#include <linux/init.h>
#include <linux/module.h>
#include <linux/err.h>
#include <linux/timer.h>

//#include <asm/io.h>
//#include <mach/platform.h>
//#include <linux/device.h>

//#define __io_address(n)     IOMEM(IO_ADDRESS(n))
//#define IOMEM(x)  ((void __force __iomem *)(x))
//#define IOMEM(x)  (x)

#define IO_ADDRESS(x)               (((x) & 0x00ffffff) + (((x) >> 4) & 0x0f000000) + 0xf0000000)
#define BCM2708_PERI_BASE           0x3F000000

#define GPIO_OFFSET                 0x200000
#define GPIO_BASE                   (BCM2708_PERI_BASE + GPIO_OFFSET)


MODULE_LICENSE("GPL");

struct GpioRegisters
{
    uint32_t GPFSEL[6];
    uint32_t Reserved1;
    uint32_t GPSET[2];
    uint32_t Reserved2;
    uint32_t GPCLR[2];
};

struct GpioRegisters *s_pGpioRegisters;

static void SetGPIOFunction(int GPIO, int functionCode)
{
    int registerIndex = GPIO / 10;
    int bit = (GPIO % 10) * 3;

    unsigned oldValue = s_pGpioRegisters->GPFSEL[registerIndex];
    unsigned mask = 0b111 << bit;
    printk("Changing function of GPIO%d from %x to %x\n", GPIO, (oldValue >> bit) & 0b111, functionCode);
    s_pGpioRegisters->GPFSEL[registerIndex] = (oldValue & ~mask) | ((functionCode << bit) & mask);
}

static void SetGPIOOutputValue(int GPIO, bool outputValue)
{
    if (outputValue)
        s_pGpioRegisters->GPSET[GPIO / 32] = (1 << (GPIO % 32));
    else
        s_pGpioRegisters->GPCLR[GPIO / 32] = (1 << (GPIO % 32));
}

static struct timer_list s_BlinkTimer;
static int s_BlinkPeriod = 1000;
static const int LedGpioPin = 25;

static void BlinkTimerHandler(unsigned long unused)
{
    static bool on = false;
    on = !on;
    SetGPIOOutputValue(LedGpioPin, on);
    mod_timer(&s_BlinkTimer, jiffies + msecs_to_jiffies(s_BlinkPeriod));
}

static int __init LedBlinkModule_init(void)
{
    int result;
    unsigned int address;
    //address = IO_ADDRESS(GPIO_BASE);
    address = 0xF3200000;
    printk("address: %d\n", address);
    s_pGpioRegisters = (struct GpioRegisters *)address;

    SetGPIOFunction(LedGpioPin, 0b001); //Configure the pin as output

    setup_timer(&s_BlinkTimer, BlinkTimerHandler, 0);
    result = mod_timer(&s_BlinkTimer, jiffies + msecs_to_jiffies(s_BlinkPeriod));
    BUG_ON(result < 0);

    return 0;
}

static void __exit LedBlinkModule_exit(void)
{
    SetGPIOFunction(LedGpioPin, 0); //Configure the pin as input
    del_timer(&s_BlinkTimer);
}

module_init(LedBlinkModule_init);
module_exit(LedBlinkModule_exit);