#include <linux/module.h>
#include <linux/io.h>
#include <linux/pci.h>
#include <linux/kernel.h>

static unsigned long phys;
module_param(phys, ulong, 0);
static unsigned long size = PAGE_SIZE;
module_param(size, ulong, 0);
static unsigned long newvec;
module_param(newvec, ulong, 0);
static unsigned long test_write;
module_param(test_write, ulong, 0);
static unsigned long entry_nr = ~0UL;
module_param(entry_nr, ulong, 0);

#define PCI_MSIX_ENTRY_SIZE 16

static void __iomem *test_setup(unsigned long phys_addr, unsigned long size)
{
    void __iomem *result;

    phys_addr = (phys_addr + PAGE_SIZE - 1) &  PAGE_MASK;

    size = (size + PAGE_SIZE -1 ) & PAGE_MASK;

    result = ioremap_nocache(phys_addr, size);

    if (!result)
        printk("ioremap for %lx %lx failed\n", phys_addr, size);

    return result;
}

static int read_vector(void * base, int entry_num)
{
    void __iomem *p;
    uint32_t val, i;

    p = base + entry_num * PCI_MSIX_ENTRY_SIZE;
    for (i = 0; i < 4; i ++)
    {
        val = readl(p);
        printk(" p %p val %x\n", p, val);
        p += 4;
    }

    return val;
}

static void write_vector(void *base, int entry_num, int new_vector)
{
    void __iomem *p;
    uint32_t val;

    p = base + entry_num * PCI_MSIX_ENTRY_SIZE + 8;

    val = readl(p);
    printk("p %p val %x\n", p, val);

    val &= ~0xff;
    val |= (new_vector | ~0xff);

    writel(val, p);

    printk("Now write finished\n");
}


static int __init ro_msi_init(void)
{
    void __iomem * vaddr;

    if (!phys || (entry_nr == ~0UL))
    {
        printk("No physical address or entry number specified\n");
        return -EINVAL;
    }

    if (test_write && !newvec)
    {
        printk("new vector not specified for write test\n");
        return -EINVAL;
    }
    printk("ro_msi init\n");
    vaddr = test_setup(phys, size);
    if (!vaddr)
    {
        printk("Failed to setup the iomap\n");
        return -EINVAL;
    }

    read_vector(vaddr, entry_nr);

    if (test_write)
        write_vector(vaddr, entry_nr, newvec);

    iounmap(vaddr);

    return 0;
}

static void __exit ro_msi_exit(void)
{
    printk("ro msi exit\n");
}
module_init(ro_msi_init);
module_exit(ro_msi_exit);