Linux Device Drivers 3 examples

6 files changed, 927 insertions, 0 deletions

diff --git a/scullc/Makefile b/scullc/Makefile
new file mode 100644
index 0000000..9b90b41
--- /dev/null
+++ b/scullc/Makefile
@@ -0,0 +1,46 @@
+
+# Comment/uncomment the following line to enable/disable debugging
+#DEBUG = y
+
+
+ifeq ($(DEBUG),y)
+  DEBFLAGS = -O -g -DSCULLC_DEBUG # "-O" is needed to expand inlines
+else
+  DEBFLAGS = -O2
+endif
+
+CFLAGS += $(DEBFLAGS) -I$(LDDINC)
+
+TARGET = scullc
+
+ifneq ($(KERNELRELEASE),)
+
+scullc-objs := main.o
+
+obj-m	:= scullc.o
+
+else
+
+KERNELDIR ?= /lib/modules/$(shell uname -r)/build
+PWD       := $(shell pwd)
+
+modules:
+	$(MAKE) -C $(KERNELDIR) M=$(PWD) LDDINC=$(PWD) modules
+
+endif
+
+
+install:
+	install -d $(INSTALLDIR)
+	install -c $(TARGET).o $(INSTALLDIR)
+
+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
diff --git a/scullc/main.c b/scullc/main.c
new file mode 100644
index 0000000..f7a1ca5
--- /dev/null
+++ b/scullc/main.c
@@ -0,0 +1,600 @@
+/* -*- C -*-
+ * main.c -- the bare scullc char module
+ *
+ * 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: _main.c.in,v 1.21 2004/10/14 20:11:39 corbet 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/proc_fs.h>
+#include <linux/fcntl.h>	/* O_ACCMODE */
+#include <linux/aio.h>
+#include <asm/uaccess.h>
+#include "scullc.h"		/* local definitions */
+
+
+int scullc_major =   SCULLC_MAJOR;
+int scullc_devs =    SCULLC_DEVS;	/* number of bare scullc devices */
+int scullc_qset =    SCULLC_QSET;
+int scullc_quantum = SCULLC_QUANTUM;
+
+module_param(scullc_major, int, 0);
+module_param(scullc_devs, int, 0);
+module_param(scullc_qset, int, 0);
+module_param(scullc_quantum, int, 0);
+MODULE_AUTHOR("Alessandro Rubini");
+MODULE_LICENSE("Dual BSD/GPL");
+
+struct scullc_dev *scullc_devices; /* allocated in scullc_init */
+
+int scullc_trim(struct scullc_dev *dev);
+void scullc_cleanup(void);
+
+/* declare one cache pointer: use it for all devices */
+kmem_cache_t *scullc_cache;
+
+
+
+
+
+#ifdef SCULLC_USE_PROC /* don't waste space if unused */
+/*
+ * The proc filesystem: function to read and entry
+ */
+
+void scullc_proc_offset(char *buf, char **start, off_t *offset, int *len)
+{
+	if (*offset == 0)
+		return;
+	if (*offset >= *len) {
+		/* Not there yet */
+		*offset -= *len;
+		*len = 0;
+	} else {
+		/* We're into the interesting stuff now */
+		*start = buf + *offset;
+		*offset = 0;
+	}
+}
+
+/* FIXME: Do we need this here??  It be ugly  */
+int scullc_read_procmem(char *buf, char **start, off_t offset,
+                   int count, int *eof, void *data)
+{
+	int i, j, quantum, qset, len = 0;
+	int limit = count - 80; /* Don't print more than this */
+	struct scullc_dev *d;
+
+	*start = buf;
+	for(i = 0; i < scullc_devs; i++) {
+		d = &scullc_devices[i];
+		if (down_interruptible (&d->sem))
+			return -ERESTARTSYS;
+		qset = d->qset;  /* retrieve the features of each device */
+		quantum=d->quantum;
+		len += sprintf(buf+len,"\nDevice %i: qset %i, quantum %i, sz %li\n",
