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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 | { | |
5fd637e7 RB |
39 | int ret; |
40 | ||
41 | ret = kstrtoint(buf, 10, &foo); | |
42 | if (ret < 0) | |
43 | return ret; | |
44 | ||
40efcb05 GKH |
45 | return count; |
46 | } | |
47 | ||
de510989 | 48 | /* Sysfs attributes cannot be world-writable. */ |
40efcb05 | 49 | static struct kobj_attribute foo_attribute = |
de510989 | 50 | __ATTR(foo, 0664, foo_show, foo_store); |
40efcb05 GKH |
51 | |
52 | /* | |
a115bc07 | 53 | * More complex function where we determine which variable is being accessed by |
40efcb05 GKH |
54 | * looking at the attribute for the "baz" and "bar" files. |
55 | */ | |
56 | static ssize_t b_show(struct kobject *kobj, struct kobj_attribute *attr, | |
57 | char *buf) | |
58 | { | |
59 | int var; | |
60 | ||
61 | if (strcmp(attr->attr.name, "baz") == 0) | |
62 | var = baz; | |
63 | else | |
64 | var = bar; | |
65 | return sprintf(buf, "%d\n", var); | |
66 | } | |
67 | ||
68 | static ssize_t b_store(struct kobject *kobj, struct kobj_attribute *attr, | |
69 | const char *buf, size_t count) | |
70 | { | |
5fd637e7 RB |
71 | int var, ret; |
72 | ||
73 | ret = kstrtoint(buf, 10, &var); | |
74 | if (ret < 0) | |
75 | return ret; | |
40efcb05 | 76 | |
40efcb05 GKH |
77 | if (strcmp(attr->attr.name, "baz") == 0) |
78 | baz = var; | |
79 | else | |
80 | bar = var; | |
81 | return count; | |
82 | } | |
83 | ||
84 | static struct kobj_attribute baz_attribute = | |
de510989 | 85 | __ATTR(baz, 0664, b_show, b_store); |
40efcb05 | 86 | static struct kobj_attribute bar_attribute = |
de510989 | 87 | __ATTR(bar, 0664, b_show, b_store); |
40efcb05 GKH |
88 | |
89 | ||
90 | /* | |
a115bc07 | 91 | * Create a group of attributes so that we can create and destroy them all |
40efcb05 GKH |
92 | * at once. |
93 | */ | |
94 | static struct attribute *attrs[] = { | |
95 | &foo_attribute.attr, | |
96 | &baz_attribute.attr, | |
97 | &bar_attribute.attr, | |
98 | NULL, /* need to NULL terminate the list of attributes */ | |
99 | }; | |
100 | ||
101 | /* | |
102 | * An unnamed attribute group will put all of the attributes directly in | |
103 | * the kobject directory. If we specify a name, a subdirectory will be | |
104 | * created for the attributes with the directory being the name of the | |
105 | * attribute group. | |
106 | */ | |
107 | static struct attribute_group attr_group = { | |
108 | .attrs = attrs, | |
109 | }; | |
110 | ||
111 | static struct kobject *example_kobj; | |
112 | ||
7ec7fb39 | 113 | static int __init example_init(void) |
40efcb05 GKH |
114 | { |
115 | int retval; | |
116 | ||
117 | /* | |
118 | * Create a simple kobject with the name of "kobject_example", | |
119 | * located under /sys/kernel/ | |
120 | * | |
121 | * As this is a simple directory, no uevent will be sent to | |
122 | * userspace. That is why this function should not be used for | |
123 | * any type of dynamic kobjects, where the name and number are | |
124 | * not known ahead of time. | |
125 | */ | |
126 | example_kobj = kobject_create_and_add("kobject_example", kernel_kobj); | |
127 | if (!example_kobj) | |
128 | return -ENOMEM; | |
129 | ||
130 | /* Create the files associated with this kobject */ | |
131 | retval = sysfs_create_group(example_kobj, &attr_group); | |
132 | if (retval) | |
133 | kobject_put(example_kobj); | |
134 | ||
135 | return retval; | |
136 | } | |
137 | ||
7ec7fb39 | 138 | static void __exit example_exit(void) |
40efcb05 GKH |
139 | { |
140 | kobject_put(example_kobj); | |
141 | } | |
142 | ||
143 | module_init(example_init); | |
144 | module_exit(example_exit); | |
07afb6ac | 145 | MODULE_LICENSE("GPL v2"); |
40efcb05 | 146 | MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>"); |