Linux Device Drivers 3 examples

1 files changed, 673 insertions, 0 deletions

diff --git a/scull/main.c b/scull/main.c
new file mode 100644
index 0000000..b1d9e3a
--- /dev/null
+++ b/scull/main.c
@@ -0,0 +1,673 @@
+/*
+ * 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)
+{
+	struct scull_dev *dev = filp->private_data;
+	struct scull_qset *dptr;
+	int quantum = dev->quantum, qset = dev->qset;
+	int itemsize = quantum * qset;
+	int item, s_pos, q_pos, rest;
+	ssize_t retval = -ENOMEM; /* value used in "goto out" statements */
+
+	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 = scull_follow(dev, item);
+	if (dptr == NULL)
+		goto out;
+	if (!dptr->data) {
+		dptr->data = kmalloc(qset * sizeof(char *), GFP_KERNEL);
+		if (!dptr->data)
+			goto out;
+		memset(dptr->data, 0, qset * sizeof(char *));
+	}
+	if (!dptr->data[s_pos]) {
+		dptr->data[s_pos] = kmalloc(quantum, GFP_KERNEL);
+		if (!dptr->data[s_pos])
+			goto out;
+	}
+	/* write only up to the end of this quantum */
+	if (count > quantum - q_pos)
+		count = quantum - q_pos;
+
+	if (copy_from_user(dptr->data[s_pos]+q_pos, buf, count)) {
+		retval = -EFAULT;
+		goto out;
+	}
+	*f_pos += count;
+	retval = count;
+
+        /* update the size */
+	if (dev->size < *f_pos)
+		dev->size = *f_pos;
+
+  out:
+	up(&dev->sem);
+	return retval;
+}
+
+/*
+ * The ioctl() implementation
+ */
+
+int scull_ioctl(struct inode *inode, struct file *filp,
+                 unsigned int cmd, unsigned long arg)
+{
+
+	int err = 0, tmp;
+	int retval = 0;
+    
+	/*
+	 * extract the type and number bitfields, and don't decode
+	 * wrong cmds: return ENOTTY (inappropriate ioctl) before access_ok()
+	 */
+	if (_IOC_TYPE(cmd) != SCULL_IOC_MAGIC) return -ENOTTY;
+	if (_IOC_NR(cmd) > SCULL_IOC_MAXNR) return -ENOTTY;
+
+	/*
+	 * the direction is a bitmask, and VERIFY_WRITE catches R/W
+	 * transfers. `Type' is user-oriented, while
+	 * access_ok 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 SCULL_IOCRESET:
+		scull_quantum = SCULL_QUANTUM;
+		scull_qset = SCULL_QSET;
+		break;
+        
+	  case SCULL_IOCSQUANTUM: /* Set: arg points to the value */
+		if (! capable (CAP_SYS_ADMIN))
+			return -EPERM;
+		retval = __get_user(scull_quantum, (int __user *)arg);
+		break;
+
+	  case SCULL_IOCTQUANTUM: /* Tell: arg is the value */
+		if (! capable (CAP_SYS_ADMIN))
+			return -EPERM;
+		scull_quantum = arg;
+		break;
+
+	  case SCULL_IOCGQUANTUM: /* Get: arg is pointer to result */
+		retval = __put_user(scull_quantum, (int __user *)arg);
+		break;
+
+	  case SCULL_IOCQQUANTUM: /* Query: return it (it's positive) */
+		return scull_quantum;
+
+	  case SCULL_IOCXQUANTUM: /* eXchange: use arg as pointer */
+		if (! capable (CAP_SYS_ADMIN))
+			return -EPERM;
+		tmp = scull_quantum;
+		retval = __get_user(scull_quantum, (int __user *)arg);
+		if (retval == 0)
+			retval = __put_user(tmp, (int __user *)arg);
+		break;
+
+	  case SCULL_IOCHQUANTUM: /* sHift: like Tell + Query */
+		if (! capable (CAP_SYS_ADMIN))
+			return -EPERM;
+		tmp = scull_quantum;
+		scull_quantum = arg;
+		return tmp;
+        
+	  case SCULL_IOCSQSET:
+		if (! capable (CAP_SYS_ADMIN))
+			return -EPERM;
+		retval = __get_user(scull_qset, (int __user *)arg);
+		break;
+
+	  case SCULL_IOCTQSET:
+		if (! capable (CAP_SYS_ADMIN))
+			return -EPERM;
+		scull_qset = arg;
+		break;
+
+	  case SCULL_IOCGQSET:
+		retval = __put_user(scull_qset, (int __user *)arg);
+		break;
+
+	  case SCULL_IOCQQSET:
+		return scull_qset;
+
+	  case SCULL_IOCXQSET:
+		if (! capable (CAP_SYS_ADMIN))
+			return -EPERM;
+		tmp = scull_qset;
+		retval = __get_user(scull_qset, (int __user *)arg);
+		if (retval == 0)
+			retval = put_user(tmp, (int __user *)arg);
+		break;
+
+	  case SCULL_IOCHQSET:
+		if (! capable (CAP_SYS_ADMIN))
+			return -EPERM;
+		tmp = scull_qset;
+		scull_qset = arg;
+		return tmp;
+
+        /*
+         * The following two change the buffer size for scullpipe.
