LED: Control Light Emitting diode

1, LED drive realization principle,

2. Write LED Driver

(1) Create LED-driven device files

First step: Initialize the Cdev with the Cdev_init function

Step Two: Specify the device number

Step three: Use the Cdev_add function to add a character device to the character device array in the kernel

Fourth step: Create a struct class using the Class_create macro

Fifth step: Create a device file using the Device_create function

#define DEVICE_NAME "S3c6410_leds"//define Device file name

#define DEVICE_COUNT 1//number of created device files

#define S3C6410_LEDS_MAJOR 0//default main device number

#define S3c6410_leds_minor 234//default secondary device number

static int major = S3c6410_leds_major; Main device number

static int minor = S3c6410_leds_minor; Secondary device number

Static dev_t Dev_number; Device number

static struct Class *leds_class = NULL; struct class

static struct File_operations Dev_ops =

{

. Owner = This_modules,

. Unlocked_ioctl = S3c6410_leds_ioctl,

. write = S3c6410_leds_write

};

static struct Cdev Led_cdev; struct Cdev describing the character device

Create a device file

static int leds_create_device (void)

{

int ret = 0;

int err = 0;

Cdev_init (&leds_cdev, &dev_fops);

Leds_cdev.owner = This_modules;

if (Major > 0)

{

Dev_number = MKDEV (major, minor);

Err = Register_chrdev_region (Dev_number, Device_count, devoce_name);

if (Err < 0)

{

PRINTK (kern_warning "register_chrdev_region () failed\n");

return err;

}

}

Else

{

Err = Alloc_chrdev_region (&leds_cdev.dev, ten, Device_count, device_name);

if (Err < 0)

{

PRINTK (kern_warning "alloc_chrdev_region () failed\n");

return err;

}

Major = Major (Leds_cdev.dev);

Minor = minor (Leds_cdev.dev);

Dev_number = Leds_cev.dev;

}

ret = Cdev_add (&leds_cdev, Dev_number, Device_count);

Leds_class = Class_create (This_module, device_name);

Device_create (Leds_class, NULL, Dev_number, NULL, device_name);

return ret;

}

(2) LED driver initialization function

static int leds_init (void)

{

int ret;

ret = Leds_crerate_device ();

PRINTK (device_name "\tinitialized\n");

return ret;

}

Module_init (Leds_init);

(3) LED drive unload function

static void Leds_destroy_device (void)

{

Device_destory (Led_class, Dev_number); Remove the character device created by the Device_create function

if (Leds_class)//Destroy struct class

Class_destroy (Leds_class);

Unregister_chrdev_region (Dev_number, Device_number);

}

static void Leds_exit (void)

{

Leds_destroy_device ();

PRINTK (device_name "\texit!\n");

}

Module_exit (Leds_exit);

(4) Set register and initialize led driver

static int leds_state = 1;

static void leds_init_gpm (int leds_default)

{

Initialize S3c64xx_gpmcon

int tmp = 0;

TMP = IOREAD32 (S3c64xx_gpmcon);

TMP &= (~0XFFFF);

TMP |= 0x1111;

IOWRITE32 (TMP, S3c64xx_gpmcon);

Initialize S3c64xx_gpmpud

TMP = IOREAD32 (S3C64XX_GPMPUD);

TMP &= (~0XFF);

TMP |= 0xAA;

IOWRITE32 (TMP, S3C64XX_GPMPUD);

Initialize S3c64xx_gpmdat

TMP = IOREAD32 (S3c64xx_gpmdat);

TMP &= (~0XF);

TMP |= Leds_default;

IOWRITE32 (TMP, S3C64XX_GPMDAT);

}

static int leds_init (void)

{

int ret;

ret = Leds_create_device ();

LEDS_INIT_GPM (~leds_state);

return ret;

}

(5) Control LED

Controlling LEDs with strings

static unsigned char mem[4];

Static ssize_t s3c6410_leds_write (struct file *file, const char _user *buf, size_t count, loff_t *ppos)

{

unsigned tmp = count;

unsigned long i = 0;

memset (Mem, 0, 4);

if (Count > 4)

{

TMP = 4;

}

Copy_from_user (MEM, BUF, TMP)

for (i = 0; i < 4; i++)

{

TMP = IOREAD32 (S3c64xx_gpmdat);

if (mem[i] = = ' 1 ')

{

TMP &= (~ (1 << i));

}

Else

{

TMP |= (1 << i);

}

IOWRITE32 (TMP, S3C64XX_GPMDAT);

}

return count;

}

Controlling LEDs with I/O commands

Static long s3c6410_leds_ioctl (struct file *filp, unsigned int cmd, unsigned long arg)

{

Switch (CMD)

{

unsigned tmp;

Case 0:

Case 1:

if (Arg > 4)

Return-einval;

TMP = IOREADE32 (tmp, S3C64XX_GPMDAT);

if (cmd = = 1)

TMP &= (~ (1 << arg));

Else

TMP |= (1 << Arg);

IOWRITE32 (TMP, S3C64XX_GPMDAT);

return 0;

Default

Return-einval;

}

}

LED: Control Light Emitting diode