x4412 i2c设备驱动开发实例(mpu6050)

        MPU6050 包括陀螺仪和加速度传感器功能,陀螺仪和加速度传感器分别用三个 16bit 的数据表示,量程和精度都是可编程的,可按需求设置,具体 MPU6050 参数参照芯片手册。Exynos4412 共有八组 I2C 控制器,我们使用x4412引出的i2c6连接MPU6050，如下图所示。

首先需要修改设备树，添加I2C6节点，如下

i2c@138C0000 {
		samsung,i2c-sda-delay = <100>;
		samsung,i2c-max-bus-freq = <20000>;
		pinctrl-0 = <&i2c6_bus>;
		pinctrl-names = "default";
		status = "okay";

		mpu6050-3-axis@68 {
			compatible = "invensense,mpu6050";
			reg = <0x68>;
			interrupt-parent = <&gpx3>;
			interrupts = <3 2>;
		};
};

接下来开发对应的驱动程序，配置初始化mpu6050。配置代码如下

#include 
#include 
#include 

#include 
#include 

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include "mpu6050.h"

#define FSRTC_MAJOR	256
#define FSRTC_MINOR	9
#define FSRTC_DEV_NAME	"mpu6050"

#define SMPLRT_DIV	0x19
#define CONFIG		0x1A
#define GYRO_CONFIG	0x1B
#define ACCEL_CONFIG	0x1C
#define ACCEL_XOUT_H	0x3B
#define ACCEL_XOUT_L	0x3C
#define ACCEL_YOUT_H	0x3D
#define ACCEL_YOUT_L	0x3E
#define ACCEL_ZOUT_H	0x3F
#define ACCEL_ZOUT_L	0x40
#define TEMP_OUT_H	0x41
#define TEMP_OUT_L	0x42
#define GYRO_XOUT_H	0x43
#define GYRO_XOUT_L	0x44
#define GYRO_YOUT_H	0x45
#define GYRO_YOUT_L	0x46
#define GYRO_ZOUT_H	0x47
#define GYRO_ZOUT_L	0x48
#define PWR_MGMT_1	0x6B

struct mpu6050_dev {
	struct i2c_client *client;
	atomic_t available;
	struct cdev cdev;
	struct device *device;
};
static struct class *mpu6050_cls;

static int mpu6050_open(struct inode *inode, struct file *filp)
{
	struct mpu6050_dev *mpu6050 = container_of(inode->i_cdev, struct mpu6050_dev, cdev);

	filp->private_data = mpu6050;
	if (atomic_dec_and_test(&mpu6050->available))//dec1 and check is it zero,if it is zero,return true
		return 0;
	else {
		atomic_inc(&mpu6050->available);//inc ,
		return -EBUSY;
	}
}

static int mpu6050_release(struct inode *inode, struct file *filp)
{
	struct mpu6050_dev *mpu6050 = filp->private_data;

	atomic_inc(&mpu6050->available);
	return 0;
}

static long mpu6050_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
	struct mpu6050_dev *mpu6050 = filp->private_data;
	struct atg_val val;

	if (_IOC_TYPE(cmd) != MPU6050_MAGIC)
		return -ENOTTY;

	switch (cmd) {
	case MPU6050_GET_VAL:
		val.accelx = i2c_smbus_read_word_data(mpu6050->client, ACCEL_XOUT_H);//read
		val.accely = i2c_smbus_read_word_data(mpu6050->client, ACCEL_YOUT_H);
		val.accelz = i2c_smbus_read_word_data(mpu6050->client, ACCEL_ZOUT_H);
		val.temp   = i2c_smbus_read_word_data(mpu6050->client, TEMP_OUT_H);
		val.gyrox  = i2c_smbus_read_word_data(mpu6050->client, GYRO_XOUT_H);
		val.gyroy  = i2c_smbus_read_word_data(mpu6050->client, GYRO_YOUT_H);
		val.gyroz  = i2c_smbus_read_word_data(mpu6050->client, GYRO_ZOUT_H);
		val.accelx = be16_to_cpu(val.accelx);//转换成大段格式
		val.accely = be16_to_cpu(val.accely);
		val.accelz = be16_to_cpu(val.accelz);
		val.temp   = be16_to_cpu(val.temp);
		val.gyrox  = be16_to_cpu(val.gyrox);
		val.gyroy  = be16_to_cpu(val.gyroy);
		val.gyroz  = be16_to_cpu(val.gyroz);
		if (copy_to_user((struct atg_val __user *)arg, &val, sizeof(struct atg_val)))
			return -EFAULT;
		break;
	default:
		return -ENOTTY;
	}

	return 0;
}

static struct file_operations mpu6050_ops = {
	.owner = THIS_MODULE,
	.open = mpu6050_open,
	.release = mpu6050_release,
	.unlocked_ioctl = mpu6050_ioctl,
};

static int mpu6050_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
	int ret;
	dev_t dev;
	struct mpu6050_dev *mpu6050;

