dev pci min works, non pci dev doesnt

kernel_module/hw_min.c

@@ -0,0 +1,75 @@
+/*
+TODO: how to setup a device with magic addresses without PCI?
+https://stackoverflow.com/questions/26965239/board-files-for-x86-based-systems
+
+request_mem_region returns NULL.
+
+TODO: which physical address is QEMU mapping?
+*/
+
+#include <asm/uaccess.h>
+#include <linux/cdev.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <uapi/linux/stat.h> /* S_IRUSR | S_IWUSR */
+
+#define CDEV_NAME "lkmc_hw_min"
+#define MMIO_LEN 8
+#define IRQ_RAISE 0
+#define IRQ_ACK 4
+
+MODULE_LICENSE("GPL");
+
+static unsigned long mmio_addr = 0;
+module_param(mmio_addr, ulong, S_IRUSR | S_IWUSR);
+
+static int major;
+static int irq;
+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 + IRQ_ACK);
+	return IRQ_HANDLED;
+}
+
+static int myinit(void)
+{
+	pr_info("init\n");
+	major = register_chrdev(0, CDEV_NAME, &fops);
+	mmio = (void __iomem *)mmio_addr;
+	if (request_mem_region(mmio_addr, MMIO_LEN, CDEV_NAME) == NULL) {
+		pr_info("request_mem_region\n");
+		goto error;
+	}
+	ioremap(mmio_addr, 8);
+	irq = 10;
+	if (request_irq(irq, irq_handler, IRQF_SHARED, CDEV_NAME, &major) < 0) {
+		pr_info("request_irq\n");
+		goto error;
+	}
+	iowrite32(0x12345678, mmio + IRQ_RAISE);
+	return 0;
+error:
+	return -ENODEV;
+}
+
+static void myexit(void)
+{
+	pr_info("exit\n");
+	free_irq(irq, &major);
+	release_mem_region(mmio_addr, MMIO_LEN);
+	unregister_chrdev(major, CDEV_NAME);
+}
+
+module_init(myinit);
+module_exit(myexit);

kernel_module/hw_pci_min.c

@@ -0,0 +1,90 @@
+#include <asm/uaccess.h>
+#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>
+
+#define BAR 0
+#define CDEV_NAME "lkmc_hw_pci_min"
+#define EDU_DEVICE_ID 0x11e9
+#define QEMU_VENDOR_ID 0x1234
+
+MODULE_LICENSE("GPL");
+
+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);

kernel_module/pci.c

@@ -242,6 +242,7 @@ static int pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
 		pr_info("irq %x\n", pci_irq);
 
 		/* Initial value of the IO memory. */
+        pr_info("mmio %p %llx\n", mmio, (unsigned long long)virt_to_phys(mmio));
 		for (i = 0; i < 0x28; i += 4) {
 			pr_info("io %x %x\n", i, ioread32((void*)(mmio + i)));
 		}

runqemu

@@ -53,6 +53,8 @@ case "$arch" in
         -M pc \
         -append 'root=/dev/vda $extra_append' \
         -device edu \
+        -device lkmc_min \
+        -device lkmc_pci_min \
         -drive file=${images_dir}/rootfs.ext2,if=virtio,format=raw \
         -kernel ${images_dir}/bzImage \
         -monitor telnet::45454,server,nowait \