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1 | /* |
2 | * Sample kset and ktype 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/slab.h> |
14 | #include <linux/module.h> |
15 | #include <linux/init.h> |
16 | |
17 | /* |
18 | * This module shows how to create a kset in sysfs called |
19 | * /sys/kernel/kset-example |
20 | * Then tree kobjects are created and assigned to this kset, "foo", "baz", |
21 | * and "bar". In those kobjects, attributes of the same name are also |
22 | * created and if an integer is written to these files, it can be later |
23 | * read out of it. |
24 | */ |
25 | |
26 | |
27 | /* |
28 | * This is our "object" that we will create a few of and register them with |
29 | * sysfs. |
30 | */ |
31 | struct foo_obj { |
32 | struct kobject kobj; |
33 | int foo; |
34 | int baz; |
35 | int bar; |
36 | }; |
37 | #define to_foo_obj(x) container_of(x, struct foo_obj, kobj) |
38 | |
39 | /* a custom attribute that works just for a struct foo_obj. */ |
40 | struct foo_attribute { |
41 | struct attribute attr; |
42 | ssize_t (*show)(struct foo_obj *foo, struct foo_attribute *attr, char *buf); |
43 | ssize_t (*store)(struct foo_obj *foo, struct foo_attribute *attr, const char *buf, size_t count); |
44 | }; |
45 | #define to_foo_attr(x) container_of(x, struct foo_attribute, attr) |
46 | |
47 | /* |
48 | * The default show function that must be passed to sysfs. This will be |
49 | * called by sysfs for whenever a show function is called by the user on a |
50 | * sysfs file associated with the kobjects we have registered. We need to |
51 | * transpose back from a "default" kobject to our custom struct foo_obj and |
52 | * then call the show function for that specific object. |
53 | */ |
54 | static ssize_t foo_attr_show(struct kobject *kobj, |
55 | struct attribute *attr, |
56 | char *buf) |
57 | { |
58 | struct foo_attribute *attribute; |
59 | struct foo_obj *foo; |
60 | |
61 | attribute = to_foo_attr(attr); |
62 | foo = to_foo_obj(kobj); |
63 | |
64 | if (!attribute->show) |
65 | return -EIO; |
66 | |
67 | return attribute->show(foo, attribute, buf); |
68 | } |
69 | |
70 | /* |
71 | * Just like the default show function above, but this one is for when the |
72 | * sysfs "store" is requested (when a value is written to a file.) |
73 | */ |
74 | static ssize_t foo_attr_store(struct kobject *kobj, |
75 | struct attribute *attr, |
76 | const char *buf, size_t len) |
77 | { |
78 | struct foo_attribute *attribute; |
79 | struct foo_obj *foo; |
80 | |
81 | attribute = to_foo_attr(attr); |
82 | foo = to_foo_obj(kobj); |
83 | |
84 | if (!attribute->store) |
85 | return -EIO; |
86 | |
87 | return attribute->store(foo, attribute, buf, len); |
88 | } |
89 | |
90 | /* Our custom sysfs_ops that we will associate with our ktype later on */ |
91 | static const struct sysfs_ops foo_sysfs_ops = { |
92 | .show = foo_attr_show, |
93 | .store = foo_attr_store, |
94 | }; |
95 | |
96 | /* |
97 | * The release function for our object. This is REQUIRED by the kernel to |
98 | * have. We free the memory held in our object here. |
99 | * |
100 | * NEVER try to get away with just a "blank" release function to try to be |
101 | * smarter than the kernel. Turns out, no one ever is... |
102 | */ |
103 | static void foo_release(struct kobject *kobj) |
104 | { |
105 | struct foo_obj *foo; |
106 | |
107 | foo = to_foo_obj(kobj); |
108 | kfree(foo); |
109 | } |
110 | |
111 | /* |
112 | * The "foo" file where the .foo variable is read from and written to. |
113 | */ |
114 | static ssize_t foo_show(struct foo_obj *foo_obj, struct foo_attribute *attr, |
115 | char *buf) |
116 | { |
117 | return sprintf(buf, "%d\n", foo_obj->foo); |
118 | } |
119 | |
120 | static ssize_t foo_store(struct foo_obj *foo_obj, struct foo_attribute *attr, |
121 | const char *buf, size_t count) |
122 | { |
123 | sscanf(buf, "%du", &foo_obj->foo); |
124 | return count; |
125 | } |
126 | |
127 | static struct foo_attribute foo_attribute = |
128 | __ATTR(foo, 0666, foo_show, foo_store); |
129 | |
130 | /* |
131 | * More complex function where we determine which variable is being accessed by |
132 | * looking at the attribute for the "baz" and "bar" files. |
133 | */ |
134 | static ssize_t b_show(struct foo_obj *foo_obj, struct foo_attribute *attr, |
135 | char *buf) |
136 | { |
