uio_kbd.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * UIO demonstration driver catching keyboard events
 *
 * Copyright (C) 2024 Smile
 * Author: Antoine Bax de keating <antoine.baxdekeating@smile.eu>
 */

#include <linux/kernel.h>	/* printk() */
#include <linux/module.h>	/* modules */
#include <linux/init.h>		/* module_{init,exit}() */
#include <linux/uio_driver.h>
#include <linux/device.h>
#include <linux/slab.h> /* kzalloc */

MODULE_LICENSE("GPL");


/*
 * Global variables
 */
static const int irq = 1; // IRQ 1 is the keyboard IRQ on Intel architecture.
static struct uio_info *info;
static struct device *dev;
char *mem_area;

/*
 * Handlers
 */

static irqreturn_t uio_handler(int irq, struct uio_info *dev_info)
{
	static unsigned int irq_count;

	pr_info("UIO handler");

	irq_count++;
	memcpy(mem_area, &irq_count, sizeof(irq_count));

	return IRQ_HANDLED;
}

static void uio_release(struct device *dev)
{
	pr_info("UIO release\n");
}

/*
 * Init and Exit
 */
static int __init uio_kbd_init(void)
{
	int ret;

	dev = kzalloc(sizeof(struct device), GFP_KERNEL);
	dev_set_name(dev, "uio_kbd_device");
	dev->release = uio_release;
	ret = device_register(dev);
	if (ret < 0) {
		kfree(dev);
		pr_warn("Failing to register uio_kbd device\n");
		return ret;
	}



	mem_area = kzalloc(PAGE_SIZE, GFP_KERNEL);

	info = kzalloc(sizeof(struct uio_info), GFP_KERNEL);
	info->name = "uio_kbd_device";
	info->version = "0.0.1";
	info->irq = irq;
	info->irq_flags = IRQF_SHARED;
	info->handler = uio_handler;

	info->mem[0].name = "basic_mem_map";
	info->mem[0].memtype = UIO_MEM_LOGICAL;
	info->mem[0].addr = (phys_addr_t) mem_area;
	info->mem[0].size = PAGE_SIZE;

	ret = uio_register_device(dev, info);
	if (ret < 0) {
		device_unregister(dev);
		kfree(dev);
		kfree(info);
		kfree(mem_area);
		pr_warn("Failing to register uio_kbd UIO device\n");
		return ret;
	}

	pr_info("Registered UIO handler for IRQ=%d\n", irq);
	return 0;
}

static void __exit uio_kbd_exit(void)
{
	uio_unregister_device(info);
	device_unregister(dev);
	pr_info("Un-Registered UIO handler for IRQ=%d\n", irq);
	kfree(info);
	kfree(dev);
	kfree(mem_area);
}

module_init(uio_kbd_init);
module_exit(uio_kbd_exit);