+				i, qset, quantum, (long)(d->size));
+		for (; d; d = d->next) { /* scan the list */
+			len += sprintf(buf+len,"  item at %p, qset at %p\n",d,d->data);
+			scullc_proc_offset (buf, start, &offset, &len);
+			if (len > limit)
+				goto out;
+			if (d->data && !d->next) /* dump only the last item - save space */
+				for (j = 0; j < qset; j++) {
+					if (d->data[j])
+						len += sprintf(buf+len,"    % 4i:%8p\n",j,d->data[j]);
+					scullc_proc_offset (buf, start, &offset, &len);
+					if (len > limit)
+						goto out;
+				}
+		}
+	  out:
+		up (&scullc_devices[i].sem);
+		if (len > limit)
+			break;
+	}
+	*eof = 1;
+	return len;
+}
+
+#endif /* SCULLC_USE_PROC */
+
+/*
+ * Open and close
+ */
+
+int scullc_open (struct inode *inode, struct file *filp)
+{
+	struct scullc_dev *dev; /* device information */
+
+	/*  Find the device */
+	dev = container_of(inode->i_cdev, struct scullc_dev, cdev);
+
+    	/* now trim to 0 the length of the device if open was write-only */
+	if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) {
+		if (down_interruptible (&dev->sem))
+			return -ERESTARTSYS;
+		scullc_trim(dev); /* ignore errors */
+		up (&dev->sem);
+	}
+
+	/* and use filp->private_data to point to the device data */
+	filp->private_data = dev;
+
+	return 0;          /* success */
+}
+
+int scullc_release (struct inode *inode, struct file *filp)
+{
+	return 0;
+}
+
+/*
+ * Follow the list 
+ */
+struct scullc_dev *scullc_follow(struct scullc_dev *dev, int n)
+{
+	while (n--) {
+		if (!dev->next) {
+			dev->next = kmalloc(sizeof(struct scullc_dev), GFP_KERNEL);
+			memset(dev->next, 0, sizeof(struct scullc_dev));
+		}
+		dev = dev->next;
+		continue;
+	}
+	return dev;
+}
+
+/*
+ * Data management: read and write
+ */
+
+ssize_t scullc_read (struct file *filp, char __user *buf, size_t count,
+                loff_t *f_pos)
+{
+	struct scullc_dev *dev = filp->private_data; /* the first listitem */
+	struct scullc_dev *dptr;
+	int quantum = dev->quantum;
+	int qset = dev->qset;
+	int itemsize = quantum * qset; /* how many bytes in the listitem */
+	int item, s_pos, q_pos, rest;
+	ssize_t retval = 0;
+
+	if (down_interruptible (&dev->sem))
+		return -ERESTARTSYS;
+	if (*f_pos > dev->size) 
+		goto nothing;
+	if (*f_pos + count > dev->size)
+		count = dev->size - *f_pos;
+	/* find listitem, qset index, and offset in the quantum */
+	item = ((long) *f_pos) / itemsize;
+	rest = ((long) *f_pos) % itemsize;
+	s_pos = rest / quantum; q_pos = rest % quantum;
+
+    	/* follow the list up to the right position (defined elsewhere) */
+	dptr = scullc_follow(dev, item);
+
+	if (!dptr->data)
+		goto nothing; /* don't fill holes */
+	if (!dptr->data[s_pos])
+		goto nothing;
+	if (count > quantum - q_pos)
+		count = quantum - q_pos; /* read only up to the end of this quantum */
+
+	if (copy_to_user (buf, dptr->data[s_pos]+q_pos, count)) {
+		retval = -EFAULT;
+		goto nothing;
+	}
+	up (&dev->sem);
+
+	*f_pos += count;
+	return count;
+
+  nothing:
+	up (&dev->sem);
+	return retval;
+}
+
+
+
