linux设备驱动篇之LED驱动（1）

linux设备驱动篇之LED驱动（一）

内核版本：linux-3.0

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说起这个LED设备驱动，我有一肚子苦水，期间经历的问题层出不穷，遇到的问题有以下这些：

1、网上很多的LED驱动几乎都是2.6的内核版本，但是3.0内核和2.6的内核驱动编写有很多地方是不同的在2.6上能运行的设备驱动不一定能在3.0内核上运行。这对于刚刚踏入驱动大门人，急于想了解LED驱动是什么样的，他是怎么工作的，与应用程序又是如何协同工作的呢？对于我们可能第一个要去做的就是去找个例程先跑一跑，了解是怎么回事，增强一些自信和在战略上“藐视”设备驱动的气魄。先介绍一下我的工程结构如下说是，第一个是建立在后面第三个文件s3c_led.c这个LED设备驱动上运行的led运行程序，第二个是Make文件，

linux设备驱动篇之LED驱动（1）

我先把可以运行的这个LED驱动贴上来：

（如果你拷贝到你的vim上格式多乱了的话，教你一个快速的方法：在命令行模式下连续按下gg=G这上个字符就能帮你自动调整格式。

你在下面的程序中找到这个nt led[LED_NUM] = {5,6,7,8}; /* Four LEDs use GPB5,GPB6,GPB8,GPB10 */，因为我的led是在GPBIO5、6、7、8这个几个端口，结合你自己的情况修改，其他的不用改

/*********************************************************************************
* Copyright: (C) 2012 Guo Wenxue<guowenxue@gmail.com>
* All rights reserved.
*
* Filename: s3c_led.c
* Description: This file
*
* Version: 1.0.0(07/26/2012~)
* Author: Guo Wenxue <guowenxue@gmail.com>
* ChangeLog: 1, Release initial version on "07/26/2012 10:03:40 PM"
*
********************************************************************************/

#include <linux/module.h> /* Every Linux kernel module must include this head */
#include <linux/init.h> /* Every Linux kernel module must include this head */
#include <linux/kernel.h> /* printk() */
#include <linux/fs.h> /* struct fops */
#include <linux/errno.h> /* error codes */
#include <linux/cdev.h> /* cdev_alloc() */
#include <asm/io.h> /* ioremap() */
#include <linux/ioport.h> /* request_mem_region() */

#include <asm/ioctl.h> /* Linux kernel space head file for macro _IO() to generate ioctl command */
#ifndef __KERNEL__
#include <sys/ioctl.h> /* User space head file for macro _IO() to generate ioctl command */
#endif
//#include <linux/printk.h> /* Define log level KERN_DEBUG, no need include here */

#define DRV_AUTHOR "Guo Wenxue <guowenxue@gmail.com>"
#define DRV_DESC "S3C24XX LED driver"

#define DEV_NAME "led"
#define LED_NUM 4

/* Set the LED dev major number */
//#define LED_MAJOR 79
#ifndef LED_MAJOR
#define LED_MAJOR 0
#endif

#define DRV_MAJOR_VER 1
#define DRV_MINOR_VER 0
#define DRV_REVER_VER 0

#define DISABLE 0
#define ENABLE 1

#define GPIO_INPUT 0x00
#define GPIO_OUTPUT 0x01

#define PLATDRV_MAGIC 0x60
#define LED_OFF _IO (PLATDRV_MAGIC, 0x18)
#define LED_ON _IO (PLATDRV_MAGIC, 0x19)

#define S3C_GPB_BASE 0x56000010
#define GPBCON_OFFSET 0
#define GPBDAT_OFFSET 4
#define GPBUP_OFFSET 8
#define S3C_GPB_LEN 0x10 /* 0x56000010~0x56000020 */

int led[LED_NUM] = {5,6,7,8}; /* Four LEDs use GPB5,GPB6,GPB8,GPB10 */

static void __iomem *s3c_gpb_membase;

#define s3c_gpio_write(val, reg) __raw_writel((val), (reg)+s3c_gpb_membase)
#define s3c_gpio_read(reg) __raw_readl((reg)+s3c_gpb_membase)

int dev_count = ARRAY_SIZE(led);
int dev_major = LED_MAJOR;
int dev_minor = 0;
int debug = DISABLE;

static struct cdev *led_cdev;

static int s3c_hw_init(void)
{
int i;
volatile unsigned long gpb_con, gpb_dat, gpb_up;

if(!request_mem_region(S3C_GPB_BASE, S3C_GPB_LEN, "s3c2440 led"))
{
return -EBUSY;
}

if( !(s3c_gpb_membase=ioremap(S3C_GPB_BASE, S3C_GPB_LEN)) )
{
release_mem_region(S3C_GPB_BASE, S3C_GPB_LEN);
return -ENOMEM;
}

for(i=0; i<dev_count; i++)
{
/* Set GPBCON register, set correspond GPIO port as input or output mode */
gpb_con = s3c_gpio_read(GPBCON_OFFSET);
gpb_con &= ~(0x3<<(2*led[i])); /* Clear the currespond LED GPIO configure register */
gpb_con |= GPIO_OUTPUT<<(2*led[i]); /* Set the currespond LED GPIO as output mode */
s3c_gpio_write(gpb_con, GPBCON_OFFSET);

