main.c

linux设备驱动程序第三版及源代码

/*
 * main.c -- the bare scull 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/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/seq_file.h>
#include <linux/cdev.h>

#include <asm/system.h>		/* cli(), *_flags */
#include <asm/uaccess.h>	/* copy_*_user */

#include "scull.h"		/* local definitions */

/*
 * Our parameters which can be set at load time.
 */

int scull_major =   SCULL_MAJOR;
int scull_minor =   0;
int scull_nr_devs = SCULL_NR_DEVS;	/* number of bare scull devices */
int scull_quantum = SCULL_QUANTUM;
int scull_qset =    SCULL_QSET;

module_param(scull_major, int, S_IRUGO);
module_param(scull_minor, int, S_IRUGO);
module_param(scull_nr_devs, int, S_IRUGO);
module_param(scull_quantum, int, S_IRUGO);
module_param(scull_qset, int, S_IRUGO);

MODULE_AUTHOR("Alessandro Rubini, Jonathan Corbet");
MODULE_LICENSE("Dual BSD/GPL");

struct scull_dev *scull_devices;	/* allocated in scull_init_module */


/*
 * Empty out the scull device; must be called with the device
 * semaphore held.
 */
int scull_trim(struct scull_dev *dev)
{
	struct scull_qset *next, *dptr;
	int qset = dev->qset;   /* "dev" is not-null */
	int i;

	for (dptr = dev->data; dptr; dptr = next) { /* all the list items */
		if (dptr->data) {
			for (i = 0; i < qset; i++)
				kfree(dptr->data[i]);
			kfree(dptr->data);
			dptr->data = NULL;
		}
		next = dptr->next;
		kfree(dptr);
	}
	dev->size = 0;
	dev->quantum = scull_quantum;
	dev->qset = scull_qset;
	dev->data = NULL;
	return 0;
}
#ifdef SCULL_DEBUG /* use proc only if debugging */
/*
 * The proc filesystem: function to read and entry
 */

int scull_read_procmem(char *buf, char **start, off_t offset,
                   int count, int *eof, void *data)
{
	int i, j, len = 0;
	int limit = count - 80; /* Don't print more than this */

	for (i = 0; i < scull_nr_devs && len <= limit; i++) {
		struct scull_dev *d = &scull_devices[i];
		struct scull_qset *qs = d->data;
		if (down_interruptible(&d->sem))
			return -ERESTARTSYS;
		len += sprintf(buf+len,"\nDevice %i: qset %i, q %i, sz %li\n",
				i, d->qset, d->quantum, d->size);
		for (; qs && len <= limit; qs = qs->next) { /* scan the list */
			len += sprintf(buf + len, "  item at %p, qset at %p\n",
					qs, qs->data);
			if (qs->data && !qs->next) /* dump only the last item */
				for (j = 0; j < d->qset; j++) {
					if (qs->data[j])
						len += sprintf(buf + len,
								"    % 4i: %8p\n",
								j, qs->data[j]);
				}
		}
		up(&scull_devices[i].sem);
	}
	*eof = 1;
	return len;
}


/*
 * For now, the seq_file implementation will exist in parallel.  The
 * older read_procmem function should maybe go away, though.
 */

/*
 * Here are our sequence iteration methods.  Our "position" is
 * simply the device number.
 */
static void *scull_seq_start(struct seq_file *s, loff_t *pos)
{
	if (*pos >= scull_nr_devs)
		return NULL;   /* No more to read */
	return scull_devices + *pos;
}

static void *scull_seq_next(struct seq_file *s, void *v, loff_t *pos)
{
	(*pos)++;
	if (*pos >= scull_nr_devs)
		return NULL;
	return scull_devices + *pos;
}

static void scull_seq_stop(struct seq_file *s, void *v)
{
	/* Actually, there's nothing to do here */
}

static int scull_seq_show(struct seq_file *s, void *v)
{
	struct scull_dev *dev = (struct scull_dev *) v;
	struct scull_qset *d;
	int i;

	if (down_interruptible(&dev->sem))
		return -ERESTARTSYS;
	seq_printf(s, "\nDevice %i: qset %i, q %i, sz %li\n",
			(int) (dev - scull_devices), dev->qset,
			dev->quantum, dev->size);
	for (d = dev->data; d; d = d->next) { /* scan the list */
		seq_printf(s, "  item at %p, qset at %p\n", d, d->data);
		if (d->data && !d->next) /* dump only the last item */
			for (i = 0; i < dev->qset; i++) {
				if (d->data[i])
					seq_printf(s, "    % 4i: %8p\n",
							i, d->data[i]);
			}
	}
	up(&dev->sem);
	return 0;
}
	
