/* * Sample kobject implementation * * Copyright (C) 2004-2007 Greg Kroah-Hartman <greg@kroah.com> * Copyright (C) 2007 Novell Inc. * * Released under the GPL version 2 only. * */#include <linux/kobject.h>#include <linux/string.h>#include <linux/sysfs.h>#include <linux/module.h>#include <linux/init.h> /* * This module shows how to create a simple subdirectory in sysfs called * /sys/kernel/kobject-example  In that directory, 3 files are created: * "foo", "baz", and "bar".  If an integer is written to these files, it can be * later read out of it. */ static int foo;static int baz;static int bar; /* * The "foo" file where a static variable is read from and written to. */static ssize_t foo_show(struct kobject *kobj, struct kobj_attribute *attr,			char *buf){	return sprintf(buf, "%d\n", foo);} static ssize_t foo_store(struct kobject *kobj, struct kobj_attribute *attr,			 const char *buf, size_t count){	sscanf(buf, "%du", &foo);	return count;} static struct kobj_attribute foo_attribute =	__ATTR(foo, 0666, foo_show, foo_store); /* * More complex function where we determine which varible is being accessed by * looking at the attribute for the "baz" and "bar" files. */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 sprintf(buf, "%d\n", var);} static ssize_t b_store(struct kobject *kobj, struct kobj_attribute *attr,		       const char *buf, size_t count){	int var; 	sscanf(buf, "%du", &var);	if (strcmp(attr->attr.name, "baz") == 0)		baz = var;	else		bar = var;	return count;} static struct kobj_attribute baz_attribute =	__ATTR(baz, 0666, b_show, b_store);static struct kobj_attribute bar_attribute =	__ATTR(bar, 0666, b_show, b_store);  /* * Create a group of attributes so that we can create and destory them all * at once. */static struct attribute *attrs[] = {	&foo_attribute.attr,	&baz_attribute.attr,	&bar_attribute.attr,	NULL,	/* need to NULL terminate the list of attributes */}; /* * An unnamed attribute group will put all of the attributes directly in * the kobject directory.  If we specify a name, a subdirectory will be * created for the attributes with the directory being the name of the * attribute group. */static struct attribute_group attr_group = {	.attrs = attrs,}; static struct kobject *example_kobj; static int example_init(void){	int retval; 	/*	 * Create a simple kobject with the name of "kobject_example",	 * located under /sys/kernel/	 *	 * As this is a simple directory, no uevent will be sent to	 * userspace.  That is why this function should not be used for	 * any type of dynamic kobjects, where the name and number are	 * not known ahead of time.	 */	example_kobj = kobject_create_and_add("kobject_example", kernel_kobj);	if (!example_kobj)		return -ENOMEM; 	/* Create the files associated with this kobject */	retval = sysfs_create_group(example_kobj, &attr_group);	if (retval)		kobject_put(example_kobj); 	return retval;} static void example_exit(void){	kobject_put(example_kobj);} module_init(example_init);module_exit(example_exit);MODULE_LICENSE("GPL");MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");