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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 variable 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 destroy 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 |
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