Linux原子操作

1、實驗十 原子操作實驗目的掌握字符設(shè)備驅(qū)動程序編寫的框架；掌握內(nèi)核中原子操作函數(shù)的使用；實驗原理內(nèi)核提供了兩組原子操作接口（整數(shù)原子操作、位原子操作)。原子整數(shù)操作函數(shù)：atomic_inlt(int i)在聲明一個atomic_t變量時，將它初始化為iint atomic_read(atomic_t *v)原子地讀取整數(shù)變量vvoid atomic_set(atomic_t *v, int i)原子地設(shè)置v值為1void atomtic_add(int i,atomic_t *v)原子地給v加ivoid atomic_sub(int i,atomic_t *v)原子地從v減ivoid atom

2、ic_inc(atomic_t *v)原子地給v加1void atomic_dec(atomic_t *v)原子地從v減1int atomic_sub_and_test(int i, atomic_t *v) 原子地從v減i，如果結(jié)果等于o返回真；否則返回假int atomtic_add_negative(int i，atomic_t *v) 原子地給v加i，如果結(jié)果是負數(shù)，返回真；否則返回假int atomic_dec_and_test(atomic_t *v) 原子地給v減1，如果結(jié)果是o，返回真；否則返回假int atomic_inc_and_test(atomic_t *v) 原子地給

3、v加1，如果結(jié)果是o，返回真；否則返回假實驗內(nèi)容修改tiny4412開發(fā)板上的led燈驅(qū)動程序（基于實驗八）；使用應用層打開設(shè)備文件時，同一時間，只能有一個進程能夠使用該文件。一個進程打開設(shè)備文件后，另外一個進程打不開這個設(shè)備文件。leddrv：#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include volatile unsigned long *vir_gpm4con;volati

4、le unsigned long *vir_gpm4dat;static atomic_t led_atomic = atomic_init(1);static int led_open(struct inode *in,struct file *fp)if(!atomic_dec_and_test(&led_atomic)atomic_inc(&led_atomic);return -ebusy;*vir_gpm4con &= 0xffff;*vir_gpm4con |= 0x1111;*vir_gpm4dat &= 0xf; printk(all led on!n);return 0;st

5、atic int led_release(struct inode *in,struct file *fp)atomic_inc(&led_atomic);*vir_gpm4dat |= 0xf;printk(all led off!n);return 0;static unsigned char led_state=0;static ssize_t led_write(struct file *fp, const char _user *buf, size_t len, loff_t *offset)copy_from_user(&led_state, buf, 1);*vir_gpm4da

6、t = led_state;return 1;static ssize_t led_read(struct file *fp, char _user *buf, size_t len, loff_t * offset)if(led_state&(10) led_state = 1;else if(led_state&(11) led_state = 2;else if(led_state&(12) led_state = 3;else if(led_state&(1owner=this_module;cdev_add(led_drv_cdev,dev, 1);led_class = class

7、_create(this_module,led_dir);/sys/class/led_dir/device_create(led_class, null, dev, null,led_dev_file);/dev/led_dev_filereturn 0;static void _exit led_drv_exit(void)device_destroy(led_class, dev);class_destroy(led_class);cdev_del(led_drv_cdev);unregister_chrdev_region(dev, 1);iounmap(vir_gpm4con);mo

8、dule_init(led_drv_init);module_exit(led_drv_exit);module_license(gpl);ledtest:#include #include /#include #include /#include int main(int argc, char *argv) int i=0;unsigned char val = 1;unsigned char led_state=0;int fd = open(/dev/led_dev_file,o_rdwr);if(fd0)perror(open fail!n);exit(1);sleep(1);for(i=0;i12;i+)write(fd,&val,1);sleep(1);read(fd,&led_state,1);/printf(led%d is on!n,led_state);val = val 8)val = 1;close(fd);sleep(1);return 0