/* * mmap.c -- memory mapping for the scullc char module */#ifndef __KERNEL__#  define __KERNEL__#endif#ifndef MODULE#  define MODULE#endif#include <linux/config.h>#include <linux/module.h>#include <linux/version.h>#include <linux/mm.h>     /* everything */#include <linux/errno.h>  /* error codes */#include <asm/pgtable.h>#include "scullc.h"        /* local definitions *//* * Don't try to compile mmap on the Sparc: symbols are not exported (FIXME:?) * Nor with old kernels, as the structures were different */#ifndef __sparc__/* * open and close: just keep track of how many times the device is * mapped, to avoid releasing it. */void scullc_vma_open(struct vm_area_struct *vma){    struct inode *inode = INODE_FROM_F(vma->vm_file);    ScullC_Dev *dev = scullc_devices + MINOR(inode->i_rdev);    dev->vmas++;    MOD_INC_USE_COUNT;}void scullc_vma_close(struct vm_area_struct *vma){    struct inode *inode = INODE_FROM_F(vma->vm_file);    ScullC_Dev *dev = scullc_devices + MINOR(inode->i_rdev);    dev->vmas--;    MOD_DEC_USE_COUNT;}/* * The nopage method: the core of the file. It retrieves the * page required from the scullc device and returns it to the * user. The count for the page must be incremented, because * it is automatically decremented at page unmap. * * For this reason, "order" must be zero. Otherwise, only the first * page has its count incremented, and the allocating module must * release it as a whole block. Therefore, it isn't possible to map * pages from a multipage block: when they are unmapped, their count * is individually decreased, and would drop to 0. */struct page *scullc_vma_nopage(struct vm_area_struct *vma,                                unsigned long address, int write){    unsigned long offset;    struct inode *inode = INODE_FROM_F(vma->vm_file);    ScullC_Dev *ptr, *dev = scullc_devices + MINOR(inode->i_rdev);    struct page *page = NOPAGE_SIGBUS;    void *pageptr = NULL; /* default to "missing" */    while (down_interruptible(&dev->sem))        ;  /* Can't return ERESTARTSYS here */    offset = (address - vma->vm_start) + (vma->vm_pgoff << PAGE_SHIFT);    if (offset >= dev->size) goto out; /* out of range */    /*     * Now retrieve the scullc device from the list,then the page.     * If the device has holes, the process receives a SIGBUS when     * accessing the hole.     */    offset >>= PAGE_SHIFT; /* offset is a number of pages */    for (ptr = dev; ptr && offset >= dev->qset;) {        ptr = ptr->next;        offset -= dev->qset;    }    if (ptr && ptr->data) pageptr = ptr->data[offset];    if (!pageptr) goto out; /* hole or end-of-file */    page = virt_to_page(pageptr);        /* got it, now increment the count */    atomic_inc(&page->count);out:    up(&dev->sem);    return page;}#ifdef LINUX_20_VERSIONunsigned long scullc_vma_nopage(struct vm_area_struct *vma,                                unsigned long address, int write){    unsigned long offset = address - vma->vm_start + vma->vm_offset;    ScullC_Dev *ptr, *dev = scullc_devices + MINOR(vma->vm_inode->i_rdev);    void *pageptr = NULL; /* default to "missing" */    if (offset >= dev->size) return 0; /* out of range: send SIGBUS */    /*     * Now retrieve the scullc device from the list,then the page.     * Don't want to allocate: I'm too lazy. If the device has holes,     * the process receives a SIGBUS when accessing the hole.     */    offset >>= PAGE_SHIFT; /* offset is a number of pages */    for (ptr = dev; ptr && offset >= dev->qset;) {        ptr = ptr->next;        offset -= dev->qset;    }    if (ptr && ptr->data) pageptr = ptr->data[offset];    if (!pageptr) return 0; /* hole or end-of-file: SIGBUS */    /* got it, now increment the count */    atomic_inc(&mem_map[MAP_NR(pageptr)].count);    return (unsigned long)pageptr;}#endifstruct vm_operations_struct scullc_vm_ops = {    open:     scullc_vma_open,    close:  scullc_vma_close,    nopage:   scullc_vma_nopage,};int scullc_mmap(struct file *filp, struct vm_area_struct *vma){    struct inode *inode = INODE_FROM_F(filp);    /* refuse to map if order is not 0 */    if (scullc_devices[MINOR(inode->i_rdev)].order)        return -ENODEV;#ifdef oldstuff    if (vma->vm_offset & (PAGE_SIZE-1))        return -ENXIO; /* need aligned offsets */#endif    /* don't do anything here: "nopage" will fill the holes */    vma->vm_ops = &scullc_vm_ops;    /* vma->vm_inode = inode; */    /* inode->i_count++; */    scullc_vma_open(vma);    return 0;}#else /* old or __sparc__ */int scullc_mmap(struct file *filp, struct vm_area_struct *vma){    return -ENODEV; /* like the kernel proper */}#endif /* old or __sparc__ */