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上一节介绍了I2C的相关协议，本节主要讲I2C的设备驱动的创建
在内核iTop4412_Kernel_3.0\Documentation\i2c\instantiating-devices这个文档介绍了4种创建I2C设备的方法 1设备的4种构建方法 1.1定义一个i2c_board_info,里面有名字，地址 然后i2c_register_board_info(busnum,……)(把他们放入链表) list_add_tail(&devinfo->list, &__i2c_board_list); 链表何时使用 i2c_register_adapter->i2c_scan_static_board_info(struct i2c_adapter *adapter)>i2c_new_device使用限制：必须i2c_register_adapter之前i2c_register_board_info
所以不适合我们动态加载insmod 1.2直接i2c_new_device,i2c_new_probe_device 1.2.1 i2c_new_device :认为设备肯定存在 1.2.2 i2c_new_probed_device :对于“已经识别出来的设备”probed__device”,才会（new） probe(adap, addr_list[i] //确定设备是否真的存在 info->addr = addr_list[i]; return i2c_new_device(adap, info); 1.3从用户空间创建设备 创建设备 echo at24c02 0x50 > /sys/class/i2c-adapter/i2c-7/new_device 删除设备 echo 0x50 > /sys/class/i2c-adapter/i2c-7/new_device 导致i2c_unregister_device 1.4前面的3种方法都要确定适配器（I2C总线、I2C控制器） 如果事先不知道这个I2C设备在哪个适配器，怎么办？去class表示的所有的适配器上查找，有一些I2C设备的地址是一样的，怎么继续分配它是哪一款？用detect函数确定static struct i2c_driver at24cxx_driver = { .class=I2C_CLASS_HWMON//哪一类设备器查找支持的设备 .driver = { .name = "100ask", }, .probe = at24cxx_probe, .remove = __devexit_p(at24cxx_remove), .id_table = at24cxx_id_table, .detect=at24cxx_detect,//用这个函数来检测能否找到设备 .address_list=addr_list,//这些设备的地址};去“class表示的这一类“i2c适配器，用“detect函数“来确定能否找到"address_list"里的设备如果能找到就调用好i2c_new_device来注册i2c_client,这会和i2c_driver的id_table比较，如果匹配，调用probe首先在入口函数中调用.i2c_add_drivera.i2c_add_driver i2c_register_driver. at24cxx_driver放入i2c_bus_type的drv链表, 并且从dev链表里取出能匹配的i2c_client并调用probe driver_register 如果dev链表没有，此时则调用i2c_for_each_dev(driver,__process_new_driver); 对每一个适配器进行循环b.对于每一个是适配器，调用__process_new_driver对于每一个适配器，调用它的函数确定address_list里的设备是否存在如果存在，在调用detect进一步确定、设置，然后i2c_new_devicei2c_for_each_dev(driver,__process_new_driver); __process_new_driver i2c_do_add_adapter i2c_detect(adap,driver); for(i=0;address_list[i]!=I2C_CLIENT_END;i+=1) err=i2c_detect_address(temp_client,driver); //判断 if(!i2c_default_probe(adapter,addr)) return 0; memset(&info,0,sizeof(struct i2c_board_info)); info.addr=addr; //设置info的结构体 err=driver->detect(temp_client,&info); 2.实例驱动程序编写
/*I2C设备：mpu6050内核版本：3.0.15开发板：itop4412*/
mpu6050.h
#ifndef __MPU6050_H_#define __MPU6050_H_#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 MPU6050.c
#include#include #include #include #include #include #include #include "mpu6050.h"#include #include #include #include #include #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 static int major;struct cdev cdev;static struct class *class;static const unsigned short addr_list[] = { 0x68,I2C_CLIENT_END};static struct i2c_client *mpu6050_client;static struct i2c_client *my_client;static int mpu6050_write_byte(struct i2c_client *client,unsigned char reg,unsigned char val){ if(!i2c_smbus_write_byte_data(client,reg,val)) return 2; else return -EIO; return 0;}static int mpu6050_read_byte(struct i2c_client *client,unsigned char reg){ unsigned char data; data=i2c_smbus_read_byte_data(client,reg); return data;}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 int mpu6050_ioctl(struct file *file, unsigned int cmd, unsigned long