camera 模组驱动优化

因为项目比较多，平台支持的 camera 模组已经有 10 多个了，代码比较繁杂，就把 camera 模组端的驱动架构优化了一下。总的思路就是将公共的接口统一起来，减少代码的耦合度，建立新的公共接口文件 cam_core.c 和 cam_core.h。

一、基础数据结构

新建立的数据结构如下：

struct cam_info {struct i2c_client   *i2c_dev;  /* 指向模组的i2c从设备 */struct cam_priv     *priv;     /* 指向模组的操作接口 */struct v4l2_subdev  sd;        /* v4l2子设备 */uint32_t maxwidth;             /* 模组支持的最大分辨率 */uint32_t maxheight;uint32_t minwidth;             /* 模组支持的最小分辨率 */uint32_t minheight;/* current param used for each frame */uint32_t width;                /* 模组的当前分辨率及帧率 */uint32_t height;uint32_t fps;uint8_t bl;                    /*0:auto, 1:50Hz light, 2:60Hz light */uint8_taf;unsigned long flags;           /* flags for cam on/off, af on/off */unsigned long res_flags;       /* flags for resolution */unsigned long night_mode;struct clk *camera;            /* camera clk */};

struct cam_info 结构主要负责和 cam_core.c 交互，通过指针 priv 指向模组的私有操作接口struct cam_priv，该结构定义如下：

struct cam_priv {char     *name;        /* 模组名称 */uint16_t addr;         /* 模组i2c地址 */uint32_t i2c_bus;      /* 模组i2c总线号 */uint32_t subdev_id;    /* 前后camera标记 */uint32_t fmt_num;      /* 模组支持的格式数量 */uint32_t res_num;      /* 模组支持的分辨率数量 */uint32_t ctl_num;      /* 模组支持的特殊操作数量 */struct camera_fmt      *fmt_list;  /* 模组支持的格式列表 */struct camera_res      *res_list;  /* 模组支持的分辨率列表 */struct camera_control  *ctl_list;  /* 模组支持的特殊操作列表 */struct i2c_device_id   *id_table;  /* i2c id 列表 */int (*Open)(struct cam_info *info);  /* 打开模组 */int (*Close)(struct cam_info *info); /* 关闭模组 */int (*Set_Preview)(struct cam_info *info);   /* 预览操作接口 */int (*Set_Capture)(struct cam_info *info);   /* 拍照操作接口 */int (*Set_Config)(struct cam_info *info);    /* 配置操作接口 */int (*Set_Resolution)(struct cam_info *info, int val);  /* 分辨率操作接口 */int (*Request_Gpio)(void);  /* Gpio申请和释放 */int (*Free_Gpio)(void);int (*Detect_PowerON)(struct cam_info *info); /* 模组自动探测接口 */int (*Detect_PowerOFF)(struct cam_info *info);int (*Detect_ReadId)(struct cam_info *info);};

二、cam_core 主要接口解析

1、register 接口

模组注册到内核用 init_atxx_cam -> register_cam_device 接口，接口定义如下：

/* 主要完成camera模组的探测工作并将其注册到内核中 */static int register_cam_device(struct cam_info *info){int ret;struct i2c_adapter *adapter;struct i2c_board_info board_info;memset(&board_info, 0, sizeof(struct i2c_board_info));board_info.addr = info->priv->addr;strlcpy(board_info.type, info->priv->name, I2C_NAME_SIZE);/* 动态创建i2c从设备 */adapter = i2c_get_adapter(info->priv->i2c_bus);if (adapter == NULL) {cam_err("can't get i2c adapter %d\n", info->priv->i2c_bus);return -ENODEV;}info->i2c_dev = i2c_new_device(adapter, &board_info);i2c_put_adapter(adapter);if (info->i2c_dev == NULL) {cam_err("can't add i2c device at 0x%x\n", board_info.addr);return -ENODEV;}info->camera = clk_get(&info->i2c_dev->dev, "camera");if (IS_ERR(info->camera)) {cam_err("can't get camera clock\n");ret = -ENODEV;goto exit;}/* 申请Gpio并打开模组电源 */info->priv->Request_Gpio();info->priv->Detect_PowerON(info);/* 设置时钟 */clk_set_rate(info->camera, ATXX_CAM_CLOCK);clk_enable(info->camera);msleep(10);/* 读取模组id */ret = info->priv->Detect_ReadId(info);if(ret) {cam_err("can't detect this camera: %s\n", info->priv->name);goto exit_detect;}if(info->priv->subdev_id == ATXX_SUBDEV_FORE_CAM) {fore_cam_driver.id_table = info->priv->id_table;ret = i2c_add_driver(&fore_cam_driver);if(ret) {cam_err("can't add i2c driver\n");goto exit_detect;}} else {rear_cam_driver.id_table = info->priv->id_table;ret = i2c_add_driver(&rear_cam_driver);if(ret) {cam_err("can't add i2c driver\n");goto exit_detect;}}/* 初始化v4l2子设备 */v4l2_i2c_subdev_init(&info->sd, info->i2c_dev, &cam_ops);info->priv->Set_Config(info);/* 注册到内核 */ret = atxx_cam_register_sensor(&info->sd, info->priv->subdev_id);if(ret) {cam_err("can't register this camera: %s\n", info->priv->name);goto exit_detect;}clk_disable(info->camera);info->priv->Detect_PowerOFF(info);info->priv->Free_Gpio();info->flags = 0;return 0;exit_detect:clk_disable(info->camera);clk_put(info->camera);info->priv->Detect_PowerOFF(info);info->priv->Free_Gpio();exit:i2c_unregister_device(info->i2c_dev);return ret;}/* 初始化模组调用接口，参数为模组的cam_priv */int init_atxx_cam(struct cam_priv *priv){int ret;struct cam_info *info;info = kzalloc(sizeof(struct cam_info), GFP_KERNEL);if(info == NULL)return -ENOMEM;info->priv = priv;ret = register_cam_device(info);if(ret) {kfree(info);return ret;}return 0;}EXPORT_SYMBOL(init_atxx_cam);

