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// SPDX-License-Identifier: GPL-2.0
/*
* Generic Counter interface
* Copyright (C) 2020 William Breathitt Gray
*/
#include <linux/cdev.h>
#include <linux/counter.h>
#include <linux/device.h>
#include <linux/device/bus.h>
#include <linux/export.h>
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/idr.h>
#include <linux/init.h>
#include <linux/kdev_t.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/wait.h>
#include "counter-chrdev.h"
#include "counter-sysfs.h"
#define COUNTER_NAME "counter"
/* Provides a unique ID for each counter device */
static DEFINE_IDA(counter_ida);
struct counter_device_allochelper {
struct counter_device counter;
/*
* This ensures private data behaves like if it were kmalloced
* separately. Also ensures the minimum alignment for safe DMA
* operations (which may or may not mean cache alignment).
*/
unsigned long privdata[] __aligned(ARCH_DMA_MINALIGN);
};
static void counter_device_release(struct device *dev)
{
struct counter_device *const counter =
container_of(dev, struct counter_device, dev);
counter_chrdev_remove(counter);
ida_free(&counter_ida, dev->id);
kfree(container_of(counter, struct counter_device_allochelper, counter));
}
static struct device_type counter_device_type = {
.name = "counter_device",
.release = counter_device_release,
};
static struct bus_type counter_bus_type = {
.name = "counter",
.dev_name = "counter",
};
static dev_t counter_devt;
/**
* counter_priv - access counter device private data
* @counter: counter device
*
* Get the counter device private data
*/
void *counter_priv(const struct counter_device *const counter)
{
struct counter_device_allochelper *ch =
container_of(counter, struct counter_device_allochelper, counter);
return &ch->privdata;
}
EXPORT_SYMBOL_NS_GPL(counter_priv, COUNTER);
/**
* counter_alloc - allocate a counter_device
* @sizeof_priv: size of the driver private data
*
* This is part one of counter registration. The structure is allocated
* dynamically to ensure the right lifetime for the embedded struct device.
*
* If this succeeds, call counter_put() to get rid of the counter_device again.
*/
struct counter_device *counter_alloc(size_t sizeof_priv)
{
struct counter_device_allochelper *ch;
struct counter_device *counter;
struct device *dev;
int err;
ch = kzalloc(sizeof(*ch) + sizeof_priv, GFP_KERNEL);
if (!ch)
return NULL;
counter = &ch->counter;
dev = &counter->dev;
/* Acquire unique ID */
err = ida_alloc(&counter_ida, GFP_KERNEL);
if (err < 0)
goto err_ida_alloc;
dev->id = err;
mutex_init(&counter->ops_exist_lock);
dev->type = &counter_device_type;
dev->bus = &counter_bus_type;
dev->devt = MKDEV(MAJOR(counter_devt), dev->id);
err = counter_chrdev_add(counter);
if (err < 0)
goto err_chrdev_add;
device_initialize(dev);
err = dev_set_name(dev, COUNTER_NAME "%d", dev->id);
if (err)
goto err_dev_set_name;
return counter;
err_dev_set_name:
counter_chrdev_remove(counter);
err_chrdev_add:
ida_free(&counter_ida, dev->id);
err_ida_alloc:
kfree(ch);
return NULL;
}
EXPORT_SYMBOL_NS_GPL(counter_alloc, COUNTER);
void counter_put(struct counter_device *counter)
{
put_device(&counter->dev);
}
EXPORT_SYMBOL_NS_GPL(counter_put, COUNTER);
/**
* counter_add - complete registration of a counter
* @counter: the counter to add
*
* This is part two of counter registration.
*
* If this succeeds, call counter_unregister() to get rid of the counter_device again.
*/
int counter_add(struct counter_device *counter)
{
int err;
struct device *dev = &counter->dev;
if (counter->parent) {
dev->parent = counter->parent;
dev->of_node = counter->parent->of_node;
}
err = counter_sysfs_add(counter);
if (err < 0)
return err;
/* implies device_add(dev) */
return cdev_device_add(&counter->chrdev, dev);
}
EXPORT_SYMBOL_NS_GPL(counter_add, COUNTER);
/**
* counter_unregister - unregister Counter from the system
* @counter: pointer to Counter to unregister
*
* The Counter is unregistered from the system.
*/
void counter_unregister(struct counter_device *const counter)
{
if (!counter)
return;
cdev_device_del(&counter->chrdev, &counter->dev);
mutex_lock(&counter->ops_exist_lock);
counter->ops = NULL;
wake_up(&counter->events_wait);
mutex_unlock(&counter->ops_exist_lock);
}
EXPORT_SYMBOL_NS_GPL(counter_unregister, COUNTER);
static void devm_counter_release(void *counter)
{
counter_unregister(counter);
}
static void devm_counter_put(void *counter)
{
counter_put(counter);
}
/**
* devm_counter_alloc - allocate a counter_device
* @dev: the device to register the release callback for
* @sizeof_priv: size of the driver private data
*
* This is the device managed version of counter_add(). It registers a cleanup
* callback to care for calling counter_put().
*/
struct counter_device *devm_counter_alloc(struct device *dev, size_t sizeof_priv)
{
struct counter_device *counter;
int err;
counter = counter_alloc(sizeof_priv);
if (!counter)
return NULL;
err = devm_add_action_or_reset(dev, devm_counter_put, counter);
if (err < 0)
return NULL;
return counter;
}
EXPORT_SYMBOL_NS_GPL(devm_counter_alloc, COUNTER);
/**
* devm_counter_add - complete registration of a counter
* @dev: the device to register the release callback for
* @counter: the counter to add
*
* This is the device managed version of counter_add(). It registers a cleanup
* callback to care for calling counter_unregister().
*/
int devm_counter_add(struct device *dev,
struct counter_device *const counter)
{
int err;
err = counter_add(counter);
if (err < 0)
return err;
return devm_add_action_or_reset(dev, devm_counter_release, counter);
}
EXPORT_SYMBOL_NS_GPL(devm_counter_add, COUNTER);
#define COUNTER_DEV_MAX 256
static int __init counter_init(void)
{
int err;
err = bus_register(&counter_bus_type);
if (err < 0)
return err;
err = alloc_chrdev_region(&counter_devt, 0, COUNTER_DEV_MAX,
COUNTER_NAME);
if (err < 0)
goto err_unregister_bus;
return 0;
err_unregister_bus:
bus_unregister(&counter_bus_type);
return err;
}
static void __exit counter_exit(void)
{
unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX);
bus_unregister(&counter_bus_type);
}
subsys_initcall(counter_init);
module_exit(counter_exit);
MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
MODULE_DESCRIPTION("Generic Counter interface");
MODULE_LICENSE("GPL v2");