USe interruptible version of down.

[cascardo/kernel/samples/char2/.git] / hellochar.c

diff --git a/hellochar.c b/hellochar.c
index 9d4e40a..628f53c 100644 (file)
--- a/hellochar.c
+++ b/hellochar.c
@@ -20,29 +20,99 @@
 #include <linux/fs.h>
 #include <linux/cdev.h>
 #include <linux/slab.h>
+#include <linux/semaphore.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";
+
+struct hello_buffer {
+       size_t len;
+       char buffer[0];
+};
+static struct hello_buffer *hello;
+static DECLARE_MUTEX(hello_mtx);
 
 static int hello_open(struct inode *ino, struct file *fp)
 {
-       printk(KERN_DEBUG "Hello, World!\n");
+       if (down_interruptible(&hello_mtx))
+               return -ERESTARTSYS;
+       if (fp->f_flags & O_TRUNC) {
+               memset(hello->buffer, 0, MAXLEN);
+               hello->len = 0;
+       }
+       if (fp->f_flags & O_APPEND)
+               fp->f_pos = hello->len;
+       up(&hello_mtx);
+       return 0;
+}
+
+static ssize_t hello_read(struct file *fp, char __user *buf, size_t sz,
+       loff_t *pos)
+{
+       int r;
+       if (down_interruptible(&hello_mtx))
+               return -ERESTARTSYS;
+       if (sz + *pos > hello->len)
+               sz = hello->len - *pos;
+       r = copy_to_user(buf, hello->buffer + *pos, sz);
+       up(&hello_mtx);
+       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)
+{
+       int r;
+       if (down_interruptible(&hello_mtx))
+               return -ERESTARTSYS;
+       if (sz + *pos > MAXLEN)
+               sz = MAXLEN - *pos;
+       r = copy_from_user(hello->buffer + *pos, buf, sz);
+       if (r) {
+               up(&hello_mtx);
+               return -EFAULT;
+       }
+       *pos += sz;
+       if (hello->len < *pos)
+               hello->len = *pos;
+       up(&hello_mtx);
+       return sz;
+}
+
+static int hello_release(struct inode *ino, struct file *fp)
+{
        return 0;
 }
 
 static const struct file_operations hello_fops = {
        .owner = THIS_MODULE,
        .open = hello_open,
+       .release = hello_release,
+       .read = hello_read,
+       .write = hello_write,
 };
 
 static int __init ch_init(void)
 {
        int r = 0;
+       hello = kzalloc(sizeof(*hello) + MAXLEN, GFP_KERNEL);
+       if (!hello) {
+               r = -ENOMEM;
+               goto out;
+       }
+       memcpy(hello->buffer, default_greeting, sizeof(default_greeting));
+       hello->len = sizeof(default_greeting);
        r = alloc_chrdev_region(&devnum, 0, 256, "hello");
        if (r)
-               goto out;
+               goto reg_out;
        dev = cdev_alloc();
        if (!dev) {
                r = -ENOMEM;
@@ -58,6 +128,8 @@ add_out:
        kfree(dev);
 cdev_out:
        unregister_chrdev_region(devnum, 256);
+reg_out:
+       kfree(hello);
 out:
        return r;
 }
@@ -66,6 +138,7 @@ static void __exit ch_exit(void)
 {
        cdev_del(dev);
        unregister_chrdev_region(devnum, 256);
+       kfree(hello);
 }
 
 module_init(ch_init);