1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Generic Counter interface
4 * Copyright (C) 2020 William Breathitt Gray
5 */
6 #include <linux/cdev.h>
7 #include <linux/counter.h>
8 #include <linux/device.h>
9 #include <linux/device/bus.h>
10 #include <linux/export.h>
11 #include <linux/fs.h>
12 #include <linux/gfp.h>
13 #include <linux/idr.h>
14 #include <linux/init.h>
15 #include <linux/kdev_t.h>
16 #include <linux/module.h>
17 #include <linux/mutex.h>
18 #include <linux/slab.h>
19 #include <linux/types.h>
20 #include <linux/wait.h>
21
22 #include "counter-chrdev.h"
23 #include "counter-sysfs.h"
24
25 #define COUNTER_NAME "counter"
26
27 /* Provides a unique ID for each counter device */
28 static DEFINE_IDA(counter_ida);
29
30 struct counter_device_allochelper {
31 struct counter_device counter;
32
33 /*
34 * This is cache line aligned to ensure private data behaves like if it
35 * were kmalloced separately.
36 */
37 unsigned long privdata[] ____cacheline_aligned;
38 };
39
counter_device_release(struct device * dev)40 static void counter_device_release(struct device *dev)
41 {
42 struct counter_device *const counter =
43 container_of(dev, struct counter_device, dev);
44
45 counter_chrdev_remove(counter);
46 ida_free(&counter_ida, dev->id);
47
48 kfree(container_of(counter, struct counter_device_allochelper, counter));
49 }
50
51 static struct device_type counter_device_type = {
52 .name = "counter_device",
53 .release = counter_device_release,
54 };
55
56 static struct bus_type counter_bus_type = {
57 .name = "counter",
58 .dev_name = "counter",
59 };
60
61 static dev_t counter_devt;
62
63 /**
64 * counter_priv - access counter device private data
65 * @counter: counter device
66 *
67 * Get the counter device private data
68 */
counter_priv(const struct counter_device * const counter)69 void *counter_priv(const struct counter_device *const counter)
70 {
71 struct counter_device_allochelper *ch =
72 container_of(counter, struct counter_device_allochelper, counter);
73
74 return &ch->privdata;
75 }
76 EXPORT_SYMBOL_NS_GPL(counter_priv, COUNTER);
77
78 /**
79 * counter_alloc - allocate a counter_device
80 * @sizeof_priv: size of the driver private data
81 *
82 * This is part one of counter registration. The structure is allocated
83 * dynamically to ensure the right lifetime for the embedded struct device.
84 *
85 * If this succeeds, call counter_put() to get rid of the counter_device again.
86 */
counter_alloc(size_t sizeof_priv)87 struct counter_device *counter_alloc(size_t sizeof_priv)
88 {
89 struct counter_device_allochelper *ch;
90 struct counter_device *counter;
91 struct device *dev;
92 int err;
93
94 ch = kzalloc(sizeof(*ch) + sizeof_priv, GFP_KERNEL);
95 if (!ch)
96 return NULL;
97
98 counter = &ch->counter;
99 dev = &counter->dev;
100
101 /* Acquire unique ID */
102 err = ida_alloc(&counter_ida, GFP_KERNEL);
103 if (err < 0)
104 goto err_ida_alloc;
105 dev->id = err;
106
107 mutex_init(&counter->ops_exist_lock);
108 dev->type = &counter_device_type;
109 dev->bus = &counter_bus_type;
110 dev->devt = MKDEV(MAJOR(counter_devt), dev->id);
111
112 err = counter_chrdev_add(counter);
113 if (err < 0)
114 goto err_chrdev_add;
115
116 device_initialize(dev);
117
118 err = dev_set_name(dev, COUNTER_NAME "%d", dev->id);
119 if (err)
120 goto err_dev_set_name;
121
122 return counter;
123
124 err_dev_set_name:
125
126 counter_chrdev_remove(counter);
127 err_chrdev_add:
128
129 ida_free(&counter_ida, dev->id);
130 err_ida_alloc:
131
132 kfree(ch);
133
134 return NULL;
135 }
136 EXPORT_SYMBOL_NS_GPL(counter_alloc, COUNTER);
137
counter_put(struct counter_device * counter)138 void counter_put(struct counter_device *counter)
139 {
140 put_device(&counter->dev);
141 }
142 EXPORT_SYMBOL_NS_GPL(counter_put, COUNTER);
143
144 /**
145 * counter_add - complete registration of a counter
146 * @counter: the counter to add
147 *
148 * This is part two of counter registration.
