硬件信息：FL2440板子，s3c2440CPU带四个LED，分别在链接GPB5，GPB6，GPB8，GPB10
内核版本：linux-3.8.0
led驱动代码如下：
值得注意地方地方：
1，定时器的使用：在include/linux/timer.h下定义struct timer_list
struct timer_list {
/*
* All fields that change during normal runtime grouped to the
* same cacheline
*/
struct list_head entry;
unsigned long expires;
struct tvec_base *base;
void (*function)(unsigned long);
unsigned long data;
int slack;
#ifdef CONFIG_TIMER_STATS
int start_pid;
void *start_site;
char start_comm[16];
#endif
#ifdef CONFIG_LOCKDEP
struct lockdep_map lockdep_map;
#endif
};
详细参考：linux-2.4.18内核定时器的使用
2，设置lGPIO函数有中，linux-3.8.0和linux-3.0.0有所不同，具体可以参考Documentation/arm/Samsung-S3C24XX/GPIO.txt中的说明,只列出遇到变换：
| linux-3.8.0 | linux-3.0.0 | 参数是否变化 | |
| 设置GPIO高或低 | gpio_set_value（） | s3c2410_gpio_setpin() | 不变 |
| 设置GPIO工作方式 | s3c_gpio_cfgpin() | s3c2410_gpio_cfgpin() | 不变 |
3，Linux核心几个重要跟时间有关的名词或变数，HZ、tick和jiffies之间关系。
HZ：Linux核心每隔固定周期会发出timer interrupt ，HZ是用来定义每一秒有几次timer interrupts，我的机器为100 timer interrupts。
tick:就是HZ的倒数，以秒表示
jiffies：Jiffies为Linux核心变数(32位元变数，unsigned long)，它被用来纪录系统自开机以来的tick数，每发生一次timer interrupt，Jiffies变数会被加一。
4，设备节点自动创建函数：class_create()和device_create（）
从linux 内核2.6.24的某个版本之后，devfs不复存在，udev成为devfs的替代。udev处于应用层;加入对udev的支持很简单，以一个字符设备驱动led为例，在驱动初始化的代码里调用class_create为该设备创建一个class，再为每个设备调用 device_create创建对应的设备。
大致用法如下：
struct class *class = class_create(THIS_MODULE, “led”);
device_create(class, NULL, MKDEV(major_num, 0), NULL, “led”);
这样的module被加载时，udev daemon就会自动在/dev下创建my_device设备文件。
led驱动代码plat_led.c：
/********************************************************************************** Copyright: (C) 2011 Guo Wenxue<[email protected]>
* All rights reserved.
*
* Filename: s3c_led.c
* Description: This is the common LED driver runs on S3C24XX.
*
* Version: 1.0.0(10/27/2011~)
* Author: Guo Wenxue <[email protected]>
* ChangeLog: 1, Release initial version on "10/27/2011 11:39:10 AM"
*
********************************************************************************/
#include "s3c_driver.h"
#define DRV_AUTHOR "Guo Wenxue <[email protected]>"
#define DRV_DESC "S3C24XX LED driver"
/* Driver version*/
#define DRV_MAJOR_VER 1
#define DRV_MINOR_VER 0
#define DRV_REVER_VER 0
#define DEV_NAME DEV_LED_NAME
//#define DEV_MAJOR DEV_LED_MAJOR
#ifndef DEV_MAJOR
#define DEV_MAJOR 0 /* dynamic major by default */
#define TIMER_TIMEOUT 40
static int debug = DISABLE;
static int dev_major = DEV_MAJOR;
static int dev_minor = 0;
/* ============================ Platform Device part ===============================*/
/* LED hardware informtation structure*/
struct s3c_led_info
{
unsigned char num; /* The LED number */
unsigned int gpio; /* Which GPIO the LED used */
unsigned char active_level; /* The GPIO pin level(HIGHLEVEL or LOWLEVEL) to turn on or off */
unsigned char status; /* Current LED status: OFF/ON */
unsigned char blink; /* Blink or not */
};
/* The LED platform device private data structure */
struct s3c_led_platform_data
{
struct s3c_led_info *leds;
int nleds;
};
/* LED hardware informtation data*/
static struct s3c_led_info s3c_leds[] = {
[0] = {
.num = 1,
.gpio = S3C2410_GPB(5),
.active_level = LOWLEVEL,
.status = ON,
.blink = DISABLE,
},
[1] = {
.num = 2,
.gpio = S3C2410_GPB(6),
.active_level = LOWLEVEL,
