linux摄像头I2C驱动初始化

阅读linux的ov2655的驱动程序时，并没有发现I2C设备驱动的初始化函数i2c_add_driver，
只是定义了
static struct v4l2_i2c_driver_data v4l2_i2c_data =
{
    .name = S5K4BA_DRIVER_NAME,
    .probe = ov2655_probe,
    .remove = __devexit_p(ov2655_remove),
    .id_table = ov2655_id,
};

其实相关I2C初始化函数在v4l2-i2c-drv.h里
I2C摄像头驱动程序都会包含该文件
#include

该文件代码很简单，I2C驱动初始化如下：
static int __init v4l2_i2c_drv_init(void)
{
    //其中的v4l2_i2c_data就是前面提到的在ov2655驱动里定义结构体。
    v4l2_i2c_driver.driver.name = v4l2_i2c_data.name;
    v4l2_i2c_driver.command = v4l2_i2c_data.command;
    v4l2_i2c_driver.probe = v4l2_i2c_data.probe;
    v4l2_i2c_driver.remove = v4l2_i2c_data.remove;
    v4l2_i2c_driver.suspend = v4l2_i2c_data.suspend;
    v4l2_i2c_driver.resume = v4l2_i2c_data.resume;
    v4l2_i2c_driver.id_table = v4l2_i2c_data.id_table;
    return i2c_add_driver(&v4l2_i2c_driver);
}


static void __exit v4l2_i2c_drv_cleanup(void)
{
    i2c_del_driver(&v4l2_i2c_driver);
}

module_init(v4l2_i2c_drv_init);
module_exit(v4l2_i2c_drv_cleanup);


之后调用v4l2_i2c_driver.probe，也就是v4l2_i2c_data.probe，即ov2655_probe。

注册子设备
v4l2_i2c_subdev_init(sd, client, &ov2655_ops);

ov2655_ops包含了操作接口函数的结构体
static const struct v4l2_subdev_core_ops ov2655_core_ops =
{
    .init = ov2655_init, /* initializing API */
    .s_config = ov2655_s_config, /* Fetch platform data */
    .queryctrl = ov2655_queryctrl,
    .querymenu = ov2655_querymenu,
    .g_ctrl = ov2655_g_ctrl,
    .s_ctrl = ov2655_s_ctrl,
};

static const struct v4l2_subdev_video_ops ov2655_video_ops =
{
    .g_fmt = ov2655_g_fmt,
    .s_fmt = ov2655_s_fmt,
    .enum_framesizes = ov2655_enum_framesizes,
    .enum_frameintervals = ov2655_enum_frameintervals,
    .enum_fmt = ov2655_enum_fmt,
    .try_fmt = ov2655_try_fmt,
    .g_parm = ov2655_g_parm,
    .s_parm = ov2655_s_parm,
};

static const struct v4l2_subdev_ops ov2655_ops =
{
    .core = &ov2655_core_ops,
    .video = &ov2655_video_ops,
};

最后调用ov2655_init完成摄像头初始化。