#include <linux/module.h>
#include <linux/init.h>
#include <linux/spi/spi.h>

#define BUS_NUM     0

static struct spi_device* adxl345_dev = NULL;

/**
 * @brief This function is called, when the module is loaded into the kernel
 */
static int __init ModuleInit(void)
{
    struct spi_master* master = NULL;
    u8 id;

    /* Parameters for SPI device */
    struct spi_board_info spi_device_info = {
        .modalias = "adxl345",
        .max_speed_hz = 5000000,    /* Mhz */
        .bus_num = BUS_NUM,
        .chip_select = 0,
        .mode = 3,
    };

    /* Get access to spi bus */
    master = spi_busnum_to_master(BUS_NUM);

    /* Check if we could get the master */
    if (master == NULL)
    {
        printk("There is no spi bus with Nr. %d\n", BUS_NUM);
        return -1;
    }

    /* Create new SPI device.
    instantiate one new SPI device.
    defined - include/linux/spi.spi.h */
    adxl345_dev = spi_new_device(master, &spi_device_info);
    if (adxl345_dev == NULL)
    {
        printk("Could not create device!\n");
        return -1;
    }

    adxl345_dev->bits_per_word = 8;

    /* Setup the bus for device's parameters.
    Setup SPI mode and clock rate
    defined - include/linux/spi/spi.h */
    if (spi_setup(adxl345_dev) != 0)
    {
        printk("Could not change bus setup!\n");
        spi_unregister_device(adxl345_dev);
        return -1;
    }

    /* Read Chip ID */
    id = spi_w8r8(adxl345_dev, 0x00);
    printk("Chip ID: 0x%x\n", id);

    return 0;
}

/**
 * @brief This function is called, when the module is removed from the kernel
 */
static void __exit ModuleExit(void)
{
    if (adxl345_dev)
        spi_unregister_device(adxl345_dev);
}

module_init(ModuleInit);
module_exit(ModuleExit);

/* Meta Information */
MODULE_AUTHOR("Jura");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("A driver for reading out ID ADXL345 Accelerometer");