/*
 * Tie the sequence operators up.
 */
static struct seq_operations scull_seq_ops = {
	.start = scull_seq_start,
	.next  = scull_seq_next,
	.stop  = scull_seq_stop,
	.show  = scull_seq_show
};

/*
 * Now to implement the /proc file we need only make an open
 * method which sets up the sequence operators.
 */
static int scull_proc_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &scull_seq_ops);
}

/*
 * Create a set of file operations for our proc file.
 */
static struct file_operations scull_proc_ops = {
	.owner   = THIS_MODULE,
	.open    = scull_proc_open,
	.read    = seq_read,
	.llseek  = seq_lseek,
	.release = seq_release
};
	

/*
 * Actually create (and remove) the /proc file(s).
 */

static void scull_create_proc(void)
{
	struct proc_dir_entry *entry;
	create_proc_read_entry("scullmem", 0 /* default mode */,
			NULL /* parent dir */, scull_read_procmem,
			NULL /* client data */);
	entry = create_proc_entry("scullseq", 0, NULL);
	if (entry)
		entry->proc_fops = &scull_proc_ops;
}

static void scull_remove_proc(void)
{
	/* no problem if it was not registered */
	remove_proc_entry("scullmem", NULL /* parent dir */);
	remove_proc_entry("scullseq", NULL);
}


#endif /* SCULL_DEBUG */





/*
 * Open and close
 */

int scull_open(struct inode *inode, struct file *filp)
{
	struct scull_dev *dev; /* device information */

	dev = container_of(inode->i_cdev, struct scull_dev, cdev);
	filp->private_data = dev; /* for other methods */

	/* 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;
		scull_trim(dev); /* ignore errors */
		up(&dev->sem);
	}
	return 0;          /* success */
}

int scull_release(struct inode *inode, struct file *filp)
{
	return 0;
}
/*
 * Follow the list
 */
struct scull_qset *scull_follow(struct scull_dev *dev, int n)
{
	struct scull_qset *qs = dev->data;

        /* Allocate first qset explicitly if need be */
	if (! qs) {
		qs = dev->data = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);
		if (qs == NULL)
			return NULL;  /* Never mind */
		memset(qs, 0, sizeof(struct scull_qset));
	}

	/* Then follow the list */
	while (n--) {
		if (!qs->next) {
			qs->next = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);
			if (qs->next == NULL)
				return NULL;  /* Never mind */
			memset(qs->next, 0, sizeof(struct scull_qset));
		}
		qs = qs->next;
		continue;
	}
	return qs;
}

/*
 * Data management: read and write
 */

ssize_t scull_read(struct file *filp, char __user *buf, size_t count,
                loff_t *f_pos)
{
	struct scull_dev *dev = filp->private_data; 
	struct scull_qset *dptr;	/* the first listitem */
	int quantum = dev->quantum, 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 out;
	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 = scull_follow(dev, item);

	if (dptr == NULL || !dptr->data || ! dptr->data[s_pos])
		goto out; /* don't fill holes */

	/* read only up to the end of this quantum */
	if (count > quantum - q_pos)
		count = quantum - q_pos;

	if (copy_to_user(buf, dptr->data[s_pos] + q_pos, count)) {
		retval = -EFAULT;
		goto out;
	}
	*f_pos += count;
	retval = count;

  out:
	up(&dev->sem);
	return retval;
}

ssize_t scull_write(struct file *filp, const char __user *buf, size_t count,
                loff_t *f_pos)