Linux Device Drivers 3 examples

1 files changed, 632 insertions, 0 deletions

diff --git a/sculld/main.c b/sculld/main.c
new file mode 100644
index 0000000..a4854a5
--- /dev/null
+++ b/sculld/main.c
@@ -0,0 +1,632 @@
+/* -*- C -*-
+ * main.c -- the bare sculld 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 "sculld.h"		/* local definitions */
+
+
+int sculld_major =   SCULLD_MAJOR;
+int sculld_devs =    SCULLD_DEVS;	/* number of bare sculld devices */
+int sculld_qset =    SCULLD_QSET;
+int sculld_order =   SCULLD_ORDER;
+
+module_param(sculld_major, int, 0);
+module_param(sculld_devs, int, 0);
+module_param(sculld_qset, int, 0);
+module_param(sculld_order, int, 0);
+MODULE_AUTHOR("Alessandro Rubini");
+MODULE_LICENSE("Dual BSD/GPL");
+
+struct sculld_dev *sculld_devices; /* allocated in sculld_init */
+
+int sculld_trim(struct sculld_dev *dev);
+void sculld_cleanup(void);
+
+
+
+/* Device model stuff */
+
+static struct ldd_driver sculld_driver = {
+	.version = "$Revision: 1.21 $",
+	.module = THIS_MODULE,
+	.driver = {
+		.name = "sculld",
+	},
+};
+
+
+
+#ifdef SCULLD_USE_PROC /* don't waste space if unused */
+/*
+ * The proc filesystem: function to read and entry
+ */
+
+void sculld_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 sculld_read_procmem(char *buf, char **start, off_t offset,
+                   int count, int *eof, void *data)
+{
+	int i, j, order, qset, len = 0;
+	int limit = count - 80; /* Don't print more than this */
+	struct sculld_dev *d;
+
+	*start = buf;
+	for(i = 0; i < sculld_devs; i++) {
+		d = &sculld_devices[i];
+		if (down_interruptible (&d->sem))
+			return -ERESTARTSYS;
+		qset = d->qset;  /* retrieve the features of each device */
+		order = d->order;
+		len += sprintf(buf+len,"\nDevice %i: qset %i, order %i, sz %li\n",
+				i, qset, order, (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);
+			sculld_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]);
+					sculld_proc_offset (buf, start, &offset, &len);
+					if (len > limit)
+						goto out;
+				}
+		}
+	  out:
+		up (&sculld_devices[i].sem);
+		if (len > limit)
+			break;
+	}
+	*eof = 1;
+	return len;
+}
+
+#endif /* SCULLD_USE_PROC */
+
+/*
+ * Open and close
+ */
+
+int sculld_open (struct inode *inode, struct file *filp)
+{
+	struct sculld_dev *dev; /* device information */
+
+	/*  Find the device */
+	dev = container_of(inode->i_cdev, struct sculld_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;
+		sculld_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 sculld_release (struct inode *inode, struct file *filp)
+{
+	return 0;
+}
+
+/*
+ * Follow the list 
+ */
+struct sculld_dev *sculld_follow(struct sculld_dev *dev, int n)
+{
+	while (n--) {
+		if (!dev->next) {
+			dev->next = kmalloc(sizeof(struct sculld_dev), GFP_KERNEL);
+			memset(dev->next, 0, sizeof(struct sculld_dev));
+		}
+		dev = dev->next;
+		continue;
+	}
+	return dev;
+}
+
+/*
+ * Data management: read and write
+ */
+
+ssize_t sculld_read (struct file *filp, char __user *buf, size_t count,
+                loff_t *f_pos)
+{
+	struct sculld_dev *dev = filp->private_data; /* the first listitem */
+	struct sculld_dev *dptr;
+	int quantum = PAGE_SIZE << dev->order;
+	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 = sculld_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 sculld_write (struct file *filp, const char __user *buf, size_t count,
+                loff_t *f_pos)