.status = OFF,
.blink = DISABLE,
},
[2] = {
.num = 3,
.gpio = S3C2410_GPB(8),
.active_level = LOWLEVEL,
.status = OFF,
.blink = DISABLE,
},
[3] = {
.num = 4,
.gpio = S3C2410_GPB(10),
.active_level = LOWLEVEL,
.status = OFF,
.blink = DISABLE,
},
};
/* The LED platform device private data */
static struct s3c_led_platform_data s3c_led_data = {
.leds = s3c_leds,
.nleds = ARRAY_SIZE(s3c_leds),
};
struct led_device
{
struct s3c_led_platform_data *data;
struct cdev cdev;
struct class *dev_class;
struct timer_list blink_timer;
} led_device;
static void platform_led_release(struct device * dev)
{
int i;
struct s3c_led_platform_data *pdata = dev->platform_data;
dbg_print("%s():%d\n", __FUNCTION__,__LINE__);
/* Turn all LED off */
for(i=0; i<pdata->nleds; i++)
{
/* for linux-3.8.0 */
gpio_set_value(pdata->leds[i].gpio, ~pdata->leds[i].active_level);
#if 0
/* for linux-3.0.0 check in s3c2410_gpio_setpin() in Documentation/arm/Samsung-S3C24XX/GPIO.txt*/
s3c2410_gpio_setpin(pdata->leds[i].gpio, ~pdata->leds[i].active_level);
#endif
}
}
static struct platform_device s3c_led_device = {
.name = "s3c_led",
.id = 1,
.dev =
{
.platform_data = &s3c_led_data,
.release = platform_led_release,
},
};
/* ===================== led device driver part ===========================*/
void led_timer_handler(unsigned long data)
{
int i;
struct s3c_led_platform_data *pdata = (struct s3c_led_platform_data *)data;
for(i=0; i<pdata->nleds; i++)
{
if(ON == pdata->leds[i].status)
{
gpio_set_value(pdata->leds[i].gpio, pdata->leds[i].active_level);
}
else
{
gpio_set_value(pdata->leds[i].gpio, ~pdata->leds[i].active_level);
}
if(ENABLE == pdata->leds[i].blink ) /* LED should blink */
{
/* Switch status between 0 and 1 to turn LED ON or off */
pdata->leds[i].status = pdata->leds[i].status ^ 0x01;
}
/* time clock */
mod_timer(&(led_device.blink_timer), jiffies + TIMER_TIMEOUT);
}
}
static int led_open(struct inode *inode, struct file *file)
{
struct led_device *pdev ;
struct s3c_led_platform_data *pdata;
pdev = container_of(inode->i_cdev, struct led_device, cdev);
pdata = pdev->data;
file->private_data = pdata;
return 0;
}
static int led_release(struct inode *inode, struct file *file)
{
return 0;
}
static void print_led_help(void)
{
printk("Follow is the ioctl() command for LED driver:\n");
printk("Enable Driver debug command: %u\n", SET_DRV_DEBUG);
printk("Get Driver verion command : %u\n", GET_DRV_VER);
printk("Turn LED on command : %u\n", LED_ON);
printk("Turn LED off command : %u\n", LED_OFF);
printk("Turn LED blink command : %u\n", LED_BLINK);
}
/* compatible with kernel version >=2.6.38*/
static long led_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct s3c_led_platform_data *pdata = file->private_data;
switch (cmd)
{
case SET_DRV_DEBUG:
dbg_print("%s driver debug now.\n", DISABLE == arg ? "Disable" : "Enable");
debug = (0==arg) ? DISABLE : ENABLE;
break;
case GET_DRV_VER:
print_version(DRV_VERSION);
return DRV_VERSION;
case LED_OFF:
if(pdata->nleds <= arg)
{
printk("LED%ld doesn‘t exist\n", arg);
return -ENOTTY;
}
pdata->leds[arg].status = OFF;
pdata->leds[arg].blink = DISABLE;
break;
case LED_ON:
if(pdata->nleds <= arg)
{
printk("LED%ld doesn‘t exist\n", arg);
return -ENOTTY;
}
pdata->leds[arg].status = ON;
