pci_min.c

/* https://cirosantilli.com/linux-kernel-module-cheat#pci-min */

#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/uaccess.h> /* copy_from_user, copy_to_user */

#define BAR 0
#define CDEV_NAME "lkmc_hw_pci_min"
#define EDU_DEVICE_ID 0x11e9
#define QEMU_VENDOR_ID 0x1234

static struct pci_device_id id_table[] = {
	{ PCI_DEVICE(QEMU_VENDOR_ID, EDU_DEVICE_ID), },
	{ 0, }
};
MODULE_DEVICE_TABLE(pci, id_table);
static int major;
static struct pci_dev *pdev;
static void __iomem *mmio;
static struct file_operations fops = {
	.owner   = THIS_MODULE,
};

static irqreturn_t irq_handler(int irq, void *dev)
{
	pr_info("irq_handler irq = %d dev = %d\n", irq, *(int *)dev);
	iowrite32(0, mmio + 4);
	return IRQ_HANDLED;
}

static int probe(struct pci_dev *dev, const struct pci_device_id *id)
{
	pr_info("probe\n");
	major = register_chrdev(0, CDEV_NAME, &fops);
	pdev = dev;
	if (pci_enable_device(dev) < 0) {
		dev_err(&(pdev->dev), "pci_enable_device\n");
		goto error;
	}
	if (pci_request_region(dev, BAR, "myregion0")) {
		dev_err(&(pdev->dev), "pci_request_region\n");
		goto error;
	}
	mmio = pci_iomap(pdev, BAR, pci_resource_len(pdev, BAR));
	pr_info("dev->irq = %u\n", dev->irq);
	if (request_irq(dev->irq, irq_handler, IRQF_SHARED, "pci_irq_handler0", &major) < 0) {
		dev_err(&(dev->dev), "request_irq\n");
		goto error;
	}
	iowrite32(0x12345678, mmio);
	return 0;
error:
	return 1;
}

static void remove(struct pci_dev *dev)
{
	pr_info("remove\n");
	free_irq(dev->irq, &major);
	pci_release_region(dev, BAR);
	unregister_chrdev(major, CDEV_NAME);
}

static struct pci_driver pci_driver = {
	.name     = CDEV_NAME,
	.id_table = id_table,
	.probe    = probe,
	.remove   = remove,
};

static int myinit(void)
{
	if (pci_register_driver(&pci_driver) < 0) {
		return 1;
	}
	return 0;
}

static void myexit(void)
{
	pci_unregister_driver(&pci_driver);
}

module_init(myinit);
module_exit(myexit);
MODULE_LICENSE("GPL");