137 | int var; |
138 | |
139 | if (strcmp(attr->attr.name, "baz") == 0) |
140 | var = foo_obj->baz; |
141 | else |
142 | var = foo_obj->bar; |
143 | return sprintf(buf, "%d\n", var); |
144 | } |
145 | |
146 | static ssize_t b_store(struct foo_obj *foo_obj, struct foo_attribute *attr, |
147 | const char *buf, size_t count) |
148 | { |
149 | int var; |
150 | |
151 | sscanf(buf, "%du", &var); |
152 | if (strcmp(attr->attr.name, "baz") == 0) |
153 | foo_obj->baz = var; |
154 | else |
155 | foo_obj->bar = var; |
156 | return count; |
157 | } |
158 | |
159 | static struct foo_attribute baz_attribute = |
160 | __ATTR(baz, 0666, b_show, b_store); |
161 | static struct foo_attribute bar_attribute = |
162 | __ATTR(bar, 0666, b_show, b_store); |
163 | |
164 | /* |
165 | * Create a group of attributes so that we can create and destroy them all |
166 | * at once. |
167 | */ |
168 | static struct attribute *foo_default_attrs[] = { |
169 | &foo_attribute.attr, |
170 | &baz_attribute.attr, |
171 | &bar_attribute.attr, |
172 | NULL, /* need to NULL terminate the list of attributes */ |
173 | }; |
174 | |
175 | /* |
176 | * Our own ktype for our kobjects. Here we specify our sysfs ops, the |
177 | * release function, and the set of default attributes we want created |
178 | * whenever a kobject of this type is registered with the kernel. |
179 | */ |
180 | static struct kobj_type foo_ktype = { |
181 | .sysfs_ops = &foo_sysfs_ops, |
182 | .release = foo_release, |
183 | .default_attrs = foo_default_attrs, |
184 | }; |
185 | |
186 | static struct kset *example_kset; |
187 | static struct foo_obj *foo_obj; |
188 | static struct foo_obj *bar_obj; |
189 | static struct foo_obj *baz_obj; |
190 | |
191 | static struct foo_obj *create_foo_obj(const char *name) |
192 | { |
193 | struct foo_obj *foo; |
194 | int retval; |
195 | |
196 | /* allocate the memory for the whole object */ |
197 | foo = kzalloc(sizeof(*foo), GFP_KERNEL); |
198 | if (!foo) |
199 | return NULL; |
200 | |
201 | /* |
202 | * As we have a kset for this kobject, we need to set it before calling |
203 | * the kobject core. |
204 | */ |
205 | foo->kobj.kset = example_kset; |
206 | |
207 | /* |
208 | * Initialize and add the kobject to the kernel. All the default files |
209 | * will be created here. As we have already specified a kset for this |
210 | * kobject, we don't have to set a parent for the kobject, the kobject |
211 | * will be placed beneath that kset automatically. |
212 | */ |
213 | retval = kobject_init_and_add(&foo->kobj, &foo_ktype, NULL, "%s", name); |
214 | if (retval) { |
215 | kobject_put(&foo->kobj); |
216 | return NULL; |
217 | } |
218 | |
219 | /* |
220 | * We are always responsible for sending the uevent that the kobject |
221 | * was added to the system. |
222 | */ |
223 | kobject_uevent(&foo->kobj, KOBJ_ADD); |
224 | |
225 | return foo; |
226 | } |
227 | |
228 | static void destroy_foo_obj(struct foo_obj *foo) |
229 | { |
230 | kobject_put(&foo->kobj); |
231 | } |
232 | |
233 | static int __init example_init(void) |
234 | { |
235 | /* |
236 | * Create a kset with the name of "kset_example", |
237 | * located under /sys/kernel/ |
238 | */ |
239 | example_kset = kset_create_and_add("kset_example", NULL, kernel_kobj); |
240 | if (!example_kset) |
241 | return -ENOMEM; |
242 | |
243 | /* |
244 | * Create three objects and register them with our kset |
245 | */ |
246 | foo_obj = create_foo_obj("foo"); |
247 | if (!foo_obj) |
248 | goto foo_error; |
249 | |
250 | bar_obj = create_foo_obj("bar"); |
251 | if (!bar_obj) |
252 | goto bar_error; |
253 | |
254 | baz_obj = create_foo_obj("baz"); |
255 | if (!baz_obj) |
256 | goto baz_error; |
257 | |
258 | return 0; |
259 | |
260 | baz_error: |
261 | destroy_foo_obj(bar_obj); |
262 | bar_error: |
263 | destroy_foo_obj(foo_obj); |
264 | foo_error: |
265 | return -EINVAL; |
266 | } |
267 | |
268 | static void __exit example_exit(void) |
269 | { |
270 | destroy_foo_obj(baz_obj); |
271 | destroy_foo_obj(bar_obj); |
272 | destroy_foo_obj(foo_obj); |
273 | kset_unregister(example_kset); |
274 | } |
275 | |
276 | module_init(example_init); |
277 | module_exit(example_exit); |
278 | MODULE_LICENSE("GPL"); |
279 | MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>"); |
280 |
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