【Linux裝置驅動程式（第三版）】—-裝置檔案的存取控制：獨享裝置

文章目錄

• complete.c
• Makefile
• 建立裝置節點
• 測試
• 卸載驅動

 【Linux裝置驅動程式（第三版）】----裝置檔案的存取控制：獨享裝置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_userMODULE_LICENSE("Dual BSD/GPL");#define MEMSIZE 100int complete_major = 250;DECLARE_COMPLETION(comp);unsigned char s[MEMSIZE];static atomic_t scull_s_available = ATOMIC_INIT(1);ssize_t complete_read(struct file *filp, char __user *buf, size_t size, loff_t *pos){#if 0unsigned 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;#endifwait_for_completion(&comp);return 0;}ssize_t complete_write(struct file *filp, char __user *buf, size_t size, loff_t *pos){#if 0unsigned 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;#endifreturn 0;}static int complete_open(struct inode *inode, struct file *filp){printk(KERN_DEBUG "Enter Open......");if(!atomic_dec_and_test(&scull_s_available)){atomic_inc(&scull_s_available);printk(KERN_DEBUG "Busy......");return -EBUSY;}printk(KERN_DEBUG "Open Ok......");return 0;}static int complete_release(struct inode *inode, struct file *filp){printk(KERN_DEBUG "Enter Release......");atomic_inc(&scull_s_available);return 0;}struct file_operations complete_fops = {.owner = THIS_MODULE,.read = complete_read,.write = complete_write,.open = complete_open,.release = complete_release,};int complete_init(void){printk(KERN_DEBUG "complete_init111......");int result;result = register_chrdev(complete_major, "complete", &complete_fops);if(result < 0)return result;return 0;}void complete_exit(void){printk(KERN_DEBUG "complete_exit222......");unregister_chrdev(complete_major, "complete");}module_init(complete_init);module_exit(complete_exit);

Makefile

obj-m:= complete.omodules-objs:= complete.oKDIR:= /usr/src/linux-headers-2.6.31-14-generic/PWD:= $(shell pwd)default:make -C $(KDIR) M=$(PWD) modulesclean:rm -rf *.ko *.mod.c *.mod.o *.o *.markers *.symvers *.order

建立裝置節點

mknod /dev/complete c 250 0

裝載驅動

insmod complete.ko

測試

開啟一終端，輸入：

cat /dev/complete

開啟另一終端，輸入：

cat /dev/complete

此時，終端輸出提示：裝置正忙。

卸載驅動

rmmod complete