+ssize_t scullc_write (struct file *filp, const char __user *buf, size_t count,
+                loff_t *f_pos)
+{
+	struct scullc_dev *dev = filp->private_data;
+	struct scullc_dev *dptr;
+	int quantum = dev->quantum;
+	int qset = dev->qset;
+	int itemsize = quantum * qset;
+	int item, s_pos, q_pos, rest;
+	ssize_t retval = -ENOMEM; /* our most likely error */
+
+	if (down_interruptible (&dev->sem))
+		return -ERESTARTSYS;
+
+	/* find listitem, qset index and offset in the quantum */
+	item = ((long) *f_pos) / itemsize;
+	rest = ((long) *f_pos) % itemsize;
+	s_pos = rest / quantum; q_pos = rest % quantum;
+
+	/* follow the list up to the right position */
+	dptr = scullc_follow(dev, item);
+	if (!dptr->data) {
+		dptr->data = kmalloc(qset * sizeof(void *), GFP_KERNEL);
+		if (!dptr->data)
+			goto nomem;
+		memset(dptr->data, 0, qset * sizeof(char *));
+	}
+	/* Allocate a quantum using the memory cache */
+	if (!dptr->data[s_pos]) {
+		dptr->data[s_pos] = kmem_cache_alloc(scullc_cache, GFP_KERNEL);
+		if (!dptr->data[s_pos])
+			goto nomem;
+		memset(dptr->data[s_pos], 0, scullc_quantum);
+	}
+	if (count > quantum - q_pos)
+		count = quantum - q_pos; /* write only up to the end of this quantum */
+	if (copy_from_user (dptr->data[s_pos]+q_pos, buf, count)) {
+		retval = -EFAULT;
+		goto nomem;
+	}
+	*f_pos += count;
+ 
+    	/* update the size */
+	if (dev->size < *f_pos)
+		dev->size = *f_pos;
+	up (&dev->sem);
+	return count;
+
+  nomem:
+	up (&dev->sem);
+	return retval;
+}
+
+/*
+ * The ioctl() implementation
+ */
+
+int scullc_ioctl (struct inode *inode, struct file *filp,
+                 unsigned int cmd, unsigned long arg)
+{
+
+	int err = 0, ret = 0, tmp;
+
+	/* don't even decode wrong cmds: better returning  ENOTTY than EFAULT */
+	if (_IOC_TYPE(cmd) != SCULLC_IOC_MAGIC) return -ENOTTY;
+	if (_IOC_NR(cmd) > SCULLC_IOC_MAXNR) return -ENOTTY;
+
+	/*
+	 * the type is a bitmask, and VERIFY_WRITE catches R/W
+	 * transfers. Note that the type is user-oriented, while
+	 * verify_area is kernel-oriented, so the concept of "read" and
+	 * "write" is reversed
+	 */
+	if (_IOC_DIR(cmd) & _IOC_READ)
+		err = !access_ok(VERIFY_WRITE, (void __user *)arg, _IOC_SIZE(cmd));
+	else if (_IOC_DIR(cmd) & _IOC_WRITE)
+		err =  !access_ok(VERIFY_READ, (void __user *)arg, _IOC_SIZE(cmd));
+	if (err)
+		return -EFAULT;
+
+	switch(cmd) {
+
+	case SCULLC_IOCRESET:
+		scullc_qset = SCULLC_QSET;
+		scullc_quantum = SCULLC_QUANTUM;
+		break;
+
+	case SCULLC_IOCSQUANTUM: /* Set: arg points to the value */
+		ret = __get_user(scullc_quantum, (int __user *) arg);
+		break;
+
+	case SCULLC_IOCTQUANTUM: /* Tell: arg is the value */
+		scullc_quantum = arg;
+		break;
+
+	case SCULLC_IOCGQUANTUM: /* Get: arg is pointer to result */
+		ret = __put_user (scullc_quantum, (int __user *) arg);
+		break;
+
+	case SCULLC_IOCQQUANTUM: /* Query: return it (it's positive) */
+		return scullc_quantum;
+
+	case SCULLC_IOCXQUANTUM: /* eXchange: use arg as pointer */
+		tmp = scullc_quantum;
+		ret = __get_user(scullc_quantum, (int __user *) arg);