2、v4l2 接口

在 cam_core 中主要完成 v4l2 子设备相关的操作，涉及到的数据结构和接口如下：

static const struct v4l2_subdev_core_ops cam_core_ops = {.g_ctrl    = cam_g_ctrl,    /* 获取当前命令值 */.s_ctrl    = cam_s_ctrl,    /* 发送命令值 */.queryctrl = cam_queryctrl, /* 查询模组是否支持该命令 */.reset     = cam_reset,     /* 复位模组 */.init      = cam_init,      /* 初始化模组 */.ioctl     = cam_ioctl,     /* 保留备用 */};static const struct v4l2_subdev_video_ops cam_video_ops = {.s_fmt    = cam_s_fmt,      /* 设置模组捕获视频的格式 */.try_fmt  = cam_try_fmt,    /* 尝试是否支持该格式 */.enum_fmt = cam_enum_fmt,   /* 枚举设备支持的格式 */};static const struct v4l2_subdev_ops cam_ops = {.core  = &cam_core_ops,     /* v4l2通用接口 */.video = &cam_video_ops,    /* v4l2视频接口 */};

3、i2c 通信接口

大部分 camera 寄存器的地址和值都是 8 位或者 16 位数据，因此可以将 i2c 通信接口简化，建立如下结构来描述寄存器地址和值：

/* 8 bit */struct cam_reg {unsigned char reg;   /* 8位寄存器地址 */unsigned char val;   /* 8位寄存器值 */};/* 16 bit */struct cam_reg {unsigned short reg;   /* 16位寄存器地址 */unsigned char val;    /* 8位寄存器值 */};

封装的 8 位通信接口如下：

uint8_t cam_read_byte(struct i2c_client *client, uint8_t reg_idx);int cam_write_byte(struct i2c_client *client, uint8_t reg_idx, uint8_t val);

在模组驱动中使用示例如下：

/*********************************************************************** * Camera Common Function                                              * ***********************************************************************/struct cam_reg {unsigned char reg;unsigned char val;};static int write_regs(struct cam_info *info, const struct cam_reg reglist[]){const struct cam_reg *next = reglist;while (!((next->reg == REG_TERM) && (next->val == VAL_TERM))){cam_write_byte(info->i2c_dev, next->reg, next->val);next++;}return 0;}/*********************************************************************** * Camera Initialize Function                                          * ***********************************************************************/static struct cam_reg cam_set_initialize[] = {{0xfc, 0x16},...{REG_TERM, VAL_TERM}};static struct cam_reg cam_set_preview[] = {{REG_TERM, VAL_TERM}};static struct cam_reg cam_set_capture[] = {{REG_TERM, VAL_TERM}};struct cam_reg* cam_reg_init[CAM_INIT_MAX] ={cam_set_initialize,cam_set_preview,cam_set_capture};static int cam_initialize(struct cam_info *info){return write_regs(info, cam_reg_init[CAM_INIT]);}static int cam_preview(struct cam_info *info){return write_regs(info, cam_reg_init[CAM_PREVIEW]);}static int cam_capture(struct cam_info *info){return write_regs(info, cam_reg_init[CAM_CAPTRUE]);}

三、camera 模组驱动接口解析
在模组驱动中主要工作是实现 struct cam_priv 中的接口，然后调用 init_atxx_cam 注册：

static struct cam_priv priv = {.name       = ATXX_CAM_NAME,.addr       = ATXX_CAM_ADDR,.i2c_bus    = ATXX_CAM_BUS,.subdev_id  = ATXX_CAM_SUBDEV,.fmt_num    = N_FORMATS,.res_num    = N_RESOLUTIONS,.ctl_num    = N_CONTROLS,.fmt_list   = cam_fmt_list,.res_list   = cam_res_list,.ctl_list   = cam_ctl_list,.id_table   = cam_id_table,.Open       = cam_open,.Close      = cam_close,.Set_Preview     = cam_preview,.Set_Capture     = cam_capture,.Set_Config      = cam_config,.Set_Resolution  = cam_resolution,.Request_Gpio    = cam_gpio_request,.Free_Gpio       = cam_gpio_free,.Detect_PowerON  = detect_poweron,.Detect_PowerOFF = detect_poweroff,.Detect_ReadId   = detect_readid,};static int __init cam_init(void){return init_atxx_cam(&priv);}

经过优化之后 camera 模组的代码耦合度很低，新增模组 driver 时只需要将别的模组 driver 拷贝一份然后修改一下宏定义和寄存器值就可以用了，而且每个模组 driver 的代码比之前少了500行左右，看起来也比较整洁，达到了预期目标。