/* * Simple - REALLY simple memory mapping demonstration. * $Id: simple.c,v 1.1 2001/01/26 20:25:15 corbet Exp $ */#ifndef __KERNEL__#  define __KERNEL__#endif#ifndef MODULE#  define MODULE#endif#include <linux/config.h>#include <linux/module.h>#include <linux/kernel.h>   /* printk() */#include <linux/malloc.h>   /* kmalloc() */#include <linux/fs.h>       /* everything... */#include <linux/errno.h>    /* error codes */#include <linux/types.h>    /* size_t */#include <linux/init.h>     /* module_init */#include <asm/page.h>#include "sysdep.h"static int simple_major = 0;MODULE_PARM(simple_major, "i");MODULE_AUTHOR("Jonathan Corbet");/* * Forwards for our methods. */int simple_open (struct inode *inode, struct file *filp);int simple_release(struct inode *inode, struct file *filp);int simple_remap_mmap(struct file *filp, struct vm_area_struct *vma);int simple_nopage_mmap(struct file *filp, struct vm_area_struct *vma);/* * Our various sub-devices. *//* Device 0 uses remap_page_range */struct file_operations simple_remap_ops = {    open:    simple_open,    release: simple_release,    mmap:    simple_remap_mmap,};/* Device 1 uses nopage */struct file_operations simple_nopage_ops = {    open:    simple_open,    release: simple_release,    mmap:    simple_nopage_mmap,};#define MAX_SIMPLE_DEV 2struct file_operations *simple_fops[MAX_SIMPLE_DEV] = {    &simple_remap_ops,    &simple_nopage_ops,};/* * Open the device; all we have to do here is to up the usage count and * set the right fops. */int simple_open (struct inode *inode, struct file *filp){    unsigned int dev = MINOR(inode->i_rdev);    if (dev >= MAX_SIMPLE_DEV)         return -ENODEV;    filp->f_op = simple_fops[dev];    MOD_INC_USE_COUNT;    return 0;}/* * Closing is even simpler. */int simple_release(struct inode *inode, struct file *filp){    MOD_DEC_USE_COUNT;    return 0;}/* * Common VMA ops. */void simple_vma_open(struct vm_area_struct *vma){ MOD_INC_USE_COUNT; }void simple_vma_close(struct vm_area_struct *vma){ MOD_DEC_USE_COUNT; }/* * The remap_page_range version of mmap. */static struct vm_operations_struct simple_remap_vm_ops = {    open:  simple_vma_open,    close: simple_vma_close,};int simple_remap_mmap(struct file *filp, struct vm_area_struct *vma){    unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;    if (offset >= __pa(high_memory) || (filp->f_flags & O_SYNC))        vma->vm_flags |= VM_IO;    vma->vm_flags |= VM_RESERVED;    if (remap_page_range(vma->vm_start, offset, vma->vm_end-vma->vm_start,                vma->vm_page_prot))        return -EAGAIN;    vma->vm_ops = &simple_remap_vm_ops;    simple_vma_open(vma);    return 0;}/* * The nopage version. */struct page *simple_vma_nopage(struct vm_area_struct *vma,                unsigned long address, int write_access){    struct page *pageptr;    unsigned long physaddr = address - vma->vm_start +            (vma->vm_pgoff << PAGE_SHIFT);    pageptr = virt_to_page(__va(physaddr));    get_page(pageptr);    return pageptr;}        static struct vm_operations_struct simple_nopage_vm_ops = {    open:    simple_vma_open,    close:   simple_vma_close,    nopage:  simple_vma_nopage,};int simple_nopage_mmap(struct file *filp, struct vm_area_struct *vma){    unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;    if (offset >= __pa(high_memory) || (filp->f_flags & O_SYNC))        vma->vm_flags |= VM_IO;    vma->vm_flags |= VM_RESERVED;    vma->vm_ops = &simple_nopage_vm_ops;    simple_vma_open(vma);    return 0;}/* * Module housekeeping. */static int simple_init(void){    int result;    result = register_chrdev(simple_major, "simple", &simple_remap_ops);    if (result < 0)    {        printk(KERN_WARNING "simple: unable to get major %d\n", simple_major);        return result;    }    if (simple_major == 0)        simple_major = result;    return 0;}static void simple_cleanup(void){    unregister_chrdev(simple_major, "simple");}module_init(simple_init);module_exit(simple_cleanup);