+		if (ret == 0)
+			ret = __put_user(tmp, (int __user *) arg);
+		break;
+
+	case SCULLC_IOCHQUANTUM: /* sHift: like Tell + Query */
+		tmp = scullc_quantum;
+		scullc_quantum = arg;
+		return tmp;
+
+	case SCULLC_IOCSQSET:
+		ret = __get_user(scullc_qset, (int __user *) arg);
+		break;
+
+	case SCULLC_IOCTQSET:
+		scullc_qset = arg;
+		break;
+
+	case SCULLC_IOCGQSET:
+		ret = __put_user(scullc_qset, (int __user *)arg);
+		break;
+
+	case SCULLC_IOCQQSET:
+		return scullc_qset;
+
+	case SCULLC_IOCXQSET:
+		tmp = scullc_qset;
+		ret = __get_user(scullc_qset, (int __user *)arg);
+		if (ret == 0)
+			ret = __put_user(tmp, (int __user *)arg);
+		break;
+
+	case SCULLC_IOCHQSET:
+		tmp = scullc_qset;
+		scullc_qset = arg;
+		return tmp;
+
+	default:  /* redundant, as cmd was checked against MAXNR */
+		return -ENOTTY;
+	}
+
+	return ret;
+}
+
+/*
+ * The "extended" operations
+ */
+
+loff_t scullc_llseek (struct file *filp, loff_t off, int whence)
+{
+	struct scullc_dev *dev = filp->private_data;
+	long newpos;
+
+	switch(whence) {
+	case 0: /* SEEK_SET */
+		newpos = off;
+		break;
+
+	case 1: /* SEEK_CUR */
+		newpos = filp->f_pos + off;
+		break;
+
+	case 2: /* SEEK_END */
+		newpos = dev->size + off;
+		break;
+
+	default: /* can't happen */
+		return -EINVAL;
+	}
+	if (newpos<0) return -EINVAL;
+	filp->f_pos = newpos;
+	return newpos;
+}
+
+
+/*
+ * A simple asynchronous I/O implementation.
+ */
+
+struct async_work {
+	struct kiocb *iocb;
+	int result;
+	struct work_struct work;
+};
+
+/*
+ * "Complete" an asynchronous operation.
+ */
+static void scullc_do_deferred_op(void *p)
+{
+	struct async_work *stuff = (struct async_work *) p;
+	aio_complete(stuff->iocb, stuff->result, 0);
+	kfree(stuff);
+}
+
+
+static int scullc_defer_op(int write, struct kiocb *iocb, char __user *buf,
+		size_t count, loff_t pos)
+{
+	struct async_work *stuff;
+	int result;
+
+	/* Copy now while we can access the buffer */
+	if (write)
+		result = scullc_write(iocb->ki_filp, buf, count, &pos);
+	else
+		result = scullc_read(iocb->ki_filp, buf, count, &pos);
+
+	/* If this is a synchronous IOCB, we return our status now. */
+	if (is_sync_kiocb(iocb))
+		return result;
+
+	/* Otherwise defer the completion for a few milliseconds. */
+	stuff = kmalloc (sizeof (*stuff), GFP_KERNEL);
+	if (stuff == NULL)
+		return result; /* No memory, just complete now */
+	stuff->iocb = iocb;
+	stuff->result = result;
+	INIT_WORK(&stuff->work, scullc_do_deferred_op, stuff);
+	schedule_delayed_work(&stuff->work, HZ/100);
+	return -EIOCBQUEUED;
+}
+
+
+static ssize_t scullc_aio_read(struct kiocb *iocb, char __user *buf, size_t count,
+		loff_t pos)
+{
+	return scullc_defer_op(0, iocb, buf, count, pos);
+}
+
+static ssize_t scullc_aio_write(struct kiocb *iocb, const char __user *buf,
+		size_t count, loff_t pos)
+{
+	return scullc_defer_op(1, iocb, (char __user *) buf, count, pos);
+}
+
+
+ 
+
+/*
+ * The fops
+ */
+
+struct file_operations scullc_fops = {
+	.owner =     THIS_MODULE,
+	.llseek =    scullc_llseek,
