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                 err = -ENOMEM;
  95                 goto err_alloc_ch;
  96         }
  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         return counter;
 119
 120 err_chrdev_add:
 121
 122         ida_free(&counter_ida, dev->id);
 123 err_ida_alloc:
 124
 125         kfree(ch);
 126 err_alloc_ch:
 127
 128         return ERR_PTR(err);
 129 }
 130 EXPORT_SYMBOL_GPL(counter_alloc);
 131
 132 void counter_put(struct counter_device *counter)
 133 {
 134         put_device(&counter->dev);
 135 }
 136 EXPORT_SYMBOL_GPL(counter_put);
 137
 138 /**
 139  * counter_add - complete registration of a counter
 140  * @counter: the counter to add
 141  *
 142  * This is part two of counter registration.
 143  *
 144  * If this succeeds, call counter_unregister() to get rid of the counter_device again.
 145  */
 146 int counter_add(struct counter_device *counter)
 147 {
 148         int err;
 149         struct device *dev = &counter->dev;
 150
 151         if (counter->parent) {
 152                 dev->parent = counter->parent;
 153                 dev->of_node = counter->parent->of_node;
 154         }
 155
 156         err = counter_sysfs_add(counter);
 157         if (err < 0)
 158                 return err;
 159
 160         /* implies device_add(dev) */
 161         return cdev_device_add(&counter->chrdev, dev);
 162 }
 163 EXPORT_SYMBOL_GPL(counter_add);
 164
 165 /**
 166  * counter_unregister - unregister Counter from the system
 167  * @counter:    pointer to Counter to unregister
 168  *
 169  * The Counter is unregistered from the system.
 170  */
 171 void counter_unregister(struct counter_device *const counter)
 172 {
 173         if (!counter)
 174                 return;
 175
 176         cdev_device_del(&counter->chrdev, &counter->dev);
 177
 178         mutex_lock(&counter->ops_exist_lock);
 179
 180         counter->ops = NULL;
 181         wake_up(&counter->events_wait);
 182
 183         mutex_unlock(&counter->ops_exist_lock);
 184 }
 185 EXPORT_SYMBOL_GPL(counter_unregister);
 186
 187 static void devm_counter_release(void *counter)
 188 {
 189         counter_unregister(counter);
 190 }
 191
 192 static void devm_counter_put(void *counter)
 193 {
 194         counter_put(counter);
 195 }
 196
 197 /**
 198  * devm_counter_alloc - allocate a counter_device
 199  * @dev: the device to register the release callback for
 200  * @sizeof_priv: size of the driver private data
 201  *
 202  * This is the device managed version of counter_add(). It registers a cleanup
 203  * callback to care for calling counter_put().
 204  */
 205 struct counter_device *devm_counter_alloc(struct device *dev, size_t sizeof_priv)
 206 {
 207         struct counter_device *counter;
 208         int err;
 209
 210         counter = counter_alloc(sizeof_priv);
 211         if (IS_ERR(counter))
 212                 return counter;
 213
 214         err = devm_add_action_or_reset(dev, devm_counter_put, counter);
 215         if (err < 0)
 216                 return ERR_PTR(err);
 217
 218         return counter;
 219 }
 220 EXPORT_SYMBOL_GPL(devm_counter_alloc);
 221
 222 /**
 223  * devm_counter_add - complete registration of a counter
 224  * @dev: the device to register the release callback for
 225  * @counter: the counter to add
 226  *
 227  * This is the device managed version of counter_add(). It registers a cleanup
 228  * callback to care for calling counter_unregister().
 229  */
 230 int devm_counter_add(struct device *dev,
 231                      struct counter_device *const counter)
 232 {
 233         int err;
 234
 235         err = counter_add(counter);
 236         if (err < 0)
 237                 return err;
 238
 239         return devm_add_action_or_reset(dev, devm_counter_release, counter);
 240 }
 241 EXPORT_SYMBOL_GPL(devm_counter_add);
 242
 243 #define COUNTER_DEV_MAX 256
 244
 245 static int __init counter_init(void)
 246 {
 247         int err;
 248
 249         err = bus_register(&counter_bus_type);
 250         if (err < 0)
 251                 return err;
 252
 253         err = alloc_chrdev_region(&counter_devt, 0, COUNTER_DEV_MAX, "counter");
 254         if (err < 0)
 255                 goto err_unregister_bus;
 256
 257         return 0;
 258
 259 err_unregister_bus:
 260         bus_unregister(&counter_bus_type);
 261         return err;
 262 }
 263
 264 static void __exit counter_exit(void)
 265 {
 266         unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX);
 267         bus_unregister(&counter_bus_type);
 268 }
 269
 270 subsys_initcall(counter_init);
 271 module_exit(counter_exit);
 272
 273 MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
 274 MODULE_DESCRIPTION("Generic Counter interface");
 275 MODULE_LICENSE("GPL v2");