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/types.h>
19 #include <linux/wait.h>
20 
21 #include "counter-chrdev.h"
22 #include "counter-sysfs.h"
23 
24 /* Provides a unique ID for each counter device */
25 static DEFINE_IDA(counter_ida);
26 
counter_device_release(struct device * dev)27 static void counter_device_release(struct device *dev)
28 {
29 	struct counter_device *const counter = dev_get_drvdata(dev);
30 
31 	counter_chrdev_remove(counter);
32 	ida_free(&counter_ida, dev->id);
33 }
34 
35 static struct device_type counter_device_type = {
36 	.name = "counter_device",
37 	.release = counter_device_release,
38 };
39 
40 static struct bus_type counter_bus_type = {
41 	.name = "counter",
42 	.dev_name = "counter",
43 };
44 
45 static dev_t counter_devt;
46 
47 /**
48  * counter_register - register Counter to the system
49  * @counter:	pointer to Counter to register
50  *
51  * This function registers a Counter to the system. A sysfs "counter" directory
52  * will be created and populated with sysfs attributes correlating with the
53  * Counter Signals, Synapses, and Counts respectively.
54  *
55  * RETURNS:
56  * 0 on success, negative error number on failure.
57  */
counter_register(struct counter_device * const counter)58 int counter_register(struct counter_device *const counter)
59 {
60 	struct device *const dev = &counter->dev;
61 	int id;
62 	int err;
63 
64 	/* Acquire unique ID */
65 	id = ida_alloc(&counter_ida, GFP_KERNEL);
66 	if (id < 0)
67 		return id;
68 
69 	mutex_init(&counter->ops_exist_lock);
70 
71 	/* Configure device structure for Counter */
72 	dev->id = id;
73 	dev->type = &counter_device_type;
74 	dev->bus = &counter_bus_type;
75 	dev->devt = MKDEV(MAJOR(counter_devt), id);
76 	if (counter->parent) {
77 		dev->parent = counter->parent;
78 		dev->of_node = counter->parent->of_node;
79 	}
80 	device_initialize(dev);
81 	dev_set_drvdata(dev, counter);
82 
83 	err = counter_sysfs_add(counter);
84 	if (err < 0)
85 		goto err_free_id;
86 
87 	err = counter_chrdev_add(counter);
88 	if (err < 0)
89 		goto err_free_id;
90 
91 	err = cdev_device_add(&counter->chrdev, dev);
92 	if (err < 0)
93 		goto err_remove_chrdev;
94 
95 	return 0;
96 
97 err_remove_chrdev:
98 	counter_chrdev_remove(counter);
99 err_free_id:
100 	put_device(dev);
101 	return err;
102 }
103 EXPORT_SYMBOL_GPL(counter_register);
104 
105 /**
106  * counter_unregister - unregister Counter from the system
107  * @counter:	pointer to Counter to unregister
108  *
109  * The Counter is unregistered from the system.
110  */
counter_unregister(struct counter_device * const counter)111 void counter_unregister(struct counter_device *const counter)
112 {
113 	if (!counter)
114 		return;
115 
116 	cdev_device_del(&counter->chrdev, &counter->dev);
117 
118 	mutex_lock(&counter->ops_exist_lock);
119 
120 	counter->ops = NULL;
121 	wake_up(&counter->events_wait);
122 
123 	mutex_unlock(&counter->ops_exist_lock);
124 
125 	put_device(&counter->dev);
126 }
127 EXPORT_SYMBOL_GPL(counter_unregister);
128 
devm_counter_release(void * counter)129 static void devm_counter_release(void *counter)
130 {
131 	counter_unregister(counter);
132 }
133 
134 /**
135  * devm_counter_register - Resource-managed counter_register
136  * @dev:	device to allocate counter_device for
137  * @counter:	pointer to Counter to register
138  *
139  * Managed counter_register. The Counter registered with this function is
140  * automatically unregistered on driver detach. This function calls
141  * counter_register internally. Refer to that function for more information.
142  *
143  * RETURNS:
144  * 0 on success, negative error number on failure.
145  */
devm_counter_register(struct device * dev,struct counter_device * const counter)146 int devm_counter_register(struct device *dev,
147 			  struct counter_device *const counter)
148 {
149 	int err;
150 
151 	err = counter_register(counter);
152 	if (err < 0)
153 		return err;
154 
155 	return devm_add_action_or_reset(dev, devm_counter_release, counter);
156 }
157 EXPORT_SYMBOL_GPL(devm_counter_register);
158 
159 #define COUNTER_DEV_MAX 256
160 
counter_init(void)161 static int __init counter_init(void)
162 {
163 	int err;
164 
165 	err = bus_register(&counter_bus_type);
166 	if (err < 0)
167 		return err;
168 
169 	err = alloc_chrdev_region(&counter_devt, 0, COUNTER_DEV_MAX, "counter");
170 	if (err < 0)
171 		goto err_unregister_bus;
172 
173 	return 0;
174 
175 err_unregister_bus:
176 	bus_unregister(&counter_bus_type);
177 	return err;
178 }
179 
counter_exit(void)180 static void __exit counter_exit(void)
181 {
182 	unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX);
183 	bus_unregister(&counter_bus_type);
184 }
185 
186 subsys_initcall(counter_init);
187 module_exit(counter_exit);
188 
189 MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
190 MODULE_DESCRIPTION("Generic Counter interface");
191 MODULE_LICENSE("GPL v2");
192