+	.read =	     scullc_read,
+	.write =     scullc_write,
+	.ioctl =     scullc_ioctl,
+	.open =	     scullc_open,
+	.release =   scullc_release,
+	.aio_read =  scullc_aio_read,
+	.aio_write = scullc_aio_write,
+};
+
+int scullc_trim(struct scullc_dev *dev)
+{
+	struct scullc_dev *next, *dptr;
+	int qset = dev->qset;   /* "dev" is not-null */
+	int i;
+
+	if (dev->vmas) /* don't trim: there are active mappings */
+		return -EBUSY;
+
+	for (dptr = dev; dptr; dptr = next) { /* all the list items */
+		if (dptr->data) {
+			for (i = 0; i < qset; i++)
+				if (dptr->data[i])
+					kmem_cache_free(scullc_cache, dptr->data[i]);
+
+			kfree(dptr->data);
+			dptr->data=NULL;
+		}
+		next=dptr->next;
+		if (dptr != dev) kfree(dptr); /* all of them but the first */
+	}
+	dev->size = 0;
+	dev->qset = scullc_qset;
+	dev->quantum = scullc_quantum;
+	dev->next = NULL;
+	return 0;
+}
+
+
+static void scullc_setup_cdev(struct scullc_dev *dev, int index)
+{
+	int err, devno = MKDEV(scullc_major, index);
+    
+	cdev_init(&dev->cdev, &scullc_fops);
+	dev->cdev.owner = THIS_MODULE;
+	dev->cdev.ops = &scullc_fops;
+	err = cdev_add (&dev->cdev, devno, 1);
+	/* Fail gracefully if need be */
+	if (err)
+		printk(KERN_NOTICE "Error %d adding scull%d", err, index);
+}
+
+
+
+/*
+ * Finally, the module stuff
+ */
+
+int scullc_init(void)
+{
+	int result, i;
+	dev_t dev = MKDEV(scullc_major, 0);
+	
+	/*
+	 * Register your major, and accept a dynamic number.
+	 */
+	if (scullc_major)
+		result = register_chrdev_region(dev, scullc_devs, "scullc");
+	else {
+		result = alloc_chrdev_region(&dev, 0, scullc_devs, "scullc");
+		scullc_major = MAJOR(dev);
+	}
+	if (result < 0)
+		return result;
+
+	
+	/* 
+	 * allocate the devices -- we can't have them static, as the number
+	 * can be specified at load time
+	 */
+	scullc_devices = kmalloc(scullc_devs*sizeof (struct scullc_dev), GFP_KERNEL);
+	if (!scullc_devices) {
+		result = -ENOMEM;
+		goto fail_malloc;
+	}
+	memset(scullc_devices, 0, scullc_devs*sizeof (struct scullc_dev));
+	for (i = 0; i < scullc_devs; i++) {
+		scullc_devices[i].quantum = scullc_quantum;
+		scullc_devices[i].qset = scullc_qset;
+		sema_init (&scullc_devices[i].sem, 1);
+		scullc_setup_cdev(scullc_devices + i, i);
+	}
+
+	scullc_cache = kmem_cache_create("scullc", scullc_quantum,
+			0, SLAB_HWCACHE_ALIGN, NULL, NULL); /* no ctor/dtor */
+	if (!scullc_cache) {
+		scullc_cleanup();
+		return -ENOMEM;
+	}
+
+#ifdef SCULLC_USE_PROC /* only when available */
+	create_proc_read_entry("scullcmem", 0, NULL, scullc_read_procmem, NULL);
+#endif
+	return 0; /* succeed */
+
+  fail_malloc:
+	unregister_chrdev_region(dev, scullc_devs);
+	return result;
+}
+
+
+
+void scullc_cleanup(void)
+{
+	int i;
+
+#ifdef SCULLC_USE_PROC
+	remove_proc_entry("scullcmem", NULL);
+#endif
+
+	for (i = 0; i < scullc_devs; i++) {
+		cdev_del(&scullc_devices[i].cdev);
+		scullc_trim(scullc_devices + i);
+	}
+	kfree(scullc_devices);
+
+	if (scullc_cache)
+		kmem_cache_destroy(scullc_cache);
+	unregister_chrdev_region(MKDEV (scullc_major, 0), scullc_devs);
