上一節介紹了I2C的相關協議,本節主要講I2C的設備驅動的創建
在內核iTop4412_Kernel_3.0\Documentation\i2c\instantiating-devices這個文檔介紹了4種創建I2C設備的方法
1設備的4種構建方法
1.1定義一個i2c_board_info,裏面有名字,地址
然後i2c_register_board_info(busnum,……)(把他們放入鏈表)
list_add_tail(&devinfo->list, &__i2c_board_list);
鏈表何時使用
i2c_register_adapter->i2c_scan_static_board_info(struct i2c_adapter *adapter)>i2c_new_device
使用限制:必須i2c_register_adapter之前i2c_register_board_info
所以不適合我們動態加載insmod
1.2直接i2c_new_device,i2c_new_probe_device
1.2.1 i2c_new_device :認爲設備肯定存在
1.2.2 i2c_new_probed_device :對於“已經識別出來的設備”probed__device”,纔會(new)
probe(adap, addr_list[i] //確定設備是否真的存在
info->addr = addr_list[i];
return i2c_new_device(adap, info);
1.3從用戶空間創建設備
創建設備
echo at24c02 0x50 > /sys/class/i2c-adapter/i2c-7/new_device
刪除設備
echo 0x50 > /sys/class/i2c-adapter/i2c-7/new_device
導致i2c_unregister_device
1.4前面的3種方法都要確定適配器(I2C總線、I2C控制器)
如果事先不知道這個I2C設備在哪個適配器,怎麼辦?去class表示的所有的適配器上查找,有一些I2C設備的地址是一樣的,怎麼繼續分配它是哪一款?用detect函數確定
static struct i2c_driver at24cxx_driver = {
.class=I2C_CLASS_HWMON//哪一類設備器查找支持的設備
.driver = {
.name = "100ask",
},
.probe = at24cxx_probe,
.remove = __devexit_p(at24cxx_remove),
.id_table = at24cxx_id_table,
.detect=at24cxx_detect,//用這個函數來檢測能否找到設備
.address_list=addr_list,//這些設備的地址
};
去“class表示的這一類“i2c適配器,用“detect函數“來確定能否找到"address_list"裏的設備
如果能找到就調用好i2c_new_device來註冊i2c_client,這會和i2c_driver的id_table比較,如果匹配,調用probe
首先在入口函數中調用.i2c_add_driver
a.i2c_add_driver
i2c_register_driver.
at24cxx_driver放入i2c_bus_type的drv鏈表,
並且從dev鏈表裏取出能匹配的i2c_client並調用probe
driver_register
如果dev鏈表沒有,此時則調用i2c_for_each_dev(driver,__process_new_driver); 對每一個適配器進行循環
b.對於每一個是適配器,調用__process_new_driver
對於每一個適配器,調用它的函數確定address_list裏的設備是否存在
如果存在,在調用detect進一步確定、設置,然後i2c_new_device
i2c_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);
//判斷
if(!i2c_default_probe(adapter,addr))
return 0;
memset(&info,0,sizeof(struct i2c_board_info));
info.addr=addr;
//設置info的結構體
err=driver->detect(temp_client,&info);
2.實例驅動程序編寫
/*
I2C設備:mpu6050
內核版本:3.0.15
開發板: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 <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/err.h>
#include "mpu6050.h"
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <asm/uaccess.h>
#include <linux/delay.h>
#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);//採樣頻率分頻器
mpu6050_write_byte(my_client,CONFIG,0x06);//配置EXT_SYNC_SET和FSYNC,初始化溫度
mpu6050_write_byte(my_client,GYRO_CONFIG,0xF8);//選通陀螺儀的三軸及量程
mpu6050_write_byte(my_client,ACCEL_CONFIG,0x19);//執行加速度自檢和量程
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);//必須先註銷驅動
i2c_unregister_device(mpu6050_client);
}
module_init(mpu6050_init);
module_exit(mpu6050_exit);
MODULE_LICENSE("GPL");
測試程序:
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/ioctl.h>
#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;
}
測試程序編譯
arm-none-Linux-gnueabi-gcc mpu6050_app.c -o mpu6050_app -static
下載到開發板中
insmod mpu6050.ko
./mpu6050_app
acceleration data: x = 0183,y = 001a,z = f814
gyroscope data : x = 07ea,y = 0932,z = 0c0e