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 
counter_device_release(struct device * dev)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, dev->id);
48 
49 	kfree(container_of(counter, struct counter_device_allochelper, counter));
50 }
51 
52 static const struct device_type counter_device_type = {
53 	.name = "counter_device",
54 	.release = counter_device_release,
55 };
56 
57 static const 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  */
counter_priv(const struct counter_device * const counter)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  */
counter_alloc(size_t sizeof_priv)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(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(&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, dev->id);
131 err_ida_alloc:
132 
133 	kfree(ch);
134 
135 	return NULL;
136 }
137 EXPORT_SYMBOL_NS_GPL(counter_alloc, COUNTER);
138 
counter_put(struct counter_device * counter)139 void counter_put(struct counter_device *counter)
140 {
141 	put_device(&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  */
counter_add(struct counter_device * counter)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(&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  */
counter_unregister(struct counter_device * const counter)178 void counter_unregister(struct counter_device *const counter)
179 {
180 	if (!counter)
181 		return;
182 
183 	cdev_device_del(&counter->chrdev, &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(&counter->ops_exist_lock);
191 }
192 EXPORT_SYMBOL_NS_GPL(counter_unregister, COUNTER);
193 
devm_counter_release(void * counter)194 static void devm_counter_release(void *counter)
195 {
196 	counter_unregister(counter);
197 }
198 
devm_counter_put(void * counter)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  */
devm_counter_alloc(struct device * dev,size_t sizeof_priv)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  */
devm_counter_add(struct device * dev,struct counter_device * const counter)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 
counter_init(void)252 static int __init counter_init(void)
253 {
254 	int err;
255 
256 	err = bus_register(&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(&counter_bus_type);
269 	return err;
270 }
271 
counter_exit(void)272 static void __exit counter_exit(void)
273 {
274 	unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX);
275 	bus_unregister(&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