前面在Exynos4412 IIC总线驱动开发（一）—— IIC 基础概念及驱动架构分析 中学习了IIC驱动的架构，下面进入我们的驱动开发过程          首先看一张代码层次图，有助于我们的理解


       上面这些代码的展示是告诉我们：linux内核和芯片提供商为我们的的驱动程序提供了 i2c驱动的框架，以及框架底层与硬件相关的代码的实现。 　  剩下的就是针对挂载在i2c两线上的i2c设备了device，而编写的即具体设备驱动了，这里的设备就是硬件接口外挂载的设备，而非硬件接口本身（soc硬件接口本身的驱动可以理解为总线驱动）

一、编写驱动需要完成的工作        编写具体的I2C驱动时，工程师需要处理的主要工作如下： 1)、提供I2C适配器的硬件驱动，探测，初始化I2C适配器(如申请I2C的I/O地址和中断号)，驱动CPU控制的I2C适配器从硬件上产生。 2)、提供I2C控制的algorithm, 用具体适配器的xxx_xfer()函数填充i2c_algorithm的master_xfer指针，并把i2c_algorithm指针赋给i2c_adapter的algo指针。 3)、实现I2C设备驱动中的i2c_driver接口，用具体yyy的yyy_probe()，yyy_remove()，yyy_suspend(),yyy_resume()函数指针和i2c_device_id设备ID表赋给i2c_driver的probe,remove,suspend,resume和id_table指针。 4)、实现I2C设备所对应类型的具体驱动，i2c_driver只是实现设备与总线的挂接。 　　上面的工作中前两个属于I2C总线驱动，后面两个属于I2C设备驱动。
二、开发实例 ------------------------------------------------------------------- 开发板：Exynos4412-fs4412 Linux 内核版本：Linux 3.14 IIC 从机对象：陀螺仪MPU6050 -------------------------------------------------------------------- 1、查看原理图 对应核心板pin

从机地址


可以获取的信息： 1、MPU6050 对应 IIC 通道5； 2、对应中断 EINT27  父节点 GPX3  3 3、因为ad0接地，所以从设备地址0x68       base address 0x138B0000

