#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 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)
{
mutex_unlock(&hello_mtx);
if (r)
return -EFAULT;
+ complete(&hello_wait);
return sz;
}
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));
.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;
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;
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)
{
cdev_del(dev);
+ device_remove_file(hello_dev, &hello_len_attr);
+ device_destroy(hello_class, devnum);
unregister_chrdev_region(devnum, 256);
- kfree(hello);
+ kfree(hello->buf);
+ class_destroy(hello_class);
}
module_init(ch_init);