+{
+	struct sculld_dev *dev = filp->private_data;
+	struct sculld_dev *dptr;
+	int quantum = PAGE_SIZE << dev->order;
+	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 = sculld_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 *));
+	}
+	/* Here's the allocation of a single quantum */
+	if (!dptr->data[s_pos]) {
+		dptr->data[s_pos] =
+			(void *)__get_free_pages(GFP_KERNEL, dptr->order);
+		if (!dptr->data[s_pos])
+			goto nomem;
+		memset(dptr->data[s_pos], 0, PAGE_SIZE << dptr->order);
+	}
+	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 sculld_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) != SCULLD_IOC_MAGIC) return -ENOTTY;
+	if (_IOC_NR(cmd) > SCULLD_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 SCULLD_IOCRESET:
+		sculld_qset = SCULLD_QSET;
+		sculld_order = SCULLD_ORDER;
+		break;
+
+	case SCULLD_IOCSORDER: /* Set: arg points to the value */
+		ret = __get_user(sculld_order, (int __user *) arg);
+		break;
+
+	case SCULLD_IOCTORDER: /* Tell: arg is the value */
+		sculld_order = arg;
+		break;
+
+	case SCULLD_IOCGORDER: /* Get: arg is pointer to result */
+		ret = __put_user (sculld_order, (int __user *) arg);
+		break;
+
+	case SCULLD_IOCQORDER: /* Query: return it (it's positive) */
+		return sculld_order;
+
+	case SCULLD_IOCXORDER: /* eXchange: use arg as pointer */
+		tmp = sculld_order;
+		ret = __get_user(sculld_order, (int __user *) arg);
+		if (ret == 0)
+			ret = __put_user(tmp, (int __user *) arg);
+		break;
+
+	case SCULLD_IOCHORDER: /* sHift: like Tell + Query */
+		tmp = sculld_order;
+		sculld_order = arg;
+		return tmp;
+
+	case SCULLD_IOCSQSET:
+		ret = __get_user(sculld_qset, (int __user *) arg);
+		break;
+
+	case SCULLD_IOCTQSET:
+		sculld_qset = arg;
+		break;
+
+	case SCULLD_IOCGQSET:
+		ret = __put_user(sculld_qset, (int __user *)arg);
+		break;
+
+	case SCULLD_IOCQQSET:
+		return sculld_qset;
+
+	case SCULLD_IOCXQSET:
+		tmp = sculld_qset;
+		ret = __get_user(sculld_qset, (int __user *)arg);
+		if (ret == 0)
+			ret = __put_user(tmp, (int __user *)arg);
+		break;
+
+	case SCULLD_IOCHQSET:
+		tmp = sculld_qset;
+		sculld_qset = arg;
+		return tmp;
+
+	default:  /* redundant, as cmd was checked against MAXNR */
+		return -ENOTTY;
+	}
+
+	return ret;
+}
+
+/*
+ * The "extended" operations
+ */
+
+loff_t sculld_llseek (struct file *filp, loff_t off, int whence)
+{
+	struct sculld_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 sculld_do_deferred_op(void *p)
+{
+	struct async_work *stuff = (struct async_work *) p;
+	aio_complete(stuff->iocb, stuff->result, 0);
+	kfree(stuff);
+}
+
+
+static int sculld_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 = sculld_write(iocb->ki_filp, buf, count, &pos);
+	else
+		result = sculld_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, sculld_do_deferred_op, stuff);
+	schedule_delayed_work(&stuff->work, HZ/100);
+	return -EIOCBQUEUED;
+}
+
+
+static ssize_t sculld_aio_read(struct kiocb *iocb, char __user *buf, size_t count,
+		loff_t pos)
+{
+	return sculld_defer_op(0, iocb, buf, count, pos);
+}
+
+static ssize_t sculld_aio_write(struct kiocb *iocb, const char __user *buf,
+		size_t count, loff_t pos)
+{
+	return sculld_defer_op(1, iocb, (char __user *) buf, count, pos);
+}
+
+
+ 
+/*
+ * Mmap *is* available, but confined in a different file
+ */
+extern int sculld_mmap(struct file *filp, struct vm_area_struct *vma);
+
+
+/*
+ * The fops
+ */
+
