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 
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  */
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_GPL(counter_priv);
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  */
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_GPL(counter_alloc);
137 
138 void counter_put(struct counter_device *counter)
139 {
140 	put_device(&counter->dev);
141 }
142 EXPORT_SYMBOL_GPL(counter_put);
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  */
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_GPL(counter_add);
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  */
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_GPL(counter_unregister);
192 
193 static void devm_counter_release(void *counter)
194 {
195 	counter_unregister(counter);
196 }
197 
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  */
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_GPL(devm_counter_alloc);
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  */
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_GPL(devm_counter_add);
248 
249 #define COUNTER_DEV_MAX 256
250 
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 
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