149 *
150 * If this succeeds, call counter_unregister() to get rid of the counter_device again.
151 */
counter_add(struct counter_device * counter)152 int counter_add(struct counter_device *counter)
153 {
154 int err;
155 struct device *dev = &counter->dev;
156
157 if (counter->parent) {
158 dev->parent = counter->parent;
159 dev->of_node = counter->parent->of_node;
160 }
161
162 err = counter_sysfs_add(counter);
163 if (err < 0)
164 return err;
165
166 /* implies device_add(dev) */
167 return cdev_device_add(&counter->chrdev, dev);
168 }
169 EXPORT_SYMBOL_NS_GPL(counter_add, COUNTER);
170
171 /**
172 * counter_unregister - unregister Counter from the system
173 * @counter: pointer to Counter to unregister
174 *
175 * The Counter is unregistered from the system.
176 */
counter_unregister(struct counter_device * const counter)177 void counter_unregister(struct counter_device *const counter)
178 {
179 if (!counter)
180 return;
181
182 cdev_device_del(&counter->chrdev, &counter->dev);
183
184 mutex_lock(&counter->ops_exist_lock);
185
186 counter->ops = NULL;
187 wake_up(&counter->events_wait);
188
189 mutex_unlock(&counter->ops_exist_lock);
190 }
191 EXPORT_SYMBOL_NS_GPL(counter_unregister, COUNTER);
192
devm_counter_release(void * counter)193 static void devm_counter_release(void *counter)
194 {
195 counter_unregister(counter);
196 }
197
devm_counter_put(void * counter)198 static void devm_counter_put(void *counter)
199 {
200 counter_put(counter);
201 }
202
203 /**
204 * devm_counter_alloc - allocate a counter_device
205 * @dev: the device to register the release callback for
206 * @sizeof_priv: size of the driver private data
207 *
208 * This is the device managed version of counter_add(). It registers a cleanup
209 * callback to care for calling counter_put().
210 */
devm_counter_alloc(struct device * dev,size_t sizeof_priv)211 struct counter_device *devm_counter_alloc(struct device *dev, size_t sizeof_priv)
212 {
213 struct counter_device *counter;
214 int err;
215
216 counter = counter_alloc(sizeof_priv);
217 if (!counter)
218 return NULL;
219
220 err = devm_add_action_or_reset(dev, devm_counter_put, counter);
221 if (err < 0)
222 return NULL;
223
224 return counter;
225 }
226 EXPORT_SYMBOL_NS_GPL(devm_counter_alloc, COUNTER);
227
228 /**
229 * devm_counter_add - complete registration of a counter
230 * @dev: the device to register the release callback for
231 * @counter: the counter to add
232 *
233 * This is the device managed version of counter_add(). It registers a cleanup
234 * callback to care for calling counter_unregister().
235 */
devm_counter_add(struct device * dev,struct counter_device * const counter)236 int devm_counter_add(struct device *dev,
237 struct counter_device *const counter)
238 {
239 int err;
240
241 err = counter_add(counter);
242 if (err < 0)
243 return err;
244
245 return devm_add_action_or_reset(dev, devm_counter_release, counter);
246 }
247 EXPORT_SYMBOL_NS_GPL(devm_counter_add, COUNTER);
248
249 #define COUNTER_DEV_MAX 256
250
counter_init(void)251 static int __init counter_init(void)
252 {
253 int err;
254
255 err = bus_register(&counter_bus_type);
256 if (err < 0)
257 return err;
258
259 err = alloc_chrdev_region(&counter_devt, 0, COUNTER_DEV_MAX,
260 COUNTER_NAME);
261 if (err < 0)
262 goto err_unregister_bus;
263
264 return 0;
265
266 err_unregister_bus:
267 bus_unregister(&counter_bus_type);
268 return err;
269 }
270
counter_exit(void)271 static void __exit counter_exit(void)
272 {
273 unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX);
274 bus_unregister(&counter_bus_type);
275 }
276
277 subsys_initcall(counter_init);
278 module_exit(counter_exit);
279
280 MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
281 MODULE_DESCRIPTION("Generic Counter interface");
282 MODULE_LICENSE("GPL v2");
283