Table of Contents
simple.c
/*
* Simple - REALLY simple memory mapping demonstration.
*
* Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
* Copyright (C) 2001 O'Reilly & Associates
*
* The source code in this file can be freely used, adapted,
* and redistributed in source or binary form, so long as an
* acknowledgment appears in derived source files. The citation
* should list that the code comes from the book "Linux Device
* Drivers" by Alessandro Rubini and Jonathan Corbet, published
* by O'Reilly & Associates. No warranty is attached;
* we cannot take responsibility for errors or fitness for use.
*
* $Id: simple.c,v 1.12 2005/01/31 16:15:31 rubini Exp $
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/kernel.h> /* printk() */
#include <linux/slab.h> /* kmalloc() */
#include <linux/fs.h> /* everything... */
#include <linux/errno.h> /* error codes */
#include <linux/types.h> /* size_t */
#include <linux/mm.h>
#include <linux/kdev_t.h>
#include <asm/page.h>
#include <linux/cdev.h>
#include <linux/device.h>
static int simple_major = 0;
module_param(simple_major, int, 0);
MODULE_AUTHOR("Jonathan Corbet");
MODULE_LICENSE("Dual BSD/GPL");
/*
* Open the device; in fact, there's nothing to do here.
*/
static int simple_open (struct inode *inode, struct file *filp)
{
return 0;
}
/*
* Closing is just as simpler.
*/
static int simple_release(struct inode *inode, struct file *filp)
{
return 0;
}
/*
* Common VMA ops.
*/
void simple_vma_open(struct vm_area_struct *vma)
{
printk(KERN_NOTICE "Simple VMA open, virt %lx, phys %lx\n",
vma->vm_start, vma->vm_pgoff << PAGE_SHIFT);
}
void simple_vma_close(struct vm_area_struct *vma)
{
printk(KERN_NOTICE "Simple VMA close.\n");
}
/*
* The remap_pfn_range version of mmap. This one is heavily borrowed
* from drivers/char/mem.c.
*/
static struct vm_operations_struct simple_remap_vm_ops = {
.open = simple_vma_open,
.close = simple_vma_close,
};
static int simple_remap_mmap(struct file *filp, struct vm_area_struct *vma)
{
if (remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
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 *type)
{
struct page *pageptr;
unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
unsigned long physaddr = address - vma->vm_start + offset;
unsigned long pageframe = physaddr >> PAGE_SHIFT;
// Eventually remove these printks
printk (KERN_NOTICE "---- Nopage, off %lx phys %lx\n", offset, physaddr);
printk (KERN_NOTICE "VA is %p\n", __va (physaddr));
printk (KERN_NOTICE "Page at %p\n", virt_to_page (__va (physaddr)));
if (!pfn_valid(pageframe))
return NOPAGE_SIGBUS;
pageptr = pfn_to_page(pageframe);
printk (KERN_NOTICE "page->index = %ld mapping %p\n", pageptr->index, pageptr->mapping);
printk (KERN_NOTICE "Page frame %ld\n", pageframe);
get_page(pageptr);
if (type)
*type = VM_FAULT_MINOR;
return pageptr;
}
static struct vm_operations_struct simple_nopage_vm_ops = {
.open = simple_vma_open,
.close = simple_vma_close,
.nopage = simple_vma_nopage,
};
static 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;
}
/*
* Set up the cdev structure for a device.
*/
static void simple_setup_cdev(struct cdev *dev, int minor,
struct file_operations *fops)
{
int err, devno = MKDEV(simple_major, minor);
cdev_init(dev, fops);
dev->owner = THIS_MODULE;
dev->ops = fops;
err = cdev_add (dev, devno, 1);
/* Fail gracefully if need be */
if (err)
printk (KERN_NOTICE "Error %d adding simple%d", err, minor);
}
/*
* Our various sub-devices.
*/
/* Device 0 uses remap_pfn_range */
static struct file_operations simple_remap_ops = {
.owner = THIS_MODULE,
.open = simple_open,
.release = simple_release,
.mmap = simple_remap_mmap,
};
/* Device 1 uses nopage */
static struct file_operations simple_nopage_ops = {
.owner = THIS_MODULE,
.open = simple_open,
.release = simple_release,
.mmap = simple_nopage_mmap,
};
#define MAX_SIMPLE_DEV 2
#if 0
static struct file_operations *simple_fops[MAX_SIMPLE_DEV] = {
&simple_remap_ops,
&simple_nopage_ops,
};
#endif
/*
* We export two simple devices. There's no need for us to maintain any
* special housekeeping info, so we just deal with raw cdevs.
*/
static struct cdev SimpleDevs[MAX_SIMPLE_DEV];
/*
* Module housekeeping.
*/
static int simple_init(void)
{
int result;
dev_t dev = MKDEV(simple_major, 0);
/* Figure out our device number. */
if (simple_major)
result = register_chrdev_region(dev, 2, "simple");
else {
result = alloc_chrdev_region(&dev, 0, 2, "simple");
simple_major = MAJOR(dev);
}
if (result < 0) {
printk(KERN_WARNING "simple: unable to get major %d\n", simple_major);
return result;
}
if (simple_major == 0)
simple_major = result;
/* Now set up two cdevs. */
simple_setup_cdev(SimpleDevs, 0, &simple_remap_ops);
simple_setup_cdev(SimpleDevs + 1, 1, &simple_nopage_ops);
return 0;
}
static void simple_cleanup(void)
{
cdev_del(SimpleDevs);
cdev_del(SimpleDevs + 1);
unregister_chrdev_region(MKDEV(simple_major, 0), 2);
}
module_init(simple_init);
module_exit(simple_cleanup);
simple_load
#!/bin/sh
module="simple"
device="simple"
mode="664"
# Group: since distributions do it differently, look for wheel or use staff
if grep '^staff:' /etc/group > /dev/null; then
group="staff"
else
group="wheel"
fi
# invoke insmod with all arguments we got
# and use a pathname, as newer modutils don't look in . by default
/sbin/insmod -f ./$module.ko $* || exit 1
major=`cat /proc/devices | awk "\\$2==\"$module\" {print \\$1}"`
# Remove stale nodes and replace them, then give gid and perms
# Usually the script is shorter, it's simple that has several devices in it.
rm -f /dev/${device}[rn]
mknod /dev/${device}r c $major 0
mknod /dev/${device}n c $major 1
chgrp $group /dev/${device}[rn]
chmod $mode /dev/${device}[rn]
simple_unload
#!/bin/sh
module="simple"
device="simple"
# invoke rmmod with all arguments we got
/sbin/rmmod $module $* || exit 1
# Remove stale nodes
rm -f /dev/${device}[rn] Makefile
# Comment/uncomment the following line to disable/enable debugging
#DEBUG = y
# Add your debugging flag (or not) to CFLAGS
ifeq ($(DEBUG),y)
DEBFLAGS = -O -g # "-O" is needed to expand inlines
else
DEBFLAGS = -O2
endif
CFLAGS += $(DEBFLAGS) -I$(LDDINCDIR)
ifneq ($(KERNELRELEASE),)
# call from kernel build system
obj-m := simple.o
else
KERNELDIR ?= /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
default:
$(MAKE) -C $(KERNELDIR) M=$(PWD) LDDINCDIR=$(PWD)/../include modules
endif
clean:
rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions
depend .depend dep:
$(CC) $(CFLAGS) -M *.c > .depend
ifeq (.depend,$(wildcard .depend))
include .depend
endif