1 files changed, 105 insertions, 0 deletions
diff --git a/handlers/chardev.c b/handlers/chardev.c
new file mode 100644
index 0000000..3594bce
--- /dev/null
+++ b/handlers/chardev.c
@@ -0,0 +1,105 @@
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <asm/uaccess.h>
+
+#include "chardev.h"
+
+#define SUCCESS		0
+#define DEVICE_NAME	"chardev"
+#define BUF_LEN		80
+
+static int Major;
+static int opened = 0;
+static char msg[BUF_LEN];
+static char* msg_ptr;
+
+static struct file_operations fops = {
+	.read = device_read,
+	.write = device_write,
+	.open = device_open,
+	.release = device_release
+};
+
+int init_module(void)
+{
+	Major = register_chrdev(0, DEVICE_NAME, &fops);
+
+	if (Major < 0) {
+		printk(KERN_ALERT "Registering char device failed with %d\n", Major);
+		return Major;
+	}
+
+	printk(KERN_INFO "I was assigned major number %d. To talk to\n", Major);
+	printk(KERN_INFO "the driver, create a dev file with\n");
+	printk(KERN_INFO "'mknod /dev/%s c %d 0'.\n", DEVICE_NAME, Major);
+	printk(KERN_INFO "Try to cat and echo to the device file.\n");
+	printk(KERN_INFO "Remove the device file and module when done.\n");
+
+	return SUCCESS;
+}
+
+void cleanup_module(void)
+{
+	unregister_chrdev(Major, DEVICE_NAME);
+}
+
+static int device_open(struct inode* inode, struct file* filp)
+{
+	static int counter = 0;
+
+	if (opened)
+		return -EBUSY;
+
+	opened++;
+	if (counter++ == 0)
+		sprintf(msg, "Come on, write something here :D\n");
+
+	msg_ptr = msg;
+	try_module_get(THIS_MODULE);
+
+	return SUCCESS;
+}
+
+static int device_release(struct inode* inode, struct file* filp)
+{
+	opened--;
+
+	module_put(THIS_MODULE);
+
+	return 0;
+}
+
+static ssize_t device_read(struct file* filp, char* buffer, size_t len, loff_t* off)
+{
+	int bytes = 0;
+
+	if (*msg_ptr == 0)
+		return 0;
+
+	while (len-- && *msg_ptr) {
+		put_user(*msg_ptr++, buffer++);
+		bytes++;
+	}
+
+	return bytes;
+}
+
+static ssize_t device_write(struct file* filp, const char* buff, size_t len, loff_t* off)
+{
+	int bytes = 0;
+
+	if (len > BUF_LEN) {
+		printk(KERN_ALERT "Error: dude you tried to overflow my buffer!\n");
+		return -ENOBUFS;
+	}
+
+	while (len--) {
+		get_user(msg[bytes], buff++);
+		bytes++;
+	}
+	msg[bytes] = '\0';
+
+	msg_ptr = msg;
+	return bytes;
+}