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 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
 41static 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
 52static struct device_type counter_device_type = {
 53	.name = "counter_device",
 54	.release = counter_device_release,
 55};
 56
 57static struct bus_type counter_bus_type = {
 58	.name = "counter",
 59	.dev_name = "counter",
 60};
 61
 62static 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 */
 70void *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}
 77EXPORT_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 */
 88struct 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
125err_dev_set_name:
126
127	counter_chrdev_remove(counter);
128err_chrdev_add:
129
130	ida_free(&counter_ida, dev->id);
131err_ida_alloc:
132
133	kfree(ch);
134
135	return NULL;
136}
137EXPORT_SYMBOL_NS_GPL(counter_alloc, COUNTER);
138
139void counter_put(struct counter_device *counter)
140{
141	put_device(&counter->dev);
142}
143EXPORT_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 */
153int 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}
170EXPORT_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 */
178void 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}
192EXPORT_SYMBOL_NS_GPL(counter_unregister, COUNTER);
193
194static void devm_counter_release(void *counter)
195{
196	counter_unregister(counter);
197}
198
199static 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 */
212struct 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}
227EXPORT_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 */
237int 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}
248EXPORT_SYMBOL_NS_GPL(devm_counter_add, COUNTER);
249
250#define COUNTER_DEV_MAX 256
251
252static 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
267err_unregister_bus:
268	bus_unregister(&counter_bus_type);
269	return err;
270}
271
272static void __exit counter_exit(void)
273{
274	unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX);
275	bus_unregister(&counter_bus_type);
276}
277
278subsys_initcall(counter_init);
279module_exit(counter_exit);
280
281MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
282MODULE_DESCRIPTION("Generic Counter interface");
283MODULE_LICENSE("GPL v2");