pdata->leds[arg].blink = DISABLE;
break;
case LED_BLINK:
if(pdata->nleds <= arg)
{
printk("LED%ld doesn‘t exist\n", arg);
return -ENOTTY;
}
pdata->leds[arg].blink = ENABLE;
pdata->leds[arg].status = ON;
break;
default:
dbg_print("%s driver don‘t support ioctl command=%d\n", DEV_NAME, cmd);
print_led_help();
return -EINVAL;
}
return 0;
}
static struct file_operations led_fops = {
.owner = THIS_MODULE,
.open = led_open,
.release = led_release,
.unlocked_ioctl = led_ioctl, /* compatible with kernel version >=2.6.38*/
};
static int s3c_led_probe(struct platform_device *dev)
{
struct s3c_led_platform_data *pdata = dev->dev.platform_data;
int result = 0;
int i;
dev_t devno;
/* Initialize the LED status */
for(i=0; i<pdata->nleds; i++)
{
s3c_gpio_cfgpin(pdata->leds[i].gpio, S3C2410_GPIO_OUTPUT);
if(ON == pdata->leds[i].status)
{
gpio_set_value(pdata->leds[i].gpio, pdata->leds[i].active_level);
}
else
{
gpio_set_value(pdata->leds[i].gpio, ~pdata->leds[i].active_level);
}
}
/* Alloc the device for driver */
if (0 != dev_major)
{
devno = MKDEV(dev_major, dev_minor);
result = register_chrdev_region(devno, 1, DEV_NAME);
}
else
{
result = alloc_chrdev_region(&devno, dev_minor, 1, DEV_NAME);
dev_major = MAJOR(devno);
}
/* Alloc for device major failure */
if (result < 0)
{
printk("%s driver can‘t get major %d\n", DEV_NAME, dev_major);
return result;
}
/* Initialize button structure and register cdev*/
memset(&led_device, 0, sizeof(led_device));
led_device.data = dev->dev.platform_data;
cdev_init (&(led_device.cdev), &led_fops);
led_device.cdev.owner = THIS_MODULE;
result = cdev_add (&(led_device.cdev), devno , 1);
if (result)
{
printk (KERN_NOTICE "error %d add %s device", result, DEV_NAME);
goto ERROR;
}
led_device.dev_class = class_create(THIS_MODULE, DEV_NAME);
if(IS_ERR(led_device.dev_class))
{
printk("%s driver create class failture\n",DEV_NAME);
result = -ENOMEM;
goto ERROR;
}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,24)
device_create(led_device.dev_class, NULL, devno, NULL, DEV_NAME);
#else
device_create(led_device.dev_class, NULL, devno, DEV_NAME);
#endif
/* Initial the LED blink timer */
init_timer(&(led_device.blink_timer));
led_device.blink_timer.function = led_timer_handler;
led_device.blink_timer.data = (unsigned long)pdata; //pass to led_timer_handler()
led_device.blink_timer.expires = jiffies + TIMER_TIMEOUT;
add_timer(&(led_device.blink_timer));
printk("S3C %s driver version %d.%d.%d initiliazed.\n", DEV_NAME, DRV_MAJOR_VER, DRV_MINOR_VER, DRV_REVER_VER);
return 0;
ERROR:
printk("S3C %s driver version %d.%d.%d install failure.\n", DEV_NAME, DRV_MAJOR_VER, DRV_MINOR_VER, DRV_REVER_VER);
cdev_del(&(led_device.cdev));
unregister_chrdev_region(devno, 1);
return result;
}
static int s3c_led_remove(struct platform_device *dev)
{
dev_t devno = MKDEV(dev_major, dev_minor);
del_timer(&(led_device.blink_timer));
cdev_del(&(led_device.cdev));
device_destroy(led_device.dev_class, devno);
class_destroy(led_device.dev_class);
unregister_chrdev_region(devno, 1);
printk("S3C %s driver removed\n", DEV_NAME);
return 0;
}
static struct platform_driver s3c_led_driver = {
.probe = s3c_led_probe,
.remove = s3c_led_remove,
.driver = {
.name = "s3c_led",
