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
43 static struct kobj_attribute foo_attribute =
44 __ATTR(foo, 0666, foo_show, foo_store);
45
46 /*
47 * More complex function where we determine which varible is being accessed by
48 * looking at the attribute for the "baz" and "bar" files.
49 */
50 static ssize_t b_show(struct kobject *kobj, struct kobj_attribute *attr,
51 char *buf)
52 {
53 int var;
54
55 if (strcmp(attr->attr.name, "baz") == 0)
56 var = baz;
57 else
58 var = bar;
59 return sprintf(buf, "%d\n", var);
60 }
61
62 static ssize_t b_store(struct kobject *kobj, struct kobj_attribute *attr,
63 const char *buf, size_t count)
64 {
65 int var;
66
67 sscanf(buf, "%du", &var);
68 if (strcmp(attr->attr.name, "baz") == 0)
69 baz = var;
70 else
71 bar = var;
72 return count;
73 }
74
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);
79
80
81 /*
82 * Create a group of attributes so that we can create and destory them all
83 * at once.
84 */
85 static struct attribute *attrs[] = {
86 &foo_attribute.attr,
87 &baz_attribute.attr,
88 &bar_attribute.attr,
89 NULL, /* need to NULL terminate the list of attributes */
90 };
91
92 /*
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
96 * attribute group.
97 */
98 static struct attribute_group attr_group = {
99 .attrs = attrs,
100 };
101
102 static struct kobject *example_kobj;
103
104 static int __init example_init(void)
105 {
106 int retval;
107
108 /*
109 * Create a simple kobject with the name of "kobject_example",
110 * located under /sys/kernel/
111 *
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.
116 */
117 example_kobj = kobject_create_and_add("kobject_example", kernel_kobj);
118 if (!example_kobj)
119 return -ENOMEM;
120
121 /* Create the files associated with this kobject */
122 retval = sysfs_create_group(example_kobj, &attr_group);
123 if (retval)
124 kobject_put(example_kobj);
125
126 return retval;
127 }
128
129 static void __exit example_exit(void)
130 {
131 kobject_put(example_kobj);
132 }
133
134 module_init(example_init);
135 module_exit(example_exit);
136 MODULE_LICENSE("GPL");
137 MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");
138
|
This page was automatically generated by the
LXR engine.
|