From: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Date: Mon, 24 May 2010 13:15:06 +0000 (-0400)
Subject: Added len attribute.
X-Git-Url: http://git.cascardo.eti.br/?p=cascardo%2Fkernel%2Fsamples%2Fchar2%2F.git;a=commitdiff_plain;h=HEAD

Added len attribute.
---

diff --git a/hellochar.c b/hellochar.c
index e601e38..940bfeb 100644
--- a/hellochar.c
+++ b/hellochar.c
@@ -117,6 +117,18 @@ static const struct file_operations hello_fops = {
 	.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;
 
@@ -144,6 +156,9 @@ static int __init ch_init(void)
 		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;
@@ -157,6 +172,8 @@ static int __init ch_init(void)
 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);
@@ -171,6 +188,7 @@ out:
 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->buf);