#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
+#include <asm/uaccess.h>
MODULE_LICENSE("GPL");
+#define MAXLEN 4000
static dev_t devnum;
static struct cdev *dev;
static const char default_greeting[] = "Hello, World!\n";
static int hello_open(struct inode *ino, struct file *fp)
{
- struct hello_buffer *hello = kmalloc(sizeof(*hello) + 4000, GFP_KERNEL);
+ struct hello_buffer *hello = kzalloc(sizeof(*hello) + MAXLEN, GFP_KERNEL);
if (!hello)
return -ENOMEM;
- hello->private_data = hello;
+ memcpy(hello->buffer, default_greeting, sizeof(default_greeting));
+ hello->len = sizeof(default_greeting);
+ fp->private_data = hello;
return 0;
}
static ssize_t hello_read(struct file *fp, char __user *buf, size_t sz,
loff_t *pos)
{
- return 0;
+ struct hello_buffer *hello = fp->private_data;
+ int r;
+ if (sz + *pos > hello->len)
+ sz = hello->len - *pos;
+ r = copy_to_user(buf, hello->buffer + *pos, sz);
+ if (r)
+ return -EFAULT;
+ *pos += sz;
+ return sz;
+}
+
+static ssize_t hello_write(struct file *fp, const char __user *buf, size_t sz,
+ loff_t *pos)
+{
+ struct hello_buffer *hello = fp->private_data;
+ int r;
+ if (sz + *pos > MAXLEN)
+ sz = MAXLEN - *pos;
+ r = copy_from_user(hello->buffer + *pos, buf, sz);
+ if (r)
+ return -EFAULT;
+ *pos += sz;
+ if (hello->len < *pos)
+ hello->len = *pos;
+ return sz;
}
static int hello_release(struct inode *ino, struct file *fp)
.open = hello_open,
.release = hello_release,
.read = hello_read,
+ .write = hello_write,
};
static int __init ch_init(void)