+         * The scullpipe device uses this same ioctl method, just to
+         * write less code. Actually, it's the same driver, isn't it?
+         */
+
+	  case SCULL_P_IOCTSIZE:
+		scull_p_buffer = arg;
+		break;
+
+	  case SCULL_P_IOCQSIZE:
+		return scull_p_buffer;
+
+
+	  default:  /* redundant, as cmd was checked against MAXNR */
+		return -ENOTTY;
+	}
+	return retval;
+
+}
+
+
+
+/*
+ * The "extended" operations -- only seek
+ */
+
+loff_t scull_llseek(struct file *filp, loff_t off, int whence)
+{
+	struct scull_dev *dev = filp->private_data;
+	loff_t 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;
+}
+
+
+
+struct file_operations scull_fops = {
+	.owner =    THIS_MODULE,
+	.llseek =   scull_llseek,
+	.read =     scull_read,
+	.write =    scull_write,
+	.ioctl =    scull_ioctl,
+	.open =     scull_open,
+	.release =  scull_release,
+};
+
+/*
+ * Finally, the module stuff
+ */
+
+/*
+ * The cleanup function is used to handle initialization failures as well.
+ * Thefore, it must be careful to work correctly even if some of the items
+ * have not been initialized
+ */
+void scull_cleanup_module(void)
+{
+	int i;
+	dev_t devno = MKDEV(scull_major, scull_minor);
+
+	/* Get rid of our char dev entries */
+	if (scull_devices) {
+		for (i = 0; i < scull_nr_devs; i++) {
+			scull_trim(scull_devices + i);
+			cdev_del(&scull_devices[i].cdev);
+		}
+		kfree(scull_devices);
+	}
+
+#ifdef SCULL_DEBUG /* use proc only if debugging */
+	scull_remove_proc();
+#endif
+
+	/* cleanup_module is never called if registering failed */
+	unregister_chrdev_region(devno, scull_nr_devs);
+
+	/* and call the cleanup functions for friend devices */
+	scull_p_cleanup();
+	scull_access_cleanup();
+
+}
+
+
+/*
+ * Set up the char_dev structure for this device.
+ */
+static void scull_setup_cdev(struct scull_dev *dev, int index)
+{
+	int err, devno = MKDEV(scull_major, scull_minor + index);
+    
+	cdev_init(&dev->cdev, &scull_fops);
+	dev->cdev.owner = THIS_MODULE;
+	dev->cdev.ops = &scull_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);
+}
+
+
+int scull_init_module(void)
+{
+	int result, i;
+	dev_t dev = 0;
+
+/*
+ * Get a range of minor numbers to work with, asking for a dynamic
+ * major unless directed otherwise at load time.
+ */
+	if (scull_major) {
+		dev = MKDEV(scull_major, scull_minor);
+		result = register_chrdev_region(dev, scull_nr_devs, "scull");
+	} else {
+		result = alloc_chrdev_region(&dev, scull_minor, scull_nr_devs,
+				"scull");
+		scull_major = MAJOR(dev);
+	}
+	if (result < 0) {
+		printk(KERN_WARNING "scull: can't get major %d\n", scull_major);
+		return result;
+	}
+
+        /* 
+	 * allocate the devices -- we can't have them static, as the number
+	 * can be specified at load time
+	 */
+	scull_devices = kmalloc(scull_nr_devs * sizeof(struct scull_dev), GFP_KERNEL);
+	if (!scull_devices) {
+		result = -ENOMEM;
+		goto fail;  /* Make this more graceful */
+	}
+	memset(scull_devices, 0, scull_nr_devs * sizeof(struct scull_dev));
+
+        /* Initialize each device. */
+	for (i = 0; i < scull_nr_devs; i++) {
+		scull_devices[i].quantum = scull_quantum;
+		scull_devices[i].qset = scull_qset;
+		init_MUTEX(&scull_devices[i].sem);
+		scull_setup_cdev(&scull_devices[i], i);
+	}
+
+        /* At this point call the init function for any friend device */
+	dev = MKDEV(scull_major, scull_minor + scull_nr_devs);
+	dev += scull_p_init(dev);
+	dev += scull_access_init(dev);
+
+#ifdef SCULL_DEBUG /* only when debugging */
+	scull_create_proc();
+#endif
+
+	return 0; /* succeed */
+
+  fail:
+	scull_cleanup_module();
+	return result;
+}
+
+module_init(scull_init_module);
+module_exit(scull_cleanup_module);