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 */
 28static DEFINE_IDA(counter_ida);
 29
 30struct 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
 40static 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
 51static struct device_type counter_device_type = {
 52	.name = "counter_device",
 53	.release = counter_device_release,
 54};
 55
 56static struct bus_type counter_bus_type = {
 57	.name = "counter",
 58	.dev_name = "counter",
 59};
 60
 61static 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 */
 69void *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}
 76EXPORT_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 */
 87struct 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
124err_dev_set_name:
125
126	counter_chrdev_remove(counter);
127err_chrdev_add:
128
129	ida_free(&counter_ida, dev->id);
130err_ida_alloc:
131
132	kfree(ch);
133
134	return NULL;
135}
136EXPORT_SYMBOL_NS_GPL(counter_alloc, COUNTER);
137
138void counter_put(struct counter_device *counter)
139{
140	put_device(&counter->dev);
141}
142EXPORT_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 */
152int 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}
169EXPORT_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 */
177void 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}
191EXPORT_SYMBOL_NS_GPL(counter_unregister, COUNTER);
192
193static void devm_counter_release(void *counter)
194{
195	counter_unregister(counter);
196}
197
198static 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 */
211struct 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}
226EXPORT_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 */
236int 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}
247EXPORT_SYMBOL_NS_GPL(devm_counter_add, COUNTER);
248
249#define COUNTER_DEV_MAX 256
250
251static 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
266err_unregister_bus:
267	bus_unregister(&counter_bus_type);
268	return err;
269}
270
271static void __exit counter_exit(void)
272{
273	unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX);
274	bus_unregister(&counter_bus_type);
275}
276
277subsys_initcall(counter_init);
278module_exit(counter_exit);
279
280MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
281MODULE_DESCRIPTION("Generic Counter interface");
282MODULE_LICENSE("GPL v2");