+}
+
+
+module_init(scullc_init);
+module_exit(scullc_cleanup);
diff --git a/scullc/mmap.c b/scullc/mmap.c
new file mode 100644
index 0000000..841f62c
--- /dev/null
+++ b/scullc/mmap.c
@@ -0,0 +1,118 @@
+/*  -*- C -*-
+ * mmap.c -- memory mapping for the scullc char module
+ *
+ * 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: _mmap.c.in,v 1.13 2004/10/18 18:07:36 corbet Exp $
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+
+#include <linux/mm.h>		/* everything */
+#include <linux/errno.h>	/* error codes */
+#include <asm/pgtable.h>
+
+#include "scullc.h"		/* local definitions */
+
+
+/*
+ * 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 scullc_dev *dev = vma->vm_private_data;
+
+	dev->vmas++;
+}
+
+void scullc_vma_close(struct vm_area_struct *vma)
+{
+	struct scullc_dev *dev = vma->vm_private_data;
+
+	dev->vmas--;
+}
+
+/*
+ * 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 *type)
+{
+	unsigned long offset;
+	struct scullc_dev *ptr, *dev = vma->vm_private_data;
+	struct page *page = NOPAGE_SIGBUS;
+	void *pageptr = NULL; /* default to "missing" */
+
+	down(&dev->sem);
+	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 */
+
+	/* got it, now increment the count */
+	get_page(page);
+	if (type)
+		*type = VM_FAULT_MINOR;
+  out:
+	up(&dev->sem);
+	return page;
+}
+
+
+
+struct 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 = filp->f_dentry->d_inode;
+
+	/* refuse to map if order is not 0 */
+	if (scullc_devices[iminor(inode)].order)
+		return -ENODEV;
+
+	/* don't do anything here: "nopage" will set up page table entries */
+	vma->vm_ops = &scullc_vm_ops;
+	vma->vm_flags |= VM_RESERVED;
+	vma->vm_private_data = filp->private_data;
+	scullc_vma_open(vma);
+	return 0;
+}
+
diff --git a/scullc/scullc.h b/scullc/scullc.h
new file mode 100644
index 0000000..86d5090
--- /dev/null
+++ b/scullc/scullc.h
@@ -0,0 +1,122 @@
+/* -*- C -*-
+ * scullc.h -- definitions for the scullc char module
+ *
+ * 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.
+ */
+
+#include <linux/ioctl.h>
+#include <linux/cdev.h>
+
+/*
+ * Macros to help debugging
+ */
+
+#undef PDEBUG             /* undef it, just in case */
+#ifdef SCULLC_DEBUG
+#  ifdef __KERNEL__
+     /* This one if debugging is on, and kernel space */
+#    define PDEBUG(fmt, args...) printk( KERN_DEBUG "scullc: " fmt, ## args)
+#  else
+     /* This one for user space */
+#    define PDEBUG(fmt, args...) fprintf(stderr, fmt, ## args)
+#  endif
+#else
+#  define PDEBUG(fmt, args...) /* not debugging: nothing */
+#endif
+
+#undef PDEBUGG
+#define PDEBUGG(fmt, args...) /* nothing: it's a placeholder */
+
+#define SCULLC_MAJOR 0   /* dynamic major by default */
+
+#define SCULLC_DEVS 4    /* scullc0 through scullc3 */
+
+/*
+ * The bare device is a variable-length region of memory.
+ * Use a linked list of indirect blocks.
+ *
+ * "scullc_dev->data" points to an array of pointers, each
+ * pointer refers to a memory page.
+ *
+ * The array (quantum-set) is SCULLC_QSET long.
