【Linux设备驱动程序(第三版)】----完成量completion
complete.c
#include <linux/init.h> #include <linux/module.h> #include <linux/sched.h> #include <linux/kernel.h> #include <linux/types.h> #include <linux/fs.h>//file_operations, file #include <linux/completion.h> #include <asm/uaccess.h>//copy_to_user & copy_from_user MODULE_LICENSE("Dual BSD/GPL"); #define MEMSIZE 100 int complete_major = 250; DECLARE_COMPLETION(comp); unsigned char s[MEMSIZE]; ssize_t complete_read(struct file *filp, char __user *buf, size_t size, loff_t *pos) { unsigned long p = *pos; unsigned int count = size; int ret = 0; if(p >= MEMSIZE) return 0; if(count > MEMSIZE - p) count = MEMSIZE -p; wait_for_completion(&comp); if(copy_to_user(buf, (void*)(s + p), count)){ return -EFAULT; } *pos += count; ret = count; return ret; } ssize_t complete_write(struct file *filp, char __user *buf, size_t size, loff_t *pos) { unsigned long p = *pos; unsigned int count = size; int ret = 0; if(p >= MEMSIZE) return 0; if(count > MEMSIZE - p) count = MEMSIZE -p; if(copy_from_user(s + p, buf, count)){ return -EFAULT; } *pos += count; ret = count; complete(&comp); return ret; } struct file_operations complete_fops = { .owner = THIS_MODULE, .read = complete_read, .write = complete_write, }; int complete_init(void) { int result; result = register_chrdev(complete_major, "complete", &complete_fops); if(result < 0) return result; return 0; } void complete_exit(void) { unregister_chrdev(complete_major, "complete"); } module_init(complete_init); module_exit(complete_exit);
Makefie
obj-m:= complete.o modules-objs:= complete.o KDIR:= /usr/src/linux-headers-2.6.31-14-generic/ PWD:= $(shell pwd) default: make -C $(KDIR) M=$(PWD) modules clean: rm -rf *.ko *.mod.c *.mod.o *.o *.markers *.symvers *.order
mknod /dev/complete c 250 0
装载
insmod complete.ko
测试
cat /dev/complete
此时,读线程会进入休眠。
打开另一个终端输入:
echo "Test" > /dev/complete
此时,读线程运行,并输出结果:“Test”
卸载
rmmod complete