2 * Sample kobject implementation
4 * Copyright (C) 2004-2007 Greg Kroah-Hartman <greg@kroah.com>
5 * Copyright (C) 2007 Novell Inc.
7 * Released under the GPL version 2 only.
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>
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.
28 * The "foo" file where a static variable is read from and written to.
30 static ssize_t
foo_show(struct kobject
*kobj
, struct kobj_attribute
*attr
,
33 return sprintf(buf
, "%d\n", foo
);
36 static ssize_t
foo_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
37 const char *buf
, size_t count
)
39 sscanf(buf
, "%du", &foo
);
43 static struct kobj_attribute foo_attribute
=
44 __ATTR(foo
, 0666, foo_show
, foo_store
);
47 * More complex function where we determine which varible is being accessed by
48 * looking at the attribute for the "baz" and "bar" files.
50 static ssize_t
b_show(struct kobject
*kobj
, struct kobj_attribute
*attr
,
55 if (strcmp(attr
->attr
.name
, "baz") == 0)
59 return sprintf(buf
, "%d\n", var
);
62 static ssize_t
b_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
63 const char *buf
, size_t count
)
67 sscanf(buf
, "%du", &var
);
68 if (strcmp(attr
->attr
.name
, "baz") == 0)
75 static struct kobj_attribute baz_attribute
=
76 __ATTR(baz
, 0666, b_show
, b_store
);
77 static struct kobj_attribute bar_attribute
=
78 __ATTR(bar
, 0666, b_show
, b_store
);
82 * Create a group of attributes so that we can create and destory them all
85 static struct attribute
*attrs
[] = {
89 NULL
, /* need to NULL terminate the list of attributes */
93 * An unnamed attribute group will put all of the attributes directly in
94 * the kobject directory. If we specify a name, a subdirectory will be
95 * created for the attributes with the directory being the name of the
98 static struct attribute_group attr_group
= {
102 static struct kobject
*example_kobj
;
104 static int example_init(void)
109 * Create a simple kobject with the name of "kobject_example",
110 * located under /sys/kernel/
112 * As this is a simple directory, no uevent will be sent to
113 * userspace. That is why this function should not be used for
114 * any type of dynamic kobjects, where the name and number are
115 * not known ahead of time.
117 example_kobj
= kobject_create_and_add("kobject_example", kernel_kobj
);
121 /* Create the files associated with this kobject */
122 retval
= sysfs_create_group(example_kobj
, &attr_group
);
124 kobject_put(example_kobj
);
129 static void example_exit(void)
131 kobject_put(example_kobj
);
134 module_init(example_init
);
135 module_exit(example_exit
);
136 MODULE_LICENSE("GPL");
137 MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");