Added len attribute.

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

diff --git a/hellochar.c b/hellochar.c
index 576968b..940bfeb 100644 (file)
--- a/hellochar.c
+++ b/hellochar.c
@@ -18,23 +18,181 @@
 
 #include <linux/module.h>
 #include <linux/fs.h>
+#include <linux/cdev.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+#include <asm/uaccess.h>
+#include <linux/circ_buf.h>
+#include <linux/sched.h>
+#include <linux/completion.h>
+#include <linux/device.h>
 
 MODULE_LICENSE("GPL");
-static int major = 10;
-module_param_named(major, major, int, S_IRUGO | S_IWUSR);
 
-static int __init ch_init(void)
+#define MAXLEN 4096
+static dev_t devnum;
+static struct cdev *dev;
+static const char default_greeting[] = "Hello, World!\n";
+
+static struct circ_buf *hello;
+static struct circ_buf hello_instance;
+static DEFINE_MUTEX(hello_mtx);
+static DECLARE_COMPLETION(hello_wait);
+
+static int hello_open(struct inode *ino, struct file *fp)
+{
+       return 0;
+}
+
+static ssize_t hello_read(struct file *fp, char __user *buf, size_t sz,
+       loff_t *pos)
 {
        int r;
-       r = register_chrdev_region(MKDEV(major, 0), 256, "hello");
+       size_t fsz;
+       size_t ssz;
+       size_t len;
+       if (mutex_lock_interruptible(&hello_mtx))
+               return -ERESTARTSYS;
+       len = CIRC_CNT(hello->head, hello->tail, MAXLEN);
+       if (sz > len)
+               sz = len;
+       /* First, copy at most until the limit of the buffer */
+       fsz = min(sz, CIRC_CNT_TO_END(hello->head, hello->tail, MAXLEN));
+       r = copy_to_user(buf, hello->buf + hello->tail, fsz);
+       ssz = sz - fsz;
+       if (!r && !ssz)
+               r = copy_to_user(buf + fsz, hello->buf, ssz);
+       if (!r)
+               hello->tail = (hello->tail + sz) & ~MAXLEN;
+       mutex_unlock(&hello_mtx);
+       if (r)
+               return -EFAULT;
+       complete(&hello_wait);
+       return sz;
+}
+
+static ssize_t hello_write(struct file *fp, const char __user *buf, size_t sz,
+       loff_t *pos)
+{
+       int r;
+       size_t fsz;
+       size_t ssz;
+       size_t len;
+       if (mutex_lock_interruptible(&hello_mtx))
+               return -ERESTARTSYS;
+       len = CIRC_SPACE(hello->head, hello->tail, MAXLEN);
+       while (len == 0) {
+               mutex_unlock(&hello_mtx);
+               if (wait_for_completion_interruptible(&hello_wait))
+                       return -ERESTARTSYS;
+               if (mutex_lock_interruptible(&hello_mtx))
+                       return -ERESTARTSYS;
+               len = CIRC_SPACE(hello->head, hello->tail, MAXLEN);
+       }
+       if (sz > len)
+               sz = len;
+       fsz = min(sz, CIRC_SPACE_TO_END(hello->head, hello->tail, MAXLEN));
+       r = copy_from_user(hello->buf + hello->head, buf, fsz);
+       ssz = sz - fsz;
+       if (!r && !ssz)
+               r = copy_from_user(hello->buf, buf + fsz, ssz);
+       if (!r)
+               hello->head = (hello->head + sz) & ~MAXLEN;
+       mutex_unlock(&hello_mtx);
+       if (r)
+               return -EFAULT;
+       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 ssize_t hello_len_show(struct device *dev, struct device_attribute *attr,
+       char *buffer)
+{
+       size_t len = CIRC_CNT(hello->head, hello->tail, MAXLEN);
+       return sprintf(buffer, "%d\n", len);
+}
+
+static const struct device_attribute hello_len_attr = {
+       .attr = { .name = "len", .mode = 0444, },
+       .show = hello_len_show,
+};
+
+static struct class *hello_class;
+static struct device *hello_dev;
+
+static int __init ch_init(void)
+{
+       int r = 0;
+       hello = &hello_instance;
+       hello->buf = kzalloc(sizeof(*hello) + MAXLEN, GFP_KERNEL);
+       if (!hello) {
+               r = -ENOMEM;
+               goto out;
+       }
+       hello_class = class_create(THIS_MODULE, "hello");
+       if (IS_ERR(hello_class)) {
+               r = PTR_ERR(hello_class);
+               goto class_out;
+       }
+       memcpy(hello->buf, default_greeting, sizeof(default_greeting));
+       hello->head = sizeof(default_greeting);
+       r = alloc_chrdev_region(&devnum, 0, 256, "hello");
+       if (r)
+               goto reg_out;
+       hello_dev = device_create(hello_class, NULL, devnum, NULL, "hello");
+       if (!hello_dev) {
+               r = -ENODEV;
+               goto dev_out;
+       }
+       r = device_create_file(hello_dev, &hello_len_attr);
+       if (r)
+               goto file_out;
+       dev = cdev_alloc();
+       if (!dev) {
+               r = -ENOMEM;
+               goto cdev_out;
+       }
+       dev->ops = &hello_fops;
+       r = cdev_add(dev, devnum, 256);
        if (r)
-               return r;
+               goto add_out;
        return 0;
+add_out:
+       kfree(dev);
+cdev_out:
+       device_remove_file(hello_dev, &hello_len_attr);
+file_out:
+       device_destroy(hello_class, devnum);
+dev_out:
+       unregister_chrdev_region(devnum, 256);
+reg_out:
+       class_destroy(hello_class);
+class_out:
+       kfree(hello);
+out:
+       return r;
 }
 
 static void __exit ch_exit(void)
 {
-       unregister_chrdev_region(MKDEV(major, 0), 256);
+       cdev_del(dev);
+       device_remove_file(hello_dev, &hello_len_attr);
+       device_destroy(hello_class, devnum);
+       unregister_chrdev_region(devnum, 256);
+       kfree(hello->buf);
+       class_destroy(hello_class);
 }
 
 module_init(ch_init);