/video_rkcif/parameters/debug
1

打开 v4l2 相关的 log，比如 ioctl 调用。如下命令将 v4l2 相关 log 全部打开。

root@LPA3588:~# ls /sys/class/video4linux/video0/dev_debug
/sys/class/video4linux/video0/dev_debug
root@LPA3588:~# echo 1 > /sys/class/video4linux/video0/dev_debug
root@LPA3588:~# cat /sys/class/video4linux/video0/dev_debug
1

也可以分别只开一小部分的 log。如下Kernel宏定义了各个 bit 会 enable 哪些 log。将所需要的 log对应的bit 打开即可。这些宏定义在 kernel 头文件 include/media/v4l2-ioctl.h 中。

/* Just log the ioctl name + error code */
#define V4L2_DEV_DEBUG_IOCTL 0x01
/* Log the ioctl name arguments + error code */
#define V4L2_DEV_DEBUG_IOCTL_ARG 0x02
/* Log the file operations open, release, mmap and get_unmapped_area */
#define V4L2_DEV_DEBUG_FOP 0x04
/* Log the read and write file operations and the VIDIOC_(D)QBUF ioctls */
#define V4L2_DEV_DEBUG_STREAMING 0x08
/* Log poll() */
#define V4L2_DEV_DEBUG_POLL 0x10

29.7 总结

开发 Linux MIPI 摄像头驱动（如 OV13855）时，驱动的核心工作是配置摄像头传感器并通过 MIPI CSI 接口与主设备驱动协作。OV13855 驱动作为 V4L2 子设备，提供了丰富的接口供上层驱动和应用调用，包括电源管理、数据格式配置、视频流控制等。

主要步骤：

配置设备树，定义传感器的 GPIO、时钟和 MIPI 接口。
注册 V4L2 子设备并实现必要的操作接口。
实现 s_stream 和其他控制接口来控制摄像头的数据流。
通过 SoC 的 CSI 接口和 ISP 驱动完成数据的传输和处理。

通过这些步骤，驱动可以使摄像头传感器正常工作，图像数据能被正确传输、处理并提供给应用程序使用。