	dev = MKDEV(FSRTC_MAJOR, FSRTC_MINOR);
	ret = register_chrdev_region(dev, 1, FSRTC_DEV_NAME);
	if (ret)
		goto reg_err;

	
	mpu6050_cls = class_create(THIS_MODULE,"mpu6050");
	if(IS_ERR(mpu6050_cls)){
		ret = PTR_ERR(mpu6050_cls);
		goto mem_err;
	}


	mpu6050 = kzalloc(sizeof(struct mpu6050_dev), GFP_KERNEL);
	if (!mpu6050) {
		ret = -ENOMEM;
		goto cls_err;
	}

	mpu6050->device = device_create(mpu6050_cls, NULL, dev, NULL, "mpu6050");
	if (IS_ERR(mpu6050->device)) {
        	ret = PTR_ERR(mpu6050->device);
        	goto add_err;
    	}

	i2c_set_clientdata(client, mpu6050);
	mpu6050->client = client;

	cdev_init(&mpu6050->cdev, &mpu6050_ops);
	mpu6050->cdev.owner = THIS_MODULE;
	ret = cdev_add(&mpu6050->cdev, dev, 1);
	if (ret)
		goto add_err;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA)) {
		ret = -ENOSYS;
		goto fun_err;
	}

	i2c_smbus_write_byte_data(client, PWR_MGMT_1, 0x80);
	msleep(200);
	i2c_smbus_write_byte_data(client, PWR_MGMT_1, 0x40);
	i2c_smbus_write_byte_data(client, PWR_MGMT_1, 0x00);

	i2c_smbus_write_byte_data(client, SMPLRT_DIV,   0x7);
	i2c_smbus_write_byte_data(client, CONFIG,       0x6);
	i2c_smbus_write_byte_data(client, GYRO_CONFIG,  0x3 << 3); 
	i2c_smbus_write_byte_data(client, ACCEL_CONFIG, 0x3 << 3);

	atomic_set(&mpu6050->available, 1);

	return 0;

fun_err:
	cdev_del(&mpu6050->cdev);
add_err:
	kfree(mpu6050);
cls_err:
	class_destroy(mpu6050_cls);
mem_err:
	unregister_chrdev_region(dev, 1);
reg_err:
	printk("erro\n");
	return ret;
}

static int mpu6050_remove(struct i2c_client *client)
{
	dev_t dev;
	struct mpu6050_dev *mpu6050 = i2c_get_clientdata(client);

	dev = MKDEV(FSRTC_MAJOR, FSRTC_MINOR);

	cdev_del(&mpu6050->cdev);
	kfree(mpu6050);
	unregister_chrdev_region(dev, 1);
	device_unregister(mpu6050->device);
	class_destroy(mpu6050_cls);
	return 0;
}

static const struct i2c_device_id mpu6050_id[] = {
	{"mpu6050", 0},
	{}
};

MODULE_DEVICE_TABLE(i2c, mpu6050_id);

static struct i2c_driver mpu6050_driver = {
	.probe          =       mpu6050_probe,
	.remove         =       mpu6050_remove,
	.id_table       =       mpu6050_id,
	.driver = {
		.owner  =       THIS_MODULE,
		.name   =       "mpu6050",
	},
};

module_i2c_driver(mpu6050_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Kevin Jiang ");
MODULE_DESCRIPTION("MPU6050 driver");

然后重新编译dtb并生成设备驱动文件，替换原本的dtb并加载驱动程序。由于上述程序使用了自动创建设备节点的class_create,所以不再需要手动到/dev添加设备节点，驱动程序加载成功后会自动生成mpu6050设备文件。我们通过读写该文件就可以使用mpu6050。

        接下来我们需要添加测试驱动文件，检查驱动是否正常工作。测试源码如下：

#include 
#include 
#include 
#include 
#include 

struct atg_val {
	short accelx;
	short accely;
	short accelz;
	short temp;
	short gyrox;
	short gyroy;
	short gyroz;
};

#define MPU6050_MAGIC	'm'

#define MPU6050_GET_VAL	_IOR(MPU6050_MAGIC, 0, struct atg_val)


int main(int argc, char *argv[])
{
	int fd;
	struct atg_val val;


	fd = open("/dev/mpu6050", O_RDWR);

	while (2) {
		ioctl(fd, MPU6050_GET_VAL, &val);

		printf("accelx: %.2f\n", val.accelx / 2048.0);
		printf("accely: %.2f\n", val.accely / 2048.0);
		printf("accelz: %.2f\n", val.accelz / 2048.0);
		printf("temp: %.2f\n", val.temp / 340.0 + 36.53); 
		printf("gyrox: %.2f\n", val.gyrox / 16.4);
		printf("gyroy: %.2f\n", val.gyroy / 16.4);
		printf("gyroz: %.2f\n", val.gyroz / 16.4);


		sleep(1);
	}
}

利用arm-linux-gcc编译生成测试程序，在x4412上运行，如果可以在终端上动态显示相关信息，可知该驱动工作正常