.owner = THIS_MODULE,
},
};
static int __init s3c_led_init(void)
{
int ret = 0;
ret = platform_device_register(&s3c_led_device);
if(ret)
{
printk(KERN_ERR "%s:%d: Can‘t register platform device %d\n", __FUNCTION__,__LINE__, ret);
goto fail_reg_plat_dev;
}
dbg_print("Regist S3C LED Platform Device successfully.\n");
ret = platform_driver_register(&s3c_led_driver);
if(ret)
{
printk(KERN_ERR "%s:%d: Can‘t register platform driver %d\n", __FUNCTION__,__LINE__, ret);
goto fail_reg_plat_drv;
}
dbg_print("Regist S3C LED Platform Driver successfully.\n");
return 0;
fail_reg_plat_drv:
platform_driver_unregister(&s3c_led_driver);
fail_reg_plat_dev:
return ret;
}
static void s3c_led_exit(void)
{
dbg_print("%s():%d remove LED platform drvier\n", __FUNCTION__,__LINE__);
platform_driver_unregister(&s3c_led_driver);
dbg_print("%s():%d remove LED platform device\n", __FUNCTION__,__LINE__);
platform_device_unregister(&s3c_led_device);
}
module_init(s3c_led_init);
module_exit(s3c_led_exit);
module_param(debug, int, S_IRUGO);
module_param(dev_major, int, S_IRUGO);
module_param(dev_minor, int, S_IRUGO);
MODULE_AUTHOR(DRV_AUTHOR);
MODULE_DESCRIPTION(DRV_DESC);
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:S3C24XX_led");
s3c_driver.h头文件:
/********************************************************************************
* Copyright: (C) GuoWenxue <[email protected]>
* All rights reserved.
*
* Filename: s3c_driver.h
* Description: This is the common head file for S3C24XX common driver
*
* Version: 1.0.0(10/29/2011~)
* Author: Guo Wenxue <[email protected]>
* ChangeLog: 1, Release initial version on "10/29/2011 11:27:50 AM"
*
********************************************************************************/
#ifndef __S3C_DRIVER_H
#define __S3C_DRIVER_H
#include <linux/version.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/kref.h>
#include <linux/spinlock.h>
#include <asm/uaccess.h>
#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/i2c.h>
#include <linux/string.h>
#include <linux/bcd.h>
#include <linux/miscdevice.h>
#include <linux/poll.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/sysfs.h>
#include <linux/proc_fs.h>
#include <linux/rtc.h>
#include <linux/spinlock.h>
#include <linux/usb.h>
#include <asm/uaccess.h>
#include <asm/delay.h>
#include <linux/syscalls.h> /* For sys_access*/
#include <linux/platform_device.h>
#include <linux/unistd.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial.h>
#include <linux/serial_core.h>
#include <linux/irq.h>
#include <mach/regs-gpio.h>
#include <linux/gpio.h> //linux-3.8.0的GPIO控制
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,32)
#include <mach/hardware.h>
#include <mach/gpio.h>
#include <asm/irq.h>
#else
#include <asm-arm/irq.h>
#include <asm/arch/gpio.h>
#include <asm/arch/hardware.h>
#endif
#include "plat_ioctl.h"
/* ===========================================================================
* S3C24XX device driver common macro definition
*===========================================================================*/
#define ENPULLUP 1
#define DISPULLUP 0
#define HIGHLEVEL 1
#define LOWLEVEL 0
#define INPUT 1
#define OUTPUT 0
#define OFF 0
#define ON 1
#define ENABLE 1
#define DISABLE 0
#define TRUE 1
#define FALSE 0
