LINUX下I2C框架.doc

基于2440板子，linux内核下的I2C，操作E2PROM分析篇:AT24C02 LINUX I2C架构分析：简化：设备驱动层：提供策略（我们90%的任务）。（E2PROM驱动 /触摸屏驱动 /传感器驱动）总线驱动层：提供一个硬件操作能力。I2C控制驱动（总线驱动）在芯片（S3C2410）生产出来的时候生产厂商就已经写好了，且永远不变（1类芯片对应1种控制器驱动，控制器驱动就是去操作各种寄存器的值,实现标准I2C时序）I2C核心层：的作用在这就体现出来了，得用它来承上启下，连接设备驱动和总线驱动。open 最主要就是第5步（前面绕来绕去的不用管），1，打开open时，将获取到的adap （2440就一个）放到临时变量client结构中；2，将client挂到到file-private_data中。供以后读写使用。这样适配器adap就和file建立了某种联系。第二步的三个结构体都是临时变量。I2c_transfer() :只负责将Msg 给 adap。这个函数非常通用。不管读写，最终都会调用使用篇:每一个read, write 都会构建一个msg结构体（已包含从器件地址）并自动地先发送从器件地址，再发送后面的段内地址和数据。注意：赋值的地址应该右移1位因为底层处理的时候，会将传下去的数据左移1位取其最低7位。所以实际器件地址是0xa0 (1010 0000)，应用程序中应该是0x50 (0101 0000),当从控制I2C到另一个器件时，需要改的是从机地址（当然，也有片内地址）当增加适配器时，还需注意器件时挂在哪个适配器上。去掉此项为去掉通用接口,需自己写I2C驱动.此项为控制器驱动.附件/*利用通用驱动程序，在应用层使用 I2C*/#include#include#include#include#include#define I2C_SLAVE 0X0703int main (int argc,char *argv)/1,open device file int fd; int adapter_nr = 0; /* probably dynamically determined */ char filename20; char buf10;char rbuf10;unsigned char addr_data = 0x00; snprintf(filename, 19, /dev/i2c-%d, adapter_nr); fd = open(filename, O_RDWR); if (file 0) printf(open device file fail!n); return -1;/2,set slave addrint addr = 0x50; /* The I2C address ,0xa0 wrong, should be 0x50*/ ioctl(fd, I2C_SLAVE, addr);/3,send slave addr, register_addr(addr_data) and data buf0 = addr_data; buf1 = 0x92;/datawrite(fd, buf, 2);/*the write cmd will build a struct msg which contain the slave_addr, and send slave_addr first.*/4,read addr/4.1 send register addrwrite(fd,&addr_data,1);/4.2 read dataread(fd,&rbuf,1);printf(rbuf0 = 0x%xn,rbuf0);E2PROM驱动:(有误,可以参考大概思路)/*参照i2c-dev.c通用接口驱动，ds1682.c*/*参照i2c-dev.c通用接口驱动，ds1682.c*/#include#include#include#include#include#include#includeunsigned int gec_e2prom_major =0;struct class *gec_dev_class =NULL;/*不必深究，注意改动从器件地址0x50和 gec_e2prom_address_data*/static unsigned short ignore=I2C_CLIENT_END;static unsigned short normal_addr=0x50,I2C_CLIENT_END;static struct i2c_client_address_data gec_e2prom_address_data=.normal_i2c = normal_addr,.probe = ignore,.ignore = ignore,;/*不必深究，注意改动从器件地址0x50和 gec_e2prom_address_data*/struct i2c_client *gec_e2prom_client;static char wbut10;static char rbut10;static int gec_i2cdev_attach_adapter(struct i2c_adapter *adap)static int gec_i2cdev_attach_adapter(struct i2c_adapter *adap)static ssize_t gec_i2cdev_write(struct file *file, const char _user *buf, size_t count, loff_t *opps)/*1,构建1个消息结构体*/struct i2c_msg e2prom_msg1;/*2,设置片内地址*/wbut0 = 0x0;/*3要发的数据*/copy_from_user(&wbut1,buf,count);/*设置此结构体*/e2prom_mes0.addr = gec_e2prom_client-addr;e2prom_mes0.flags = 0;e2prom_mes0.len = count +1; /+1是加上片内地址e2prom_mes0.buf = wbut;/*发送数据到底层*/i2c_transfer(gec_e2prom_client-adapter,e2prom_msg,1);return static ssize_t gec_i2cdev_read(struct file *file, const char _user *buf, size_t count, loff_t *opps)int ret;/*1.构建两个msg结构体*/struct i2c_msg e2prom_msg2;wbuf0=0x0;/*2先发片内地址*/e2prom_mes0.addr = gec_e2prom_client-addr;e2prom_mes0.flags = 0;e2prom_mes0.len = 1；e2prom_mes0.buf = &wbuf0;/*3 读数据 msg*/e2prom_mes1.addr = gec_e2prom_client-addr;e2prom_mes1.flags = I2C_M_RD;/1e2prom_mes1.len = count；e2prom_mes1.buf = rbut;/*发送MSG数据到底层*/i2c_transfer(gec_e2prom_client-adapter,e2prom_msg,2);ret = copy_to_user(buf,rbut,count);return 0;static const struct file_operations gec_i2cdev_fops = .owner= THIS_MODULE,.read= gec_i2cdev_read,.write= gec_i2cdev_write,;/*调用此函数，说明设备存在， *设备存在就应该构建一个结构体来描述 */static int gec_e2prom_detect(struct i2c_adapter *adap,int address,int kind)/*1，构建一个i2c_client来描述此设备*/*放到全局变量去了*/gec_e2prom_client = kmalloc(sizeof(struct i2c_client),GFP_KERNEL);/*2，设置此结构体*/gec_e2prom_client-addr =0x50;gec_e2prom_client-adapter = adap;gec_e2prom_client-driver = &gec_i2cdev_driver;/*3，加载此结构体*/i2c_attach_client(gec_e2prom_client);return 0;static struct i2c_driver gec_i2cdev_driver = .driver = .name= gec_e2prom_driver,.attach_adapter= gec_i2cdev_attach_adapter,.detach_adapter= gec_i2cdev_detach_adapter,;/*检测设备是否存在,利用adpa发地址数据,如果有响应，则设备存在，* 设备存在则调用gec_e2prom_detect函数*/static int gec_i2cdev_attach_adapter (struct i2c_adapter *adap)/*调用probe函数实现上述功能*/i2c_probe(adap,&gec_e2prom_address_data,gec_e2prom_detect);return 0;static int gec_i2cdev_detach_adapter (struct i2c_adapter *adap)/kfree(gec_e2prom_client);return 0;static int gec_e2prom_init(void)/*1,向上层提供接口*/gec_e2prom_major = register_chrdev(0,gec_i2c_e2prom,gec_i2cdev_fops);/*2,创建设备文件*/gec_dev_class = class_create(THIS_MODULE,gec_dev_class);device_create(gec_dev_class,NULL,MKDEV(gec_e2prom_major,0),NULL,gec_e2prom);/*加载一个I2C驱动*/i2_add_driver(&gec_i2cdev_driver);return 0;static void gec_e2prom_exit(void)unregister_chrdev(gec_e2prom_major,gec_i2c_e2prom);device_destroy(gec_dev_class,MKDEV(gec_e2prom_major,0);class_destroy(gec_dev_class);i2c_del_driver(&gec_i2cdev_driver);module_init(gec_e2prom_init);module_exit(gec_e2prom_exit);MODULE_LICENSE(GPL);/*/应用程序/* * ./xx s val