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 ensures private data behaves like if it were kmalloced |
35 | * separately. Also ensures the minimum alignment for safe DMA |
36 | * operations (which may or may not mean cache alignment). |
37 | */ |
38 | unsigned long privdata[] __aligned(ARCH_DMA_MINALIGN); |
39 | }; |
40 | |
41 | static void counter_device_release(struct device *dev) |
42 | { |
43 | struct counter_device *const counter = |
44 | container_of(dev, struct counter_device, dev); |
45 | |
46 | counter_chrdev_remove(counter); |
47 | ida_free(&counter_ida, id: dev->id); |
48 | |
49 | kfree(container_of(counter, struct counter_device_allochelper, counter)); |
50 | } |
51 | |
52 | static struct device_type counter_device_type = { |
53 | .name = "counter_device" , |
54 | .release = counter_device_release, |
55 | }; |
56 | |
57 | static struct bus_type counter_bus_type = { |
58 | .name = "counter" , |
59 | .dev_name = "counter" , |
60 | }; |
61 | |
62 | static dev_t counter_devt; |
63 | |
64 | /** |
65 | * counter_priv - access counter device private data |
66 | * @counter: counter device |
67 | * |
68 | * Get the counter device private data |
69 | */ |
70 | void *counter_priv(const struct counter_device *const counter) |
71 | { |
72 | struct counter_device_allochelper *ch = |
73 | container_of(counter, struct counter_device_allochelper, counter); |
74 | |
75 | return &ch->privdata; |
76 | } |
77 | EXPORT_SYMBOL_NS_GPL(counter_priv, COUNTER); |
78 | |
79 | /** |
80 | * counter_alloc - allocate a counter_device |
81 | * @sizeof_priv: size of the driver private data |
82 | * |
83 | * This is part one of counter registration. The structure is allocated |
84 | * dynamically to ensure the right lifetime for the embedded struct device. |
85 | * |
86 | * If this succeeds, call counter_put() to get rid of the counter_device again. |
87 | */ |
88 | struct counter_device *counter_alloc(size_t sizeof_priv) |
89 | { |
90 | struct counter_device_allochelper *ch; |
91 | struct counter_device *counter; |
92 | struct device *dev; |
93 | int err; |
94 | |
95 | ch = kzalloc(size: sizeof(*ch) + sizeof_priv, GFP_KERNEL); |
96 | if (!ch) |
97 | return NULL; |
98 | |
99 | counter = &ch->counter; |
100 | dev = &counter->dev; |
101 | |
102 | /* Acquire unique ID */ |
103 | err = ida_alloc(ida: &counter_ida, GFP_KERNEL); |
104 | if (err < 0) |
105 | goto err_ida_alloc; |
106 | dev->id = err; |
107 | |
108 | mutex_init(&counter->ops_exist_lock); |
109 | dev->type = &counter_device_type; |
110 | dev->bus = &counter_bus_type; |
111 | dev->devt = MKDEV(MAJOR(counter_devt), dev->id); |
112 | |
113 | err = counter_chrdev_add(counter); |
114 | if (err < 0) |
115 | goto err_chrdev_add; |
116 | |
117 | device_initialize(dev); |
118 | |
119 | err = dev_set_name(dev, COUNTER_NAME "%d" , dev->id); |
120 | if (err) |
121 | goto err_dev_set_name; |
122 | |
123 | return counter; |
124 | |
125 | err_dev_set_name: |
126 | |
127 | counter_chrdev_remove(counter); |
128 | err_chrdev_add: |
129 | |
130 | ida_free(&counter_ida, id: dev->id); |
131 | err_ida_alloc: |
132 | |
133 | kfree(objp: ch); |
134 | |
135 | return NULL; |
136 | } |
137 | EXPORT_SYMBOL_NS_GPL(counter_alloc, COUNTER); |
138 | |
139 | void counter_put(struct counter_device *counter) |
140 | { |
141 | put_device(dev: &counter->dev); |
142 | } |
143 | EXPORT_SYMBOL_NS_GPL(counter_put, COUNTER); |
144 | |
145 | /** |
146 | * counter_add - complete registration of a counter |
147 | * @counter: the counter to add |
148 | * |
149 | * This is part two of counter registration. |
150 | * |
151 | * If this succeeds, call counter_unregister() to get rid of the counter_device again. |
152 | */ |
153 | int counter_add(struct counter_device *counter) |
154 | { |
155 | int err; |
156 | struct device *dev = &counter->dev; |