/* ===========================================================================
* S3C24XX device driver name and Major number define
*===========================================================================*/
#define DEV_LED_NAME "led"
#define DEV_LED_MAJOR 203
#define DEV_BUTTON_NAME "button"
#define DEV_BUTTON_MAJOR "211"
#define DEV_ADC_NAME "adc"
#define DEV_ADC_MAJOR "212"
/* ***** Bit Operate Define *****/
#define SET_BIT(data, i) ((data) |= (1 << (i))) /* Set the bit "i" in "data" to 1 */
#define CLR_BIT(data, i) ((data) &= ~(1 << (i))) /* Clear the bit "i" in "data" to 0 */
#define NOT_BIT(data, i) ((data) ^= (1 << (i))) /* Inverse the bit "i" in "data" */
#define GET_BIT(data, i) ((data) >> (i) & 1) /* Get the value of bit "i" in "data" */
#define L_SHIFT(data, i) ((data) << (i)) /* Shift "data" left for "i" bit */
#define R_SHIFT(data, i) ((data) >> (i)) /* Shift "data" Right for "i" bit */
/* ===========================================================================
* S3C24XX device driver common function definition
*===========================================================================*/
#define SLEEP(x) {DECLARE_WAIT_QUEUE_HEAD (stSleep); if (10 > x) mdelay ((x * 1000)); \
else wait_event_interruptible_timeout (stSleep, 0, (x / 10));}
#define VERSION_CODE(a,b,c) ( ((a)<<16) + ((b)<<8) + (c))
#define DRV_VERSION VERSION_CODE(DRV_MAJOR_VER, DRV_MINOR_VER, DRV_REVER_VER)
#define MAJOR_VER(a) ((a)>>16&0xFF)
#define MINOR_VER(a) ((a)>>8&0xFF)
#define REVER_VER(a) ((a)&0xFF)
#define dbg_print(format,args...) if(DISABLE!=debug) \
{printk("[kernel] ");printk(format, ##args);}
static inline void print_version(int version)
{
#ifdef __KERNEL__
printk("%d.%d.%d\n", MAJOR_VER(version), MINOR_VER(version), REVER_VER(version));
#else
printf("%d.%d.%d\n", MAJOR_VER(version), MINOR_VER(version), REVER_VER(version));
#endif
}
#endif /* __S3C_DRIVER_H */
plat_ioctl.h头文件:
/*********************************************************************************
* Copyright(c) 2011, Guo Wenxue <[email protected]>
* All ringhts reserved.
*
* Filename: s3c_ioctl.h
* Description: ioctl() cmd argument definition here
*
* ChangLog:
* 1, Version: 1.0.0
* Date: 2011-08-10
* Author: guowenxue <[email protected]>
* Descrtipion: Initial first version
*
*
********************************************************************************/
#ifndef __PLAT_IOCTL_H
#define __PLAT_IOCTL_H
#include <asm/ioctl.h>
/*===========================================================================
* Common ioctl command definition
*===========================================================================*/
#define PLATDRV_MAGIC 0x60
/*===========================================================================
* ioctl command for all the drivers 0x01~0x0F
*===========================================================================*/
/*args is enable or disable*/
#define SET_DRV_DEBUG _IO (PLATDRV_MAGIC, 0x01)
#define GET_DRV_VER _IO (PLATDRV_MAGIC, 0x02)
/*===========================================================================
* ioctl command for few ioctl() cmd driver 0x10~0x2F
*===========================================================================*/
/* LED driver */
#define LED_OFF _IO (PLATDRV_MAGIC, 0x18)
