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 /* Provides a unique ID for each counter device */
  26 static DEFINE_IDA(counter_ida);
  27
  28 struct counter_device_allochelper {
  29         struct counter_device counter;
  30
  31         /*
  32          * This is cache line aligned to ensure private data behaves like if it
  33          * were kmalloced separately.
  34          */
  35         unsigned long privdata[] ____cacheline_aligned;
  36 };
  37
  38 static void counter_device_release(struct device *dev)
  39 {
  40         struct counter_device *const counter =
  41                 container_of(dev, struct counter_device, dev);
  42
  43         counter_chrdev_remove(counter);
  44         ida_free(&counter_ida, dev->id);
  45
  46         kfree(container_of(counter, struct counter_device_allochelper, counter));
  47 }
  48
  49 static struct device_type counter_device_type = {
  50         .name = "counter_device",
  51         .release = counter_device_release,
  52 };
  53
  54 static struct bus_type counter_bus_type = {
  55         .name = "counter",
  56         .dev_name = "counter",
  57 };
  58
  59 static dev_t counter_devt;
  60
  61 /**
  62  * counter_priv - access counter device private data
  63  * @counter: counter device
  64  *
  65  * Get the counter device private data
  66  */
  67 void *counter_priv(const struct counter_device *const counter)
  68 {
  69         struct counter_device_allochelper *ch =
  70                 container_of(counter, struct counter_device_allochelper, counter);
  71
  72         return &ch->privdata;
  73 }
  74 EXPORT_SYMBOL_GPL(counter_priv);
  75
  76 /**
  77  * counter_alloc - allocate a counter_device
  78  * @sizeof_priv: size of the driver private data
  79  *
  80  * This is part one of counter registration. The structure is allocated
  81  * dynamically to ensure the right lifetime for the embedded struct device.
  82  *
  83  * If this succeeds, call counter_put() to get rid of the counter_device again.
  84  */
  85 struct counter_device *counter_alloc(size_t sizeof_priv)
  86 {
  87         struct counter_device_allochelper *ch;
  88         struct counter_device *counter;
  89         struct device *dev;
  90         int err;
  91
  92         ch = kzalloc(sizeof(*ch) + sizeof_priv, GFP_KERNEL);
  93         if (!ch)
  94                 return NULL;
  95
  96         counter = &ch->counter;
  97         dev = &counter->dev;
  98
  99         /* Acquire unique ID */
 100         err = ida_alloc(&counter_ida, GFP_KERNEL);
 101         if (err < 0)
 102                 goto err_ida_alloc;
 103         dev->id = err;
 104
 105         mutex_init(&counter->ops_exist_lock);
 106         dev->type = &counter_device_type;
 107         dev->bus = &counter_bus_type;
 108         dev->devt = MKDEV(MAJOR(counter_devt), dev->id);
 109
 110         err = counter_chrdev_add(counter);
 111         if (err < 0)
 112                 goto err_chrdev_add;
 113
 114         device_initialize(dev);
 115
 116         return counter;
 117
 118 err_chrdev_add:
 119
 120         ida_free(&counter_ida, dev->id);
 121 err_ida_alloc:
 122
 123         kfree(ch);
 124
 125         return NULL;
 126 }
 127 EXPORT_SYMBOL_GPL(counter_alloc);
 128
 129 void counter_put(struct counter_device *counter)
 130 {
 131         put_device(&counter->dev);
 132 }
 133 EXPORT_SYMBOL_GPL(counter_put);
 134
 135 /**
 136  * counter_add - complete registration of a counter
 137  * @counter: the counter to add
 138  *
 139  * This is part two of counter registration.
 140  *
 141  * If this succeeds, call counter_unregister() to get rid of the counter_device again.
 142  */
 143 int counter_add(struct counter_device *counter)
 144 {
 145         int err;
 146         struct device *dev = &counter->dev;
 147
 148         if (counter->parent) {
 149                 dev->parent = counter->parent;
 150                 dev->of_node = counter->parent->of_node;
 151         }
 152
 153         err = counter_sysfs_add(counter);
 154         if (err < 0)
 155                 return err;
 156
 157         /* implies device_add(dev) */
 158         return cdev_device_add(&counter->chrdev, dev);
 159 }
 160 EXPORT_SYMBOL_GPL(counter_add);
 161
 162 /**
 163  * counter_unregister - unregister Counter from the system
 164  * @counter:    pointer to Counter to unregister
 165  *
 166  * The Counter is unregistered from the system.
 167  */
 168 void counter_unregister(struct counter_device *const counter)
 169 {
 170         if (!counter)
 171                 return;
 172
 173         cdev_device_del(&counter->chrdev, &counter->dev);
 174
 175         mutex_lock(&counter->ops_exist_lock);
 176
 177         counter->ops = NULL;
 178         wake_up(&counter->events_wait);
 179
 180         mutex_unlock(&counter->ops_exist_lock);
 181 }
 182 EXPORT_SYMBOL_GPL(counter_unregister);
 183
 184 static void devm_counter_release(void *counter)
 185 {
 186         counter_unregister(counter);
 187 }
 188
 189 static void devm_counter_put(void *counter)
 190 {
 191         counter_put(counter);
 192 }
 193
 194 /**
 195  * devm_counter_alloc - allocate a counter_device
 196  * @dev: the device to register the release callback for
 197  * @sizeof_priv: size of the driver private data
 198  *
 199  * This is the device managed version of counter_add(). It registers a cleanup
 200  * callback to care for calling counter_put().
 201  */
 202 struct counter_device *devm_counter_alloc(struct device *dev, size_t sizeof_priv)
 203 {
 204         struct counter_device *counter;
 205         int err;
 206
 207         counter = counter_alloc(sizeof_priv);
 208         if (!counter)
 209                 return NULL;
 210
 211         err = devm_add_action_or_reset(dev, devm_counter_put, counter);
 212         if (err < 0)
 213                 return NULL;
 214
 215         return counter;
 216 }
 217 EXPORT_SYMBOL_GPL(devm_counter_alloc);
 218
 219 /**
 220  * devm_counter_add - complete registration of a counter
 221  * @dev: the device to register the release callback for
 222  * @counter: the counter to add
 223  *
 224  * This is the device managed version of counter_add(). It registers a cleanup
 225  * callback to care for calling counter_unregister().
 226  */
 227 int devm_counter_add(struct device *dev,
 228                      struct counter_device *const counter)
 229 {
 230         int err;
 231
 232         err = counter_add(counter);
 233         if (err < 0)
 234                 return err;
 235
 236         return devm_add_action_or_reset(dev, devm_counter_release, counter);
 237 }
 238 EXPORT_SYMBOL_GPL(devm_counter_add);
 239
 240 #define COUNTER_DEV_MAX 256
 241
 242 static int __init counter_init(void)
 243 {
 244         int err;
 245
 246         err = bus_register(&counter_bus_type);
 247         if (err < 0)
 248                 return err;
 249
 250         err = alloc_chrdev_region(&counter_devt, 0, COUNTER_DEV_MAX, "counter");
 251         if (err < 0)
 252                 goto err_unregister_bus;
 253
 254         return 0;
 255
 256 err_unregister_bus:
 257         bus_unregister(&counter_bus_type);
 258         return err;
 259 }
 260
 261 static void __exit counter_exit(void)
 262 {
 263         unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX);
 264         bus_unregister(&counter_bus_type);
 265 }
 266
 267 subsys_initcall(counter_init);
 268 module_exit(counter_exit);
 269
 270 MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
 271 MODULE_DESCRIPTION("Generic Counter interface");
 272 MODULE_LICENSE("GPL v2");