mem-dev-0.20.rar_字符设备驱动

#include <linux/module.h> #include <linux/types.h> #include <linux/fs.h> #include <linux/errno.h> #include <linux/mm.h> #include <linux/sched.h> #include <linux/init.h> #include <linux/cdev.h> #include <asm/io.h> #include <asm/system.h> #include <asm/uaccess.h> #include "memdev.h" static int mem_major = 0; module_param(mem_major, int, S_IRUGO); struct mem_dev *mem_devp; struct cdev cdevp; int mem_open(struct inode *inode, struct file *filp) { struct mem_dev *dev; int num = MINOR(inode->i_rdev); if (num >= MEMDEV_NR_DEVS) return -ENODEV; dev = &mem_devp[num]; filp->private_data = dev; return 0; } int mem_release(struct inode *inode, struct file *filp) { return 0; } static ssize_t mem_read(struct file *filp, char __user *buf, size_t size, loff_t *ppos) { unsigned long p = *ppos; unsigned int count = size; int ret = 0; struct mem_dev *dev = filp->private_data; if (p >= MEMDEV_SIZE) return 0; if (count > MEMDEV_SIZE - p) count = MEMDEV_SIZE - p; if (copy_to_user(buf, (void*)(dev->data + p), count)) { ret = - EFAULT; } else { *ppos += count; ret = count; printk(KERN_INFO "read %d bytes(s) from %d\n", count, p); } return ret; } static ssize_t mem_write(struct file *filp, const char __user *buf, size_t size, loff_t *ppos) { unsigned long p = *ppos; unsigned int count = size; int ret = 0; struct mem_dev *dev = filp->private_data; if (p >= MEMDEV_SIZE) return 0; if (count > MEMDEV_SIZE - p) count = MEMDEV_SIZE - p; if (copy_from_user(dev->data + p, buf, count)) ret = - EFAULT; else { *ppos += count; ret = count; printk(KERN_INFO "written %d bytes(s) from %d\n", count, p); } return ret; } static loff_t mem_llseek(struct file *filp, loff_t offset, int whence) { loff_t newpos; switch(whence) { case 0: newpos = offset; break; case 1: newpos = filp->f_pos + offset; break; case 2: newpos = MEMDEV_SIZE -1 + offset; break; default: return -EINVAL; } if ((newpos<0) || (newpos>MEMDEV_SIZE)) return -EINVAL; filp->f_pos = newpos; return newpos; } static const struct file_operations mem_fops = { .owner = THIS_MODULE, .llseek = mem_llseek, .read = mem_read, .write = mem_write, .open = mem_open, .release = mem_release, }; static int memdev_init(void) { int result; int i; //设备编号 dev_t devno = MKDEV(mem_major, 0); //自动分配 if (mem_major) result = register_chrdev_region(devno, 2, "memdev"); else { result = alloc_chrdev_region(&devno, 0, 2, "memdev"); mem_major = MAJOR(devno);//取得主设备号 } if (result < 0) return result; cdev_init(&cdevp, &mem_fops); cdevp.owner = THIS_MODULE; cdevp.ops = &mem_fops; //通知内核 cdev_add(&cdevp, MKDEV(mem_major, 0), MEMDEV_NR_DEVS); //分配内存 mem_devp = kmalloc(MEMDEV_NR_DEVS * sizeof(struct mem_dev), GFP_KERNEL); if (!mem_devp) { result = - ENOMEM; goto fail_malloc; } memset(mem_devp, 0, sizeof(struct mem_dev)); for (i=0; i < MEMDEV_NR_DEVS; i++) { mem_devp[i].size = MEMDEV_SIZE; mem_devp[i].data = kmalloc(MEMDEV_SIZE, GFP_KERNEL); memset(mem_devp[i].data, 0, MEMDEV_SIZE); } return 0; fail_malloc: unregister_chrdev_region(devno, 1); return result; } static void memdev_exit(void) { cdev_del(&cdevp); kfree(mem_devp); unregister_chrdev_region(MKDEV(mem_major, 0), 2); } MODULE_AUTHOR("David Xie"); MODULE_LICENSE("GPL"); module_init(memdev_init); module_exit(memdev_exit);