SRAM Map to files driver

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/version.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/kdev_t.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/cdev.h>
#include <linux/uaccess.h>
#include <asm/io.h>

#define MAXDEVICES 4
//#define GETSTARTADDR(x, y) start_addr_b ## x ## _c ## y
static int start_addr_b1c1 = 0x3F000000;
static int start_addr_b1c2 = 0x3F002000;
static int start_addr_b2c1 = 0x3F004000;
static int start_addr_b2c2 = 0x3F006000;
static int FMRAM_BASE = 0x3F000000;
static int FMRAM_SIZE = 0x00002000; /* 8k bytes */
static char* dev_names[] = {"_B1C1", "_B1C2", "_B2C1", "_B2C2"};

module_param(start_addr_b1c1, int, 0644);
MODULE_PARM_DESC(start_addr, "Starting Address, buffer 1 channel 1");
module_param(start_addr_b1c2, int, 0644);
MODULE_PARM_DESC(start_addr, "Starting Address, buffer 1 channel 2");
module_param(start_addr_b2c1, int, 0644);
MODULE_PARM_DESC(start_addr, "Starting Address, buffer 2 channel 1");
module_param(start_addr_b2c2, int, 0644);
MODULE_PARM_DESC(start_addr, "Starting Address, buffer 2 channel 2");
module_param_named(data_size, FMRAM_SIZE, int, 0644);
MODULE_PARM_DESC(data_size, "Size of data, channel 2");

static void __iomem *fmram;
static dev_t first;
static struct cdev c_dev;
static struct class *cl;

static int my_open(struct inode *i, struct file *f)
{
    int minor = MINOR(i->i_rdev);
    printk("minor = %d", minor);
    switch (minor)
    {
        case 0: FMRAM_BASE = start_addr_b1c1; break;
        case 1: FMRAM_BASE = start_addr_b1c2; break;
        case 2: FMRAM_BASE = start_addr_b2c1; break;
        case 3: FMRAM_BASE = start_addr_b2c2; break;
        default: printk(KERN_ERR "Invalid device minor: %d\n", minor);
    }
    if ((fmram = ioremap(FMRAM_BASE, FMRAM_SIZE)) == NULL)
    {
        printk(KERN_ERR "Mapping FM RAM memory failed\n");
        return -1;
    }
    return 0;
}

static int my_close(struct inode *i, struct file *f)
{
    iounmap(fmram);
    return 0;
}

static ssize_t my_read(struct file *f, char __user *buf, size_t len, loff_t *off)
{
    int i;
    u8 byte;

    if (*off >= FMRAM_SIZE)
    {
        return 0;
    }
    if (*off + len > FMRAM_SIZE)
    {
        len = FMRAM_SIZE - *off;
    }
    for (i = 0; i < len; i++)
    {
        byte = ioread8((u8 *)fmram + *off + i);
        if (copy_to_user(buf + i, &byte, 1))
        {
            return -EFAULT;
        }
    }
    *off += len;

    return len;
}

static ssize_t my_write(struct file *f, const char __user *buf, size_t len, loff_t *off)
{
    int i;
    u8 byte;

    if (*off >= FMRAM_SIZE)
    {
        return 0;
    }
    if (*off + len > FMRAM_SIZE)
    {
        len = FMRAM_SIZE - *off;
    }
    for (i = 0; i < len; i++)
    {
        if (copy_from_user(&byte, buf + i, 1))
        {
            return -EFAULT;
        }
        iowrite8(byte, (u8 *)fmram + *off + i);
    }
    *off += len;

    return len;
}

static struct file_operations fmram_fops =
{
    .owner = THIS_MODULE,
    .open = my_open,
    .release = my_close,
    .read = my_read,
    .write = my_write
};

static int __init fmram_init(void) /* Constructor */
{

    int i, rc = 0;
    if (alloc_chrdev_region(&first, 0, MAXDEVICES, "fmram") < 0)
    {
        return -1;
    }
    if ((cl = class_create(THIS_MODULE, "chardrv")) == NULL)
    {
        unregister_chrdev_region(first, 1);
        return -1;
    }

    cdev_init(&c_dev, &fmram_fops);
    if (cdev_add(&c_dev, first, 1) == -1)
    {
            device_destroy(cl, first);
            class_destroy(cl);
            unregister_chrdev_region(first, 1);

    }
    for (i= 0; i< 4; i++)
    {
        if (device_create(cl, NULL, MKDEV(MAJOR(first), MINOR(first)+i), NULL, "fmram%s",
                    dev_names[i]) == NULL)
        {
            rc = -1;
            break;
        }


    }
    if (rc < 0)
    {
        class_destroy(cl);
        unregister_chrdev_region(first, 1);
        return -1;
    }

    return 0;
}

static void __exit fmram_exit(void) /* Destructor */
{
    int i;
    cdev_del(&c_dev);
    for(i = 0; i< 4; i++)
        device_destroy(cl, MKDEV(first, i));
    class_destroy(cl);
    unregister_chrdev_region(first, 1);
}

module_init(fmram_init);
module_exit(fmram_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Prateek Sharma (b48601)");
MODULE_DESCRIPTION("FM RAM Driver");