157 | |
158 | if (counter->parent) { |
159 | dev->parent = counter->parent; |
160 | dev->of_node = counter->parent->of_node; |
161 | } |
162 | |
163 | err = counter_sysfs_add(counter); |
164 | if (err < 0) |
165 | return err; |
166 | |
167 | /* implies device_add(dev) */ |
168 | return cdev_device_add(cdev: &counter->chrdev, dev); |
169 | } |
170 | EXPORT_SYMBOL_NS_GPL(counter_add, COUNTER); |
171 | |
172 | /** |
173 | * counter_unregister - unregister Counter from the system |
174 | * @counter: pointer to Counter to unregister |
175 | * |
176 | * The Counter is unregistered from the system. |
177 | */ |
178 | void counter_unregister(struct counter_device *const counter) |
179 | { |
180 | if (!counter) |
181 | return; |
182 | |
183 | cdev_device_del(cdev: &counter->chrdev, dev: &counter->dev); |
184 | |
185 | mutex_lock(&counter->ops_exist_lock); |
186 | |
187 | counter->ops = NULL; |
188 | wake_up(&counter->events_wait); |
189 | |
190 | mutex_unlock(lock: &counter->ops_exist_lock); |
191 | } |
192 | EXPORT_SYMBOL_NS_GPL(counter_unregister, COUNTER); |
193 | |
194 | static void devm_counter_release(void *counter) |
195 | { |
196 | counter_unregister(counter); |
197 | } |
198 | |
199 | static void devm_counter_put(void *counter) |
200 | { |
201 | counter_put(counter); |
202 | } |
203 | |
204 | /** |
205 | * devm_counter_alloc - allocate a counter_device |
206 | * @dev: the device to register the release callback for |
207 | * @sizeof_priv: size of the driver private data |
208 | * |
209 | * This is the device managed version of counter_add(). It registers a cleanup |
210 | * callback to care for calling counter_put(). |
211 | */ |
212 | struct counter_device *devm_counter_alloc(struct device *dev, size_t sizeof_priv) |
213 | { |
214 | struct counter_device *counter; |
215 | int err; |
216 | |
217 | counter = counter_alloc(sizeof_priv); |
218 | if (!counter) |
219 | return NULL; |
220 | |
221 | err = devm_add_action_or_reset(dev, devm_counter_put, counter); |
222 | if (err < 0) |
223 | return NULL; |
224 | |
225 | return counter; |
226 | } |
227 | EXPORT_SYMBOL_NS_GPL(devm_counter_alloc, COUNTER); |
228 | |
229 | /** |
230 | * devm_counter_add - complete registration of a counter |
231 | * @dev: the device to register the release callback for |
232 | * @counter: the counter to add |
233 | * |
234 | * This is the device managed version of counter_add(). It registers a cleanup |
235 | * callback to care for calling counter_unregister(). |
236 | */ |
237 | int devm_counter_add(struct device *dev, |
238 | struct counter_device *const counter) |
239 | { |
240 | int err; |
241 | |
242 | err = counter_add(counter); |
243 | if (err < 0) |
244 | return err; |
245 | |
246 | return devm_add_action_or_reset(dev, devm_counter_release, counter); |
247 | } |
248 | EXPORT_SYMBOL_NS_GPL(devm_counter_add, COUNTER); |
249 | |
250 | #define COUNTER_DEV_MAX 256 |
251 | |
252 | static int __init counter_init(void) |
253 | { |
254 | int err; |
255 | |
256 | err = bus_register(bus: &counter_bus_type); |
257 | if (err < 0) |
258 | return err; |
259 | |
260 | err = alloc_chrdev_region(&counter_devt, 0, COUNTER_DEV_MAX, |
261 | COUNTER_NAME); |
262 | if (err < 0) |
263 | goto err_unregister_bus; |
264 | |
265 | return 0; |
266 | |
267 | err_unregister_bus: |
268 | bus_unregister(bus: &counter_bus_type); |
269 | return err; |
270 | } |
271 | |
272 | static void __exit counter_exit(void) |
273 | { |
274 | unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX); |
275 | bus_unregister(bus: &counter_bus_type); |
276 | } |
277 | |
278 | subsys_initcall(counter_init); |
279 | module_exit(counter_exit); |
280 | |
281 | MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>" ); |
282 | MODULE_DESCRIPTION("Generic Counter interface" ); |
283 | MODULE_LICENSE("GPL v2" ); |
284 | |