#include <linux/kernel.h>
#include <linux/module.h>
#include <asm/uaccess.h>    /* Needed for copy_from_user */
#include <asm/io.h>         /* Needed for IO Read/Write Functions */
#include <linux/proc_fs.h> /* Needed for Proc File System Functions */
#include <linux/seq_file.h> /* Needed for Sequence File Operations */

#include <linux/platform_device.h>  /* Needed for Platform Driver Functions */

/* Define Driver Name */
#define DRIVER_NAME "myled"

unsigned long *base_addr;   /* Vitual Base Address */
struct resource *res;       /* Device Resource Structure */
unsigned long remap_size; /* Device Memory Size */

/* Write operation for /proc/myled
 * -----------------------------------
 * When user cat a string to /proc/myled file, the string will be stored in
 * const char __user *buf. This function will copy the string from user
 * space into kernel space, and change it to an unsigned long value. 
 * It willn write the value to the register of myled controller,
 * and turn on the corresponding LEDs eventually.
 */
static ssize_t proc_myled_write(struct file *file, const char __user * buf,
				size_t count, loff_t * ppos)
{
  char myled_phrase[16];
  u32 myled_value;
  if (count < 11) {
    if (copy_from_user(myled_phrase, buf, count))
      return -EFAULT;
    myled_phrase[count] = '\0';
  }
  myled_value = simple_strtoul(myled_phrase, NULL, 0);
  wmb();
  iowrite32(myled_value, base_addr);
  return count;
}

/* Callback function when opening file /proc/myled
 * ------------------------------------------------------
 * Read the register value of myled controller, print the value to
 * the sequence file struct seq_file *p. In file open operation for /proc/myled
 * this callback function will be called first to fill up the seq_file,
 * and seq_read function will print whatever in seq_file to the terminal.
 */
static int proc_myled_show(struct seq_file *p, void *v)
{
  u32 myled_value;
  myled_value = ioread32(base_addr);
  seq_printf(p, "0x%x", myled_value);
  return 0;
}

/* Open function for /proc/myled
 * ------------------------------------
 * When user want to read /proc/myled (i.e. cat /proc/myled), the open function
 * will be called first. In the open function, a seq_file will be prepared and the
 * status of myled will be filled into the seq_file by proc_myled_show function.
 */
static int proc_myled_open(struct inode *inode, struct file *file)
{
  unsigned int size = 16;
  char *buf;
  struct seq_file *m;
  int res;
  buf = (char *)kmalloc(size * sizeof(char), GFP_KERNEL);
  if (!buf)
    return -ENOMEM;
  res = single_open(file, proc_myled_show, NULL);
  if (!res) {
    m = file->private_data;
    m->buf = buf;
    m->size = size;
  } else {
    kfree(buf);
  }
  return res;
}

/* File Operations for /proc/myled */
static const struct file_operations proc_myled_operations = {
  .open = proc_myled_open,
  .read = seq_read,
  .write = proc_myled_write,
  .llseek = seq_lseek,
  .release = single_release
};

/* Shutdown function for myled
 * -----------------------------------
 *  Before myled shutdown, turn-off all the leds
 */
static void myled_shutdown(struct platform_device *pdev)
{
  iowrite32(0, base_addr);
}

/* Remove function for myled
 * ----------------------------------
 *  When myled module is removed, turn off all the leds first,
 *  release virtual address and the memory region requested.
 */
static int myled_remove(struct platform_device *pdev)
{
  myled_shutdown(pdev);

  /* Remove /proc/myled entry */
  remove_proc_entry(DRIVER_NAME, NULL);

  /* Release mapped virtual address */
  iounmap(base_addr);
  
  /* Release the region */
  release_mem_region(res->start, remap_size);
  
  return 0;
}

/* Device Probe function for myled
 * ------------------------------------
 * Get the resource structure from the information in device tree.
 * request the memory regioon needed for the controller, and map it into
 * kernel virtual memory space. Create an entry under /proc file system
 * and register file operations for that entry.
 */
static int __devinit myled_probe(struct platform_device *pdev)
{
  struct proc_dir_entry *myled_proc_entry;
  int ret = 0;

  res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  if(!res){
    dev_err(&pdev->dev, "No memory resource\n");
    return -ENODEV;
  }

  remap_size = res->end - res->start + 1;
  if(!request_mem_region(res->start, remap_size, pdev->name)){
    dev_err(&pdev->dev, "Cannot request IO\n");
    return -ENXIO;
  }

  base_addr = ioremap(res->start, remap_size);
  if(base_addr == NULL){
    dev_err(&pdev->dev, "Couldn't ioremap memory at 0x%08lx\n", (unsigned long)res->start);
    ret = -ENOMEM;
    goto err_release_region;
  }

  myled_proc_entry = proc_create(DRIVER_NAME, 0, NULL,
				 &proc_myled_operations);
  if (myled_proc_entry == NULL) {
    dev_err(&pdev->dev, "Couldn't create proc entry\n");
    ret = -ENOMEM;
    goto err_create_proc_entry;
  }

  printk(KERN_INFO DRIVER_NAME " probed at VA 0x%08lx\n", (unsigned long) base_addr);

  return 0;
  
 err_create_proc_entry:
  iounmap(base_addr);

 err_release_region:
  release_mem_region(res->start, remap_size);

  return ret;
}

/* device match table to match with device node in device tree */
static const struct of_device_id myled_of_match[] __devinitconst = {
  {.compatible = "dglnt,myled-1.00.a"},
  {},
};

MODULE_DEVICE_TABLE(of, myled_of_match);

/* platform driver structure for myled driver */
static struct platform_driver myled_driver = {
  .driver = {
    .name = DRIVER_NAME,
    .owner = THIS_MODULE,
    .of_match_table = myled_of_match},
  .probe = myled_probe,
  .remove = __devexit_p(myled_remove),
  .shutdown = __devexit_p(myled_shutdown)
};

/* Register myled platform driver */
module_platform_driver(myled_driver);

/* Module Infomations */
MODULE_AUTHOR("Digilent, Inc.");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION(DRIVER_NAME ": MYLED driver (Simple Version)");
MODULE_ALIAS(DRIVER_NAME);