+ */
+#define SCULLC_QUANTUM  4000 /* use a quantum size like scull */
+#define SCULLC_QSET     500
+
+struct scullc_dev {
+	void **data;
+	struct scullc_dev *next;  /* next listitem */
+	int vmas;                 /* active mappings */
+	int quantum;              /* the current allocation size */
+	int qset;                 /* the current array size */
+	size_t size;              /* 32-bit will suffice */
+	struct semaphore sem;     /* Mutual exclusion */
+	struct cdev cdev;
+};
+
+extern struct scullc_dev *scullc_devices;
+
+extern struct file_operations scullc_fops;
+
+/*
+ * The different configurable parameters
+ */
+extern int scullc_major;     /* main.c */
+extern int scullc_devs;
+extern int scullc_order;
+extern int scullc_qset;
+
+/*
+ * Prototypes for shared functions
+ */
+int scullc_trim(struct scullc_dev *dev);
+struct scullc_dev *scullc_follow(struct scullc_dev *dev, int n);
+
+
+#ifdef SCULLC_DEBUG
+#  define SCULLC_USE_PROC
+#endif
+
+/*
+ * Ioctl definitions
+ */
+
+/* Use 'K' as magic number */
+#define SCULLC_IOC_MAGIC  'K'
+
+#define SCULLC_IOCRESET    _IO(SCULLC_IOC_MAGIC, 0)
+
+/*
+ * S means "Set" through a ptr,
+ * T means "Tell" directly
+ * G means "Get" (to a pointed var)
+ * Q means "Query", response is on the return value
+ * X means "eXchange": G and S atomically
+ * H means "sHift": T and Q atomically
+ */
+#define SCULLC_IOCSQUANTUM _IOW(SCULLC_IOC_MAGIC,  1, int)
+#define SCULLC_IOCTQUANTUM _IO(SCULLC_IOC_MAGIC,   2)
+#define SCULLC_IOCGQUANTUM _IOR(SCULLC_IOC_MAGIC,  3, int)
+#define SCULLC_IOCQQUANTUM _IO(SCULLC_IOC_MAGIC,   4)
+#define SCULLC_IOCXQUANTUM _IOWR(SCULLC_IOC_MAGIC, 5, int)
+#define SCULLC_IOCHQUANTUM _IO(SCULLC_IOC_MAGIC,   6)
+#define SCULLC_IOCSQSET    _IOW(SCULLC_IOC_MAGIC,  7, int)
+#define SCULLC_IOCTQSET    _IO(SCULLC_IOC_MAGIC,   8)
+#define SCULLC_IOCGQSET    _IOR(SCULLC_IOC_MAGIC,  9, int)
+#define SCULLC_IOCQQSET    _IO(SCULLC_IOC_MAGIC,  10)
+#define SCULLC_IOCXQSET    _IOWR(SCULLC_IOC_MAGIC,11, int)
+#define SCULLC_IOCHQSET    _IO(SCULLC_IOC_MAGIC,  12)
+
+#define SCULLC_IOC_MAXNR 12
+
+
+
diff --git a/scullc/scullc_load b/scullc/scullc_load
new file mode 100644
index 0000000..8ca1f69
--- /dev/null
+++ b/scullc/scullc_load
@@ -0,0 +1,30 @@
+#!/bin/sh
+module="scullc"
+device="scullc"
+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
+
+# remove stale nodes
+rm -f /dev/${device}? 
+
+# invoke insmod with all arguments we got
+# and use a pathname, as newer modutils don't look in . by default
+/sbin/insmod -f ./$module.ko $* || exit 1
+
+major=`cat /proc/devices | awk "\\$2==\"$module\" {print \\$1}"`
+
+mknod /dev/${device}0 c $major 0
+mknod /dev/${device}1 c $major 1
+mknod /dev/${device}2 c $major 2
+mknod /dev/${device}3 c $major 3
+ln -sf ${device}0  /dev/${device}
+
+# give appropriate group/permissions
+chgrp $group /dev/${device}[0-3]
+chmod $mode  /dev/${device}[0-3]
diff --git a/scullc/scullc_unload b/scullc/scullc_unload
new file mode 100644
index 0000000..bb91f71
--- /dev/null
+++ b/scullc/scullc_unload
@@ -0,0 +1,11 @@
+#!/bin/sh
+module="scullc"
+device="scullc"
+
+# invoke rmmod with all arguments we got
+/sbin/rmmod $module $* || exit 1
+
+# remove nodes
+rm -f /dev/${device}[0-3] /dev/${device}
+
+exit 0