LED Driver Analysis

Hybrid Equipment LED Driver Analysis

/*******************************

*

* Miscellaneous device driver: Miscdevice

*majior=10;

*

* *****************************/

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/fs.h>

#include <linux/types.h>

#include <linux/init.h>

#include <linux/moduleparam.h>//#include memory allocation functions such as <linux/slab.h>//kcalloc,kzalloc

---------IOCTL------------

#include <linux/ioctl.h>

---------Misc_register----

#include <linux/miscdevice.h>

----------Cdev--------------

#include <linux/cdev.h>

----------Delay-------------

#include <linux/delay.h>

----------GPIO---------------

#include <mach/gpio.h>

#include <mach/regs-gpio.h>

#include <plat/gpio-cfg.h>

#define S3c_gpio_special_mark (0XFFFFFFF0)

#define S3C_GPIO_SPECIAL (x) (S3c_gpio_special_mark | (x)) Kernel definition

#define DEVICE_NAME "LEDs"

static int led_gpios[] = {

S5PV210_MP04 (4),

S5PV210_MP04 (5),

S5PV210_MP04 (6),

S5PV210_MP04 (7),

};//4 an LED

#define Led_num array_size (Led_gpios)

Static long fl210_leds_ioctl (struct file *filp, unsigned int cmd,

unsigned long Arg)

{

Switch (CMD) {

Case 0:

Case 1:

if (Arg > Led_num) {

Return-einval;

}

Gpio_set_value (Led_gpios[arg],!cmd);//Set the led to fade according to CMD

PRINTK (device_name ":%ld%d\n", ARG, CMD);

Break

Default

Return-einval;

}

return 0;

}

static struct File_operations Fl210_led_dev_fops = {

. Owner = This_module,

. Unlocked_ioctl = Fl210_leds_ioctl,

};

----------------miscdevice------------------static struct Miscdevice Fl210_led_dev = {

. minor = Misc_dynamic_minor,

. Name = Device_name,

. FoPs = &fl210_led_dev_fops,

};//--------------------------------------------

static int __init fl210_led_dev_init (void) {

int ret;

int i;

for (i = 0; i < Led_num; i++) {

ret = Gpio_request (Led_gpios[i], "led");//Application Gpio Port

if (ret) {

PRINTK ("%s:request GPIO%d for LED failed, ret =%d\n", Device_name,

Led_gpios[i], ret);

return ret;

}

S3c_gpio_cfgpin (Led_gpios[i], s3c_gpio_output);//set Gpio port as output

Gpio_set_value (Led_gpios[i], 1);//Initialize the value of the Gpio port

}

ret = Misc_register (&fl210_led_dev);//Register Miscellaneous devices

PRINTK (device_name "\tinitialized\n");

PRINTK ("Led num is:%d\n", led_num);

return ret;

}

static void __exit fl210_led_dev_exit (void) {

int i;

for (i = 0; i < Led_num; i++) {

Gpio_free (Led_gpios[i]);//release Gpio port

}

Misc_deregister (&fl210_led_dev);//Logout device

}

Module_init (Fl210_led_dev_init);

Module_exit (Fl210_led_dev_exit);

Module_license ("GPL");

Module_author ("");

S5PV210_MP04 macro defined in Linux/arch/arm/mach-s5pv210/include/mach/gpio.h

#define S5PV210_MP04 (_NR) (S5pv210_gpio_mp04_start + (_NR))

S5pv210_gpio_mp04_start = S5pv210_gpio_next (S5PV210_GPIO_MP03),

#define S5PV210_GPIO_NEXT (__gpio) \ ((__gpio# #_START) + (__gpio# #_NR) + config_s3c_gpio_space + 1)

The CONFIG_S3C_GPIO_SPAC here is the kernel configuration option, which can be found in. config and my configuration is: Config_s3c_gpio_space = 0

The code above uses several functions:

Gpio_set_value ();

S3c_gpio_cfgpin ();

Gpio_request ();

Gpio_free ();

Misc_register ();

Misc_deregister ();

The following will be analyzed individually.

