linux 3.0.35下globalmem 字符设备驱动实现
1、Makefile
KDIR=/home/xxx/s-linux-3.0.35 PWD:=$(shell pwd) # kernel modules obj-m := globalmem.o modules: make -C $(KDIR) M=$(PWD) modules clean: rm -rf *.o *.ko *.mod.c *.markesr *.order *.symvers .PHONY:modules clean
2、globalmem.c
#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 <linux/slab.h> #include <asm/io.h> #include <asm/system.h> #include <asm/uaccess.h> #define GLOBALMEM_SIZE 0x1000 // 4KB // create device node in the board side. // mknod /dev/globalmem c 120 0 #define GLOBALMEM_MAJOR 120 // preset major number // define ioctl cmd #define GLOBALMEM_MAGIC 0x01 #define MEM_CLEAR _IO(GLOBALMEM_MAGIC, 0) static int globalmem_major = GLOBALMEM_MAJOR; // globalmem struct struct globalmem_dev { struct cdev cdev; // cdev struct unsigned char mem[GLOBALMEM_SIZE]; // global memory }; struct globalmem_dev *globalmem_devp; // device struct instance int globalmem_open(struct inode *inode, struct file *filp) { // set device struct pointer to file privatedata pointer filp->private_data = globalmem_devp; return 0; } int globalmem_release(struct inode *inode, struct file *filp) { return 0; } static ssize_t globalmem_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 globalmem_dev *dev = filp->private_data; // get device struct pointer // analysis and get valid read length if (p >= GLOBALMEM_SIZE) // overflow return 0; if (count > GLOBALMEM_SIZE - p) // count is too large count = GLOBALMEM_SIZE - p; // kernel buf -> user buf if (copy_to_user(buf, (void *)(dev->mem + p), count)) ret = -EFAULT; else { *ppos += count; ret = count; printk(KERN_INFO "read %d bytes from %ld\n", count, p); } return ret; } static ssize_t globalmem_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 globalmem_dev *dev = filp->private_data; // get device stuct pointer // analysis and get valid write length if (p >= GLOBALMEM_SIZE) // write overflow return 0; if (count > GLOBALMEM_SIZE - p) // write count is too large count = GLOBALMEM_SIZE - p; // user buf -> kernel buf if (copy_from_user(dev->mem + p, buf, count)) ret = -EFAULT; else { *ppos += count; ret = count; printk(KERN_INFO "written %d bytes from %ld\n", count, p); } return ret; } static loff_t globalmem_llseek(struct file *filp, loff_t offset, int orig) { loff_t ret = 0; switch (orig) { case 0: // from the file head if (offset < 0 || ((unsigned int) offset > GLOBALMEM_SIZE)) { ret = -EINVAL; break; } filp->f_pos = (unsigned int) offset; ret = filp->f_pos; break; case 1: // from current position if ((filp->f_pos + offset) > GLOBALMEM_SIZE || (filp->f_pos + offset) < 0) { ret = - EINVAL; break; } filp->f_pos += offset; ret = filp->f_pos; break; } return ret; } static long globalmem_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) { struct globalmem_dev *dev = filp->private_data; // get device stuct pointer switch (cmd) { case MEM_CLEAR: memset(dev->mem, 0, GLOBALMEM_SIZE); printk(KERN_INFO "globalmem is set to zero\n"); break; default: return -EINVAL; // not supported } return 0; } // file operations struct static const struct file_operations globalmem_fops = { .owner = THIS_MODULE, .llseek = globalmem_llseek, .read = globalmem_read, .write = globalmem_write, .unlocked_ioctl = globalmem_ioctl, .open = globalmem_open, .release = globalmem_release, }; // init and add cdev struct static void globalmem_setup_cdev(struct globalmem_dev * dev, int index) { int err; int devno = MKDEV(globalmem_major, 0); cdev_init(&dev->cdev, &globalmem_fops); err = cdev_add(&dev->cdev, devno, 1); if (err) printk(KERN_NOTICE "Error %d adding globalmem", err); } // globalmem device init function int globalmem_init(void) { int result; dev_t devno = MKDEV(globalmem_major, 0); // apply globalmem device kernel region if (globalmem_major) result = register_chrdev_region(devno, 1, "globalmem"); else { // get major no dynamically result = alloc_chrdev_region(&devno, 0, 1, "globalmem"); globalmem_major = MAJOR(devno); } if (result < 0) return result; // apply device struct memory globalmem_devp = kmalloc(sizeof(struct globalmem_dev), GFP_KERNEL); if (!globalmem_devp) { result = - ENOMEM; goto fail_malloc; } memset(globalmem_devp, 0, sizeof(struct globalmem_dev)); globalmem_setup_cdev(globalmem_devp, 0); return 0; fail_malloc: unregister_chrdev_region(devno, 1); return result; } // globalmem device exit function void globalmem_exit(void) { // del cdev struct cdev_del(&globalmem_devp->cdev); // free device struct memory kfree(globalmem_devp); // unregister device region unregister_chrdev_region(MKDEV(globalmem_major, 0), 1); } module_param(globalmem_major, int, S_IRUGO); module_init(globalmem_init); module_exit(globalmem_exit); MODULE_AUTHOR("TT <[email protected]>"); MODULE_LICENSE("Dual BSD/GPL");
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