140 lines
2.6 KiB
C
Executable File
140 lines
2.6 KiB
C
Executable File
#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/cdev.h>
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#include <linux/uaccess.h>
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#define VFB_MAJOR 256
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#define VFB_MINOR 1
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#define VFB_DEV_CNT 1
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#define VFB_DEV_NAME "vfbdev"
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struct vfb_dev {
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unsigned char *buf;
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struct cdev cdev;
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};
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static struct vfb_dev vfbdev;
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static int vfb_open(struct inode * inode, struct file * filp)
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{
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return 0;
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}
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static int vfb_release(struct inode *inode, struct file *filp)
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{
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return 0;
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}
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static int vfb_mmap(struct file *filp, struct vm_area_struct *vma)
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{
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if (remap_pfn_range(vma, vma->vm_start, virt_to_phys(vfbdev.buf) >> PAGE_SHIFT, \
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vma->vm_end - vma->vm_start, vma->vm_page_prot))
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return -EAGAIN;
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return 0;
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}
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ssize_t vfb_read(struct file *filp, char __user *buf, size_t count, loff_t *pos)
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{
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int ret;
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size_t len = (count > PAGE_SIZE) ? PAGE_SIZE : count;
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if (*pos + len > PAGE_SIZE)
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len = PAGE_SIZE - *pos;
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ret = copy_to_user(buf, vfbdev.buf + *pos, len);
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*pos += len - ret;
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return len - ret;
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}
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static loff_t vfb_llseek(struct file * filp, loff_t off, int whence)
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{
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loff_t newpos;
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switch (whence) {
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case SEEK_SET:
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newpos = off;
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break;
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case SEEK_CUR:
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newpos = filp->f_pos + off;
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break;
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case SEEK_END:
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newpos = PAGE_SIZE + off;
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break;
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default: /* can't happen */
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return -EINVAL;
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}
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if (newpos < 0 || newpos > PAGE_SIZE)
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return -EINVAL;
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filp->f_pos = newpos;
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return newpos;
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}
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static struct file_operations vfb_fops = {
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.owner = THIS_MODULE,
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.open = vfb_open,
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.release = vfb_release,
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.mmap = vfb_mmap,
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.read = vfb_read,
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.llseek = vfb_llseek,
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};
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static int __init vfb_init(void)
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{
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int ret;
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dev_t dev;
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unsigned long addr;
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dev = MKDEV(VFB_MAJOR, VFB_MINOR);
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ret = register_chrdev_region(dev, VFB_DEV_CNT, VFB_DEV_NAME);
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if (ret)
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goto reg_err;
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cdev_init(&vfbdev.cdev, &vfb_fops);
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vfbdev.cdev.owner = THIS_MODULE;
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ret = cdev_add(&vfbdev.cdev, dev, VFB_DEV_CNT);
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if (ret)
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goto add_err;
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addr = __get_free_page(GFP_KERNEL);
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if (!addr)
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goto get_err;
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vfbdev.buf = (unsigned char *)addr;
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memset(vfbdev.buf, 0, PAGE_SIZE);
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return 0;
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get_err:
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cdev_del(&vfbdev.cdev);
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add_err:
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unregister_chrdev_region(dev, VFB_DEV_CNT);
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reg_err:
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return ret;
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}
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static void __exit vfb_exit(void)
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{
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dev_t dev;
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dev = MKDEV(VFB_MAJOR, VFB_MINOR);
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free_page((unsigned long)vfbdev.buf);
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cdev_del(&vfbdev.cdev);
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unregister_chrdev_region(dev, VFB_DEV_CNT);
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}
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module_init(vfb_init);
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module_exit(vfb_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Kevin Jiang <jiangxg@farsight.com.cn>");
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MODULE_DESCRIPTION("This is an example for mmap");
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