#define LED_ON _IO (PLATDRV_MAGIC, 0x19)
#define LED_BLINK _IO (PLATDRV_MAGIC, 0x1A)
#define ADC_SET_CHANNEL _IO (PLATDRV_MAGIC, 0x1B)
/*===========================================================================
* ioctl command for GPRS driver 0x30~0x4F
*===========================================================================*/
#define GPRS_POWERDOWN _IO (PLATDRV_MAGIC, 0x30)
#define GPRS_POWERON _IO (PLATDRV_MAGIC, 0x31)
#define GPRS_RESET _IO (PLATDRV_MAGIC, 0x32)
#define GPRS_POWERMON _IO (PLATDRV_MAGIC, 0x33)
#define GPRS_CHK_SIMDOOR _IO (PLATDRV_MAGIC, 0x36)
#define GPRS_SET_DTR _IO (PLATDRV_MAGIC, 0x37)
#define GPRS_SET_RTS _IO (PLATDRV_MAGIC, 0x38)
#define GPRS_GET_RING _IO (PLATDRV_MAGIC, 0x39)
#define SET_PWUP_TIME _IO (PLATDRV_MAGIC, 0x3A)
#define SET_PWDOWN_TIME _IO (PLATDRV_MAGIC, 0x3B)
#define SET_RESET_TIME _IO (PLATDRV_MAGIC, 0x3C)
#define GPRS_CHK_MODEL _IO (PLATDRV_MAGIC, 0x3E)
/*===========================================================================
* ioctl command for EEPROM driver 0x50~0x5F
*===========================================================================*/
#define LL_POWEROFF _IO (PLATDRV_MAGIC, 0x50)
#define LL_POWERON _IO (PLATDRV_MAGIC, 0x51)
#define LL_STOP _IO (PLATDRV_MAGIC, 0x52)
#define LL_START _IO (PLATDRV_MAGIC, 0x53)
#define LL_READ _IO (PLATDRV_MAGIC, 0x54)
#define LL_WRITE _IO (PLATDRV_MAGIC, 0x55)
#define LL_DATALOW _IO (PLATDRV_MAGIC, 0x56)
#define LL_ACKNAK _IO (PLATDRV_MAGIC, 0x57)
#endif /* __PLAT_IOCTL_H */
Makefil文件：
ARCH=arm920t
PROJ=fl2440
PWD=$(shell pwd)
ifneq ("${ARCH}", "x86")
CROSS_COMPILE ?= /opt/buildroot-2011.11/${ARCH}/usr/bin/arm-linux- /*指定交叉编译器*/
KERNEL_DIR = ../../kernel/linux-3.8/ /*指定内核路径*/
else
KERNEL_DIR = /lib/modules/$(shell uname -r)/build
endif
obj-m += plat_led.o
all:
make -C $(KERNEL_DIR) SUBDIRS=$(PWD) modules
@make clear
clear:
@rm -f *.o *.cmd *.mod.c
@rm -rf *~ core .depend .tmp_versions Module.symvers modules.order -f
@rm -f .*ko.* *ko.* .*.o.cmd
clean:
rm -f *.ko *.o
led测试程序：/*********************************************************************************
* Copyright: (C) 2014 zhouguangfeng<[email protected]>
* All rights reserved.
*
* Filename: test_plat_led.c
* Description: This file is used to test led platform drvier
*
* Version: 1.0.0(08/25/2014)
* Author: zhouguangfeng <[email protected]>
* ChangeLog: 1, Release initial version on "08/25/2014 04:04:26 PM"
*
********************************************************************************/
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#define PLATDRV_MAGIC 0x60
#define LED_OFF _IO (PLATDRV_MAGIC, 0x18)
#define LED_ON _IO (PLATDRV_MAGIC, 0x19)
#define LED_BLINK _IO (PLATDRV_MAGIC, 0x1A)
/********************************************************************************
* Description:
* Input Args:
* Output Args:
* Return Value:
********************************************************************************/
int main (int argc, char **argv)
{
int fd;
int i;
fd = open("/dev/led", O_RDWR, 0755);
if(fd<0)
{
printf("cannot open.\n");
goto open_err;
}
ioctl(fd, LED_BLINK, 0);
ioctl(fd, LED_OFF, 1);
ioctl(fd, LED_ON, 2);
ioctl(fd, LED_OFF, 3);
open_err:
close(fd);
return 0;
} /* ----- End of main() ----- */