The test procedure is as follows:

#include <stdio.h>//#include "sys/types.h"

#include <sys/ioctl.h>

#include <stdlib.h>

#include <unistd.h>//read,write et cetera//#include "termios.h"//#include "sys/stat.h"

#include <fcntl.h>

#define LED2_ON 0x1#define Led2_off 0x0

Main (int Argc,char *argv[])

{

int FD;

if (Fd=open ("/dev/leds", O_rdwr/*| O_ndelay | o_noctty*/)) < 0)

{

printf ("Open Device failed.\r\n");

Exit (1);

}

Else

{

printf ("Open Device successed.\r\n");

}

if (argc<3)

{

/* Code */

printf ("Usage:%s <on|off num>\n", argv[0]);

Exit (1);

}

if (!strcmp (argv[1], "on"))

{

printf ("Led1 'll on!! \ n ");

if (IOCTL (Fd,led2_on,atoi (argv[2)) <0)

{

}

}

if (!strcmp (argv[1], "off"))

{

printf ("Led1 'll off!! \ n ");

if (IOCTL (Fd,led2_off,atoi (argv[2)) <0)

{

printf ("Ioctl err!! \ n ");

}

}

Close (FD);

}

First look at S3c_gpio_cfgpin ();

int s3c_gpio_cfgpin (unsigned int pin, unsigned int config)

{

struct S3c_gpio_chip *chip = s3c_gpiolib_getchip (PIN),//get the corresponding gpio struct first pointer, which contains the various parameters of the Gpio

unsigned long flags;

int offset;

int ret;

if (!chip)

Return-einval;

offset = pin-chip->chip.base;

S3c_gpio_lock (chip, flags);

RET = S3C_GPIO_DO_SETCFG (chip, offset, config);//Set the value of the Gpio status Register as Config

S3c_gpio_unlock (chip, flags);

return ret;

}

Static inline struct s3c_gpio_chip *s3c_gpiolib_getchip (unsigned int chip)

{

Return (Chip < s3c_gpio_end)? S3c_gpios[chip]: NULL;

}

static inline int s3c_gpio_do_setcfg (struct s3c_gpio_chip *chip,

unsigned int off, unsigned int config)

{

Return (Chip->config->set_config) (chip, off, config);

}

static struct S3c_gpio_cfg gpio_cfg = {

. Set_config = S3c_gpio_setcfg_s3c64xx_4bit,

. Set_pull = S3c_gpio_setpull_updown,

. Get_pull = S3c_gpio_getpull_updown,

};

int s3c_gpio_setcfg_s3c64xx_4bit (struct s3c_gpio_chip *chip,

unsigned int off, unsigned int cfg)

{

void __iomem *reg = chip->base;

unsigned int shift = (off & 7) * 4;

U32 con;

if (Off < 8 && Chip->chip.ngpio > 8)

Reg-= 4;

if (s3c_gpio_is_cfg_special (CFG)) {

CFG &= 0xf;

CFG <<= shift;

}

con = __RAW_READL (reg);//Read Gpxcon value

Con &= ~ (0xf << shift);//zeroing

Con |= cfg;//setting config

__raw_writel (Con, reg);//write value

return 0;

}

The structure of the body s3c_gpio_chip as follows:

*/struct S3c_gpio_chip {

struct gpio_chip chip;

struct S3C_GPIO_CFG *config;

struct S3C_GPIO_PM *pm;

void __iomem *base;

int eint_offset;

spinlock_t lock;

#ifdef CONFIG_PM

U32 pm_save[7]; #endif

};

static struct S3c_gpio_chip s5pv210_gpio_4bit[] = {//description of all GPIO ports in the chip

{

. Chip = {

. Base = s5pv210_gpa0 (0),

. Ngpio = S5pv210_gpio_a0_nr,

. Label = "GPA0",

. TO_IRQ = S5p_gpiolib_gpioint_to_irq,

},

},{

。。。。

}

。。。。

}；

Next look at Gpio_set_value ();

void __gpio_set_value (unsigned gpio, int value)

{

struct Gpio_chip *chip;

Chip = Gpio_to_chip (GPIO);//Returns the Gpio_desc[pin].chip pointer warn_on (extra_checks && chip->can_sleep) corresponding to the pin;

Chip->set (Chip, gpio-chip->base, value);//Call Chip->set

}

LED Driver Analysis