add kobjectexample

Signed-off-by: Wenchao Hao <haowenchao@huawei.com>

Makefile

@@ -2,6 +2,7 @@ KDIR=/usr/src/kernels/$(shell uname -r)
 
 obj-m += demo.o
 obj-m += blk_kprobe.o
+obj-m += kobject-example.o
 
 all:
 	make -C $(KDIR) M=$(shell pwd) modules

kobject-example.c

@@ -0,0 +1,101 @@
+#include <linux/kobject.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/module.h>
+#include <linux/init.h>
+
+static int foo;
+static int baz;
+static int bar;
+
+static ssize_t foo_show(struct kobject *kobj, struct kobj_attribute *attr,
+			char *buf)
+{
+	return sysfs_emit(buf, "%d\n", foo);
+}
+
+static ssize_t foo_store(struct kobject *kobj, struct kobj_attribute *attr,
+			 const char *buf, size_t count)
+{
+	int ret;
+
+	ret = kstrtoint(buf, 10, &foo);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static struct kobj_attribute foo_attribute =
+	__ATTR(foo, 0664, foo_show, foo_store);
+
+static ssize_t b_show(struct kobject *kobj, struct kobj_attribute *attr,
+		      char *buf)
+{
+	int var;
+
+	if (strcmp(attr->attr.name, "baz") == 0)
+		var = baz;
+	else
+		var = bar;
+	return sysfs_emit(buf, "%d\n", var);
+}
+
+static ssize_t b_store(struct kobject *kobj, struct kobj_attribute *attr,
+		       const char *buf, size_t count)
+{
+	int var, ret;
+
+	ret = kstrtoint(buf, 10, &var);
+	if (ret < 0)
+		return ret;
+
+	if (strcmp(attr->attr.name, "baz") == 0)
+		baz = var;
+	else
+		bar = var;
+	return count;
+}
+
+static struct kobj_attribute baz_attribute =
+	__ATTR(baz, 0664, b_show, b_store);
+static struct kobj_attribute bar_attribute =
+	__ATTR(bar, 0664, b_show, b_store);
+
+static struct attribute *attrs[] = {
+	&foo_attribute.attr,
+	&baz_attribute.attr,
+	&bar_attribute.attr,
+	NULL,	/* need to NULL terminate the list of attributes */
+};
+
+static struct attribute_group attr_group = {
+	.attrs = attrs,
+};
+
+static struct kobject *example_kobj;
+
+static int __init example_init(void)
+{
+	int retval;
+
+	example_kobj = kobject_create_and_add("kobject_example", kernel_kobj);
+	if (!example_kobj)
+		return -ENOMEM;
+
+	retval = sysfs_create_group(example_kobj, &attr_group);
+	if (retval)
+		kobject_put(example_kobj);
+
+	return retval;
+}
+
+static void __exit example_exit(void)
+{
+	kobject_put(example_kobj);
+}
+
+module_init(example_init);
+module_exit(example_exit);
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");