arg){ union mpu6050_data data; struct i2c_client *client = my_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; printk(KERN_EMERG"GET_ACCEL X = %04x\n",data.accel.x); printk(KERN_EMERG"GET_ACCEL y = %04x\n",data.accel.y); printk(KERN_EMERG"GET_ACCEL z = %04x\n",data.accel.z); printk("GET_ACCEL finished\n"); 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; printk("GET_GYRO finished\n"); 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("magic error\n"); return -EINVAL; } } if(copy_to_user((void*)arg,&data,sizeof(data))) return -EINVAL; return sizeof(data);}struct file_operations mpu6050_ops={ .owner = THIS_MODULE, .open = mpu6050_open, .release = mpu6050_release, .unlocked_ioctl = mpu6050_ioctl,};static int __devinit mpu6050_probe(struct i2c_client *client,const struct i2c_device_id *id){ printk("match\n"); my_client=kzalloc(sizeof(struct i2c_client),GFP_KERNEL); if(my_client == NULL) { return -ENOMEM; } my_client=client; major = register_chrdev(0, "mpu6050", &mpu6050_ops); class = class_create(THIS_MODULE, "mpu6050"); device_create(class, NULL, MKDEV(major, 0), NULL, "mpu6050"); printk("create successful\n"); /*mpu6050的初始化*/ mpu6050_write_byte(my_client,PWR_MGMT_1,0x00);//解除睡眠 mpu6050_write_byte(my_client,SMPLRT_DIV,0x07);//采样频率分频器 mpu6050_write_byte(my_client,CONFIG,0x06);//配置EXT_SYNC_SET和FSYNC，初始化温度 mpu6050_write_byte(my_client,GYRO_CONFIG,0xF8);//选通陀螺仪的三轴及量程 mpu6050_write_byte(my_client,ACCEL_CONFIG,0x19);//执行加速度自检和量程 printk("init finished\n"); return 0;}static int __devexit mpu6050_remove(struct i2c_client *client){ device_destroy(class,MKDEV(major, 0)); class_destroy(class); unregister_chrdev(major, "mpu6050"); return 0;}static const struct i2c_device_id mpu6050_id_table[] = { { "mpu6050", 0 }, { }};static struct i2c_driver mpu6050_driver = { .driver = { .name = "100ask", }, .probe = mpu6050_probe, .remove = __devexit_p(mpu6050_remove), .id_table = mpu6050_id_table,};static int mpu6050_init(void){ i2c_add_driver(&mpu6050_driver); struct i2c_adapter *i2c_adap; struct i2c_board_info mpu6050_info; memset(&mpu6050_info,0,sizeof(struct i2c_board_info)); strlcpy(mpu6050_info.type,"mpu6050",I2C_NAME_SIZE); i2c_adap=i2c_get_adapter(7); mpu6050_client=i2c_new_probed_device(i2c_adap,&mpu6050_info,addr_list,NULL); i2c_put_adapter(i2c_adap); if(mpu6050_client) return 0; else return -ENODEV; return 0;}static void mpu6050_exit(void){ i2c_del_driver(&mpu6050_driver);//必须先注销驱动 i2c_unregister_device(mpu6050_client);}module_init(mpu6050_init);module_exit(mpu6050_exit);MODULE_LICENSE("GPL");
测试程序：
#include#include #include #include #include #include"mpu6050.h"int main(int argc,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\n",data.accel.x,data.accel.y,data.accel.z); ioctl(fd,GET_GYRO,&data); printf("gyroscope data : x = %04x,y = %04x,z = %04x\n",data.gyro.x,data.gyro.y,data.gyro.z); sleep(1); } close(fd); return 0;}
测试程序编译
arm-none-Linux-gnueabi-gcc mpu6050_app.c -o mpu6050_app -static 下载到开发板中 insmod mpu6050.ko ./mpu6050_app acceleration data: x = 0183,y = 001a,z = f814 gyroscope data : x = 07ea,y = 0932,z = 0c0e转载地址：http://ixomb.baihongyu.com/