[deliverable/linux.git] / samples / kobject / kobject-example.c

/*
 * 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;
}

/* Sysfs attributes cannot be world-writable. */
static struct kobj_attribute foo_attribute =
	__ATTR(foo, 0664, foo_show, foo_store);

/*
 * More complex function where we determine which variable 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, 0664, b_show, b_store);
static struct kobj_attribute bar_attribute =
	__ATTR(bar, 0664, b_show, b_store);


/*
 * Create a group of attributes so that we can create and destroy 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 __init 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 __exit 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>");
Commit	Line	Data
40efcb05 GKH	1	/*
	2	* Sample kobject implementation
	3	*
	4	* Copyright (C) 2004-2007 Greg Kroah-Hartman <greg@kroah.com>
	5	* Copyright (C) 2007 Novell Inc.
	6	*
	7	* Released under the GPL version 2 only.
	8	*
	9	*/
	10	#include <linux/kobject.h>
	11	#include <linux/string.h>
	12	#include <linux/sysfs.h>
	13	#include <linux/module.h>
	14	#include <linux/init.h>
	15
	16	/*
	17	* This module shows how to create a simple subdirectory in sysfs called
	18	* /sys/kernel/kobject-example In that directory, 3 files are created:
	19	* "foo", "baz", and "bar". If an integer is written to these files, it can be
	20	* later read out of it.
	21	*/
	22
	23	static int foo;
	24	static int baz;
	25	static int bar;
	26
	27	/*
	28	* The "foo" file where a static variable is read from and written to.
	29	*/
	30	static ssize_t foo_show(struct kobject kobj, struct kobj_attribute attr,
	31	char *buf)
	32	{
	33	return sprintf(buf, "%d\n", foo);
	34	}
	35
	36	static ssize_t foo_store(struct kobject kobj, struct kobj_attribute attr,
	37	const char *buf, size_t count)
	38	{
	39	sscanf(buf, "%du", &foo);
	40	return count;
	41	}
	42
de510989	43	/* Sysfs attributes cannot be world-writable. */
40efcb05	44	static struct kobj_attribute foo_attribute =
de510989	45	__ATTR(foo, 0664, foo_show, foo_store);
40efcb05 GKH	46
40efcb05 GKH	47	/*
a115bc07	48	* More complex function where we determine which variable is being accessed by
40efcb05 GKH	49	* looking at the attribute for the "baz" and "bar" files.
	50	*/
	51	static ssize_t b_show(struct kobject kobj, struct kobj_attribute attr,
	52	char *buf)
	53	{
	54	int var;
	55
	56	if (strcmp(attr->attr.name, "baz") == 0)
	57	var = baz;
	58	else
	59	var = bar;
	60	return sprintf(buf, "%d\n", var);
	61	}
	62
	63	static ssize_t b_store(struct kobject kobj, struct kobj_attribute attr,
	64	const char *buf, size_t count)
	65	{
	66	int var;
	67
	68	sscanf(buf, "%du", &var);
	69	if (strcmp(attr->attr.name, "baz") == 0)
	70	baz = var;
	71	else
	72	bar = var;
	73	return count;
	74	}
	75
	76	static struct kobj_attribute baz_attribute =
de510989	77	__ATTR(baz, 0664, b_show, b_store);
40efcb05	78	static struct kobj_attribute bar_attribute =
de510989	79	__ATTR(bar, 0664, b_show, b_store);
40efcb05 GKH	80
	81
	82	/*
a115bc07	83	* Create a group of attributes so that we can create and destroy them all
40efcb05 GKH	84	* at once.
	85	*/
	86	static struct attribute *attrs[] = {
	87	&foo_attribute.attr,
	88	&baz_attribute.attr,
	89	&bar_attribute.attr,
	90	NULL, /* need to NULL terminate the list of attributes */
	91	};
	92
	93	/*
	94	* An unnamed attribute group will put all of the attributes directly in
	95	* the kobject directory. If we specify a name, a subdirectory will be
	96	* created for the attributes with the directory being the name of the
	97	* attribute group.
	98	*/
	99	static struct attribute_group attr_group = {
	100	.attrs = attrs,
	101	};
	102
	103	static struct kobject *example_kobj;
	104
7ec7fb39	105	static int __init example_init(void)
40efcb05 GKH	106	{
	107	int retval;
	108
	109	/*
	110	* Create a simple kobject with the name of "kobject_example",
	111	* located under /sys/kernel/
	112	*
	113	* As this is a simple directory, no uevent will be sent to
	114	* userspace. That is why this function should not be used for
	115	* any type of dynamic kobjects, where the name and number are
	116	* not known ahead of time.
	117	*/
	118	example_kobj = kobject_create_and_add("kobject_example", kernel_kobj);
	119	if (!example_kobj)
	120	return -ENOMEM;
	121
	122	/* Create the files associated with this kobject */
	123	retval = sysfs_create_group(example_kobj, &attr_group);
	124	if (retval)
	125	kobject_put(example_kobj);
	126
	127	return retval;
	128	}
	129
7ec7fb39	130	static void __exit example_exit(void)
40efcb05 GKH	131	{
	132	kobject_put(example_kobj);
	133	}
	134
	135	module_init(example_init);
	136	module_exit(example_exit);
	137	MODULE_LICENSE("GPL");
	138	MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");