Understanding Linux driver

I will like to understand how this driver works , can anyone put comments or send me to a site that would explain most of this commands

#include <linux/miscdevice.h>
#include <linux/delay.h>
#include <asm/irq.h>
#include <mach/regs-gpio.h>
#include <mach/hardware.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/ioctl.h>
#include <linux/cdev.h>
#include <linux/string.h>
#include <linux/list.h>
#include <linux/pci.h>
#include <linux/gpio.h>
#include <asm/uaccess.h>
#include <asm/atomic.h>
#include <asm/unistd.h>


#define DEVICE_NAME "leds"

static unsigned long led_table [] = {
  S3C2410_GPB(5),
  S3C2410_GPB(6),
  S3C2410_GPB(7),
  S3C2410_GPB(8),
};

static unsigned int led_cfg_table [] = {
  S3C2410_GPIO_OUTPUT,
  S3C2410_GPIO_OUTPUT,
  S3C2410_GPIO_OUTPUT,
  S3C2410_GPIO_OUTPUT,
};

static int sbc2440_leds_ioctl(
  struct inode *inode, 
  struct file *file, 
  unsigned int cmd, 
  unsigned long arg)
{
  switch(cmd) {
  case 0:
  case 1:
    if (arg > 4) {
      return -EINVAL;
    }
    s3c2410_gpio_setpin(led_table[arg], !cmd);
    return 0;
  default:
    return -EINVAL;
  }
}

static struct file_operations dev_fops = {
  .owner  =  THIS_MODULE,
  .ioctl  =  sbc2440_leds_ioctl,
};

static struct miscdevice misc = {
  .minor = MISC_DYNAMIC_MINOR,
  .name = DEVICE_NAME,
  .fops = &dev_fops,
};

static int __init dev_init(void)
{
  int ret;

  int i;
  
  for (i = 0; i < 4; i++) {
    s3c2410_gpio_cfgpin(led_table[i], led_cfg_table[i]);
    s3c2410_gpio_setpin(led_table[i], 0);
  }

  ret = misc_register(&misc);

  printk (DEVICE_NAME"\tinitialized\n");

  return ret;
}

static void __exit dev_exit(void)
{
  misc_deregister(&misc);
}

module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("FriendlyARM Inc.");

See Linux Device Drivers, 3rd Edition.

--- rod

Originally Posted by theNbomr See Linux Device Drivers, 3rd Edition. --- rod

I did and it does not talk about GPIO

i am beginner for fedro15 and how to install rtlinux and use modules

GPIO is generally very platform-specific. It should be documented by your hardware vendor.

--- rod.

Originally Posted by theNbomr GPIO is generally very platform-specific. It should be documented by your hardware vendor. --- rod.

no is not, you can activate the GPIO in the kernel and use command like:

echo "1" > gpio32/value
echo "0" > gpio32/value

to turn on and off an led on the GPIO line.

Originally Posted by icemetal no is not, you can activate the GPIO in the kernel and use command like: echo "1" > gpio32/value echo "0" > gpio32/value to turn on and off an led on the GPIO line.

In fact - it is platform specific (although GPIO is very similar, like a standard in most HW implementations, only specific / small details would differ) but this is why you have drivers.

Above code seems to be a driver to interact with LEDs connected to some of SoC gpio pins.

static int sbc2440_leds_ioctl(
  struct inode *inode, 
  struct file *file, 
  unsigned int cmd, 
  unsigned long arg)

is the implementation of a code that turns on or of (depending on cmd being true or false) an LED indexed by 'arg'.

static int __init dev_init(void)

is used to turn them of on a module load (init) and to set up a configuration*.
(configuration of GPIO pins that these LEDs are connected to - GPIOs can be configured to be either input (if used e.g. for switches / buttons etc) or as OUTPUT (if used to control something, e.g. an LED).

I figure how that driver works, but that driver is very limited to that chip, so I enable the standard gpio libraries in linux, so my c code would work in any ARM32 processor that has linux in it(with the gpio in the kernel enable), I found this couple of pages very useful, but thanks formiaczek for taking the time to explain that part of the code.

http://blog.makezine.com/archive/200...gle-board.html

http://www.avrfreaks.net/wiki/index....ion:Linux/GPIO