+struct file_operations sculld_fops = {
+	.owner =     THIS_MODULE,
+	.llseek =    sculld_llseek,
+	.read =	     sculld_read,
+	.write =     sculld_write,
+	.ioctl =     sculld_ioctl,
+	.mmap =	     sculld_mmap,
+	.open =	     sculld_open,
+	.release =   sculld_release,
+	.aio_read =  sculld_aio_read,
+	.aio_write = sculld_aio_write,
+};
+
+int sculld_trim(struct sculld_dev *dev)
+{
+	struct sculld_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) {
+			/* This code frees a whole quantum-set */
+			for (i = 0; i < qset; i++)
+				if (dptr->data[i])
+					free_pages((unsigned long)(dptr->data[i]),
+							dptr->order);
+
+			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 = sculld_qset;
+	dev->order = sculld_order;
+	dev->next = NULL;
+	return 0;
+}
+
+
+static void sculld_setup_cdev(struct sculld_dev *dev, int index)
+{
+	int err, devno = MKDEV(sculld_major, index);
+    
+	cdev_init(&dev->cdev, &sculld_fops);
+	dev->cdev.owner = THIS_MODULE;
+	dev->cdev.ops = &sculld_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);
+}
+
+static ssize_t sculld_show_dev(struct device *ddev, char *buf)
+{
+	struct sculld_dev *dev = ddev->driver_data;
+
+	return print_dev_t(buf, dev->cdev.dev);
+}
+
+static DEVICE_ATTR(dev, S_IRUGO, sculld_show_dev, NULL);
+
+static void sculld_register_dev(struct sculld_dev *dev, int index)
+{
+	sprintf(dev->devname, "sculld%d", index);
+	dev->ldev.name = dev->devname;
+	dev->ldev.driver = &sculld_driver;
+	dev->ldev.dev.driver_data = dev;
+	register_ldd_device(&dev->ldev);
+	device_create_file(&dev->ldev.dev, &dev_attr_dev);
+}
+
+
+/*
+ * Finally, the module stuff
+ */
+
+int sculld_init(void)
+{
+	int result, i;
+	dev_t dev = MKDEV(sculld_major, 0);
+	
+	/*
+	 * Register your major, and accept a dynamic number.
+	 */
+	if (sculld_major)
+		result = register_chrdev_region(dev, sculld_devs, "sculld");
+	else {
+		result = alloc_chrdev_region(&dev, 0, sculld_devs, "sculld");
+		sculld_major = MAJOR(dev);
+	}
+	if (result < 0)
+		return result;
+
+	/*
+	 * Register with the driver core.
+	 */
+	register_ldd_driver(&sculld_driver);
+	
+	/* 
+	 * allocate the devices -- we can't have them static, as the number
+	 * can be specified at load time
+	 */
+	sculld_devices = kmalloc(sculld_devs*sizeof (struct sculld_dev), GFP_KERNEL);
+	if (!sculld_devices) {
+		result = -ENOMEM;
+		goto fail_malloc;
+	}
+	memset(sculld_devices, 0, sculld_devs*sizeof (struct sculld_dev));
+	for (i = 0; i < sculld_devs; i++) {
+		sculld_devices[i].order = sculld_order;
+		sculld_devices[i].qset = sculld_qset;
+		sema_init (&sculld_devices[i].sem, 1);
+		sculld_setup_cdev(sculld_devices + i, i);
+		sculld_register_dev(sculld_devices + i, i);
+	}
+
+
+#ifdef SCULLD_USE_PROC /* only when available */
+	create_proc_read_entry("sculldmem", 0, NULL, sculld_read_procmem, NULL);
+#endif
+	return 0; /* succeed */
+
+  fail_malloc:
+	unregister_chrdev_region(dev, sculld_devs);
+	return result;
+}
+
+
+
+void sculld_cleanup(void)
+{
+	int i;
+
+#ifdef SCULLD_USE_PROC
+	remove_proc_entry("sculldmem", NULL);
+#endif
+
+	for (i = 0; i < sculld_devs; i++) {
+		unregister_ldd_device(&sculld_devices[i].ldev);
+		cdev_del(&sculld_devices[i].cdev);
+		sculld_trim(sculld_devices + i);
+	}
+	kfree(sculld_devices);
+	unregister_ldd_driver(&sculld_driver);
+	unregister_chrdev_region(MKDEV (sculld_major, 0), sculld_devs);
+}
+
+
+module_init(sculld_init);
+module_exit(sculld_cleanup);