2、创建设备树节点       通过上面获取的信息，可以写出 i2c@138b0000 { #address-cells = <1>; #size-cells = <0>; samsung,i2c-sda-delay = <100>; samsung,i2c-max-bus-freq = <20000>; pinctrl-0 = <&i2c5_bus>; pinctrl-names = "default"; status = "okay"; pmu6050-3-asix@68 { compatible = "invense,mpu6050"; reg = <0x68>; interrupt-parent = <&gpx3>; interrupts = <3 2>; }; };
3、MPU6050相应寄存器 #define SMPLRT_DIV 0x19 //采样率分频，典型值： 0x07(125Hz) */ #define CONFIG 0x1A // 低通滤波频率，典型值： 0x06(5Hz) */ #define GYRO_CONFIG 0x1B // 陀螺仪自检及测量范围，典型值： 0x18(不自检，2000deg/s) */ #define ACCEL_CONFIG 0x1C // 加速计自检、测量范围及高通滤波频率，典型值： 0x01(不自检， 2G， 5Hz) */ #define ACCEL_XOUT_H 0x3B // 存储最近的 X 轴、 Y 轴、 Z 轴加速度感应器的测量值 */ #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 // 存储的最近温度传感器的测量值 */ #define TEMP_OUT_L 0x42 #define GYRO_XOUT_H 0x43 // 存储最近的 X 轴、 Y 轴、 Z 轴陀螺仪感应器的测量值 */ #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 // 电源管理，典型值： 0x00(正常启用) */ #define WHO_AM_I 0x75 //IIC 地址寄存器(默认数值 0x68，只读) */
4、具体程序 mpu6050.h#ifndef MPU6050_HHHH #define MPU6050_HHHH #define MPU6050_MAGIC 'K' union mpu6050_data { struct { unsigned short x; unsigned short y; unsigned short z; }accel; struct { unsigned short x; unsigned short y; unsigned short z; }gyro; unsigned short temp; }; #define GET_ACCEL _IOR(MPU6050_MAGIC, 0, union mpu6050_data) #define GET_GYRO _IOR(MPU6050_MAGIC, 1, union mpu6050_data) #define GET_TEMP _IOR(MPU6050_MAGIC, 2, union mpu6050_data) #endif i2c_driver #include #include #include #include #include #include #include #include #include "mpu6050.h" MODULE_LICENSE("GPL"); #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 #define MPU6050_MAJOR 500 #define MPU6050_MINOR 0 struct mpu6050_device { struct cdev cdev; struct i2c_client *client; }; struct mpu6050_device *mpu6050; static int mpu6050_read_byte(struct i2c_client *client, unsigned char reg) { int ret; char txbuf[1] = { reg }; char rxbuf[1]; struct i2c_msg msg[2] = { {client->addr, 0, 1, txbuf}, {client->addr, I2C_M_RD, 1, rxbuf} }; ret = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg)); if (ret < 0) { printk("ret = %d ", ret); return ret; } return rxbuf[0]; } static int mpu6050_write_byte(struct i2c_client *client, unsigned char reg, unsigned char val) { char txbuf[2] = {reg, val}; struct i2c_msg msg[2] = { {client->addr, 0, 2, txbuf}, }; i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg)); return 0; } static int mpu6050_open(struct inode *inode, struct file *file) { return 0; } static int mpu6050_release(struct inode *inode, struct file *file) { return 0; } static long mpu6050_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { union mpu6050_data data; struct i2c_client *client = mpu6050->client; switch(cmd) { case GET_ACCEL: data.accel.x = mpu6050_read_byte(client, ACCEL_XOUT_L); data.accel.x |= mpu6050_read_byte(client, ACCEL_XOUT_H) << 8; data.accel.y = mpu6050_read_byte(client, ACCEL_YOUT_L); data.accel.y |= mpu6050_read_byte(client, ACCEL_YOUT_H) << 8; data.accel.z = mpu6050_read_byte(client, ACCEL_ZOUT_L); data.accel.z |= mpu6050_read_byte(client, ACCEL_ZOUT_H) << 8; break; case GET_GYRO: data.gyro.x = mpu6050_read_byte(client, GYRO_XOUT_L); data.gyro.x |= mpu6050_read_byte(client, GYRO_XOUT_H) << 8; data.gyro.y = mpu6050_read_byte(client, GYRO_YOUT_L); data.gyro.y |= mpu6050_read_byte(client, GYRO_YOUT_H) << 8; data.gyro.z = mpu6050_read_byte(client, GYRO_ZOUT_L); data.gyro.z |= mpu6050_read_byte(client, GYRO_ZOUT_H) << 8; break; case GET_TEMP: data.temp = mpu6050_read_byte(client, TEMP_OUT_L); data.temp |= mpu6050_read_byte(client, TEMP_OUT_H) << 8; break; default: printk("invalid argument "); return -EINVAL; } if (copy_to_user((void *)arg, &data, sizeof(data))) return -EFAULT; return sizeof(data); } struct file_operations mpu6050_fops = { .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 devno = MKDEV(MPU6050_MAJOR, MPU6050_MINOR); printk("match OK! "); mpu6050 = kzalloc(sizeof(*mpu6050), GFP_KERNEL); if (mpu6050 == NULL) { return -ENOMEM; } mpu6050->client = client; ret = register_chrdev_region(devno, 1, "mpu6050"); if (ret < 0) { printk("failed to register char device region! "); goto err1; } cdev_init(&mpu6050->cdev, &mpu6050_fops); mpu6050->cdev.owner = THIS_MODULE; ret = cdev_add(&mpu6050->cdev, devno, 1); if (ret < 0) { printk("failed to add device "); goto err2; } mpu6050_write_byte(client, PWR_MGMT_1, 0x00); mpu6050_write_byte(client, SMPLRT_DIV, 0x07); mpu6050_write_byte(client, CONFIG, 0x06); mpu6050_write_byte(client, GYRO_CONFIG, 0xF8); mpu6050_write_byte(client, ACCEL_CONFIG, 0x19); return 0; err2: unregister_chrdev_region(devno, 1); err1: kfree(mpu6050); return ret; } static int mpu6050_remove(struct i2c_client *client) { dev_t devno = MKDEV(MPU6050_MAJOR, MPU6050_MINOR); cdev_del(&mpu6050->cdev); unregister_chrdev_region(devno, 1); kfree(mpu6050); return 0; } static const struct i2c_device_id mpu6050_id[] = { { "mpu6050", 0}, {} }; static struct of_device_id mpu6050_dt_match[] = { {.compatible = "invense,mpu6050" }, {/*northing to be done*/}, }; struct i2c_driver mpu6050_driver = { .driver = { .name = "mpu6050", .owner = THIS_MODULE, .of_match_table = of_match_ptr(mpu6050_dt_match), }, .probe = mpu6050_probe, .remove = mpu6050_remove, .id_table = mpu6050_id, }; static init _init mpu6050_init(void) { return i2c_add_driver(&mpu6050_driver); } static void _exit mpu6050_exit(void) { return i2c_del_driver(&mpu6050_driver); } module_init(&mpu6050_init); module_exit(&mpu6050_exit);
test.c#include #include #include #include #include #include "mpu6050.h" int main(int argc, const char *argv[]) { int fd; union mpu6050_data data; fd = open("/dev/mpu6050", O_RDWR); if (fd < 0) { perror("open"); exit(1); } while(1) { ioctl(fd, GET_ACCEL, &data); printf("acceleration data: x = %04x, y = %04x, z = %04x ", data.accel.x, data.accel.y, data.accel.z); ioctl(fd, GET_GYRO, &data); printf("gyroscope data: x = %04x, y = %04x, z = %04x ", data.accel.x, data.accel.y, data.accel.z); sleep(1); } close(fd); return 0; }