drivers/counter/counter-core.c

   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");