/* Set GPBUP register, set correspond GPIO port pull up resister as enable or disable */
gpb_up = s3c_gpio_read(GPBUP_OFFSET);
//gpb_up &= ~(0x1<<led[i]); /* Enable pull up resister */
gpb_up |= (0x1<<led[i]); /* Disable pull up resister */
s3c_gpio_write(gpb_up, GPBUP_OFFSET);

/* Set GPBDAT register, set correspond GPIO port power level as high level or low level */
gpb_dat = s3c_gpio_read(GPBDAT_OFFSET);
//gpb_dat &= ~(0x1<<led[i]); /* This port set to low level, then turn LED on */
gpb_dat |= (0x1<<led[i]); /* This port set to high level, then turn LED off */
s3c_gpio_write(gpb_dat, GPBDAT_OFFSET);
}

return 0;
}

static void turn_led(int which, unsigned int cmd)
{
volatile unsigned long gpb_dat;

gpb_dat = s3c_gpio_read(GPBDAT_OFFSET);

if(LED_ON == cmd)
{
gpb_dat &= ~(0x1<<led[which]); /* Turn LED On */
}
else if(LED_OFF == cmd)
{
gpb_dat |= (0x1<<led[which]); /* Turn LED off */
}

s3c_gpio_write(gpb_dat, GPBDAT_OFFSET);
}

static void s3c_hw_term(void)
{
int i;
volatile unsigned long gpb_dat;

for(i=0; i<dev_count; i++)
{
gpb_dat = s3c_gpio_read(GPBDAT_OFFSET);
gpb_dat |= (0x1<<led[i]); /* Turn LED off */
s3c_gpio_write(gpb_dat, GPBDAT_OFFSET);
}

release_mem_region(S3C_GPB_BASE, S3C_GPB_LEN);
iounmap(s3c_gpb_membase);
}

static int led_open(struct inode *inode, struct file *file)
{
int minor = iminor(inode);

file->private_data = (void *)minor;

printk(KERN_DEBUG "/dev/led%d opened.\n", minor);
return 0;
}

static int led_release(struct inode *inode, struct file *file)
{
printk(KERN_DEBUG "/dev/led%d closed.\n", iminor(inode));

return 0;
}

static void print_help(void)
{
printk("Follow is the ioctl() commands for %s driver:\n", DEV_NAME);
//printk("Enable Driver debug command: %u\n", SET_DRV_DEBUG);
printk("Turn LED on command : %u\n", LED_ON);
printk("Turn LED off command : %u\n", LED_OFF);

return;
}

static long led_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
int which = (int)file->private_data;

switch (cmd)
{
case LED_ON:

turn_led(which, LED_ON);
break;

case LED_OFF:
turn_led(which, LED_OFF);
break;

default:
printk(KERN_ERR "%s driver don't support ioctl command=%d\n", DEV_NAME, cmd);
print_help();
break;
}

return 0;
}

static struct file_operations led_fops =
{
.owner = THIS_MODULE,
.open = led_open,
.release = led_release,
.unlocked_ioctl = led_ioctl,
};

static int __init s3c_led_init(void)
{
int result;
dev_t devno;

if( 0 != s3c_hw_init() )
{
printk(KERN_ERR "s3c2440 LED hardware initialize failure.\n");
return -ENODEV;
}

/* Alloc the device for driver */
if (0 != dev_major) /* Static */
{
devno = MKDEV(dev_major, 0);
result = register_chrdev_region (devno, dev_count, DEV_NAME);
}
else
{
result = alloc_chrdev_region(&devno, dev_minor, dev_count, DEV_NAME);
dev_major = MAJOR(devno);
}

/* Alloc for device major failure */
if (result < 0)
{
printk(KERN_ERR "S3C %s driver can't use major %d\n", DEV_NAME, dev_major);
return -ENODEV;
}
printk(KERN_DEBUG "S3C %s driver use major %d\n", DEV_NAME, dev_major);

if(NULL == (led_cdev=cdev_alloc()) )
{
printk(KERN_ERR "S3C %s driver can't alloc for the cdev.\n", DEV_NAME);
unregister_chrdev_region(devno, dev_count);
return -ENOMEM;
}
s3c_led.c

led_cdev->owner = THIS_MODULE;
cdev_init(led_cdev, &led_fops);

result = cdev_add(led_cdev, devno, dev_count);
if (0 != result)
{
printk(KERN_INFO "S3C %s driver can't reigster cdev: result=%d\n", DEV_NAME, result);
goto ERROR;
}

printk(KERN_ERR "S3C %s driver[major=%d] version %d.%d.%d installed successfully!\n",
DEV_NAME, dev_major, DRV_MAJOR_VER, DRV_MINOR_VER,DRV_REVER_VER);
return 0;

ERROR:
printk(KERN_ERR "S3C %s driver installed failure.\n", DEV_NAME);
cdev_del(led_cdev);
unregister_chrdev_region(devno, dev_count);
return result;
}

static void __exit s3c_led_exit(void)
{
dev_t devno = MKDEV(dev_major, dev_minor);

s3c_hw_term();

cdev_del(led_cdev);
unregister_chrdev_region(devno, dev_count);

printk(KERN_ERR "S3C %s driver version %d.%d.%d removed!\n",
DEV_NAME, DRV_MAJOR_VER, DRV_MINOR_VER,DRV_REVER_VER);

return ;
}

/* These two functions defined in <linux/init.h> */
module_init(s3c_led_init);
module_exit(s3c_led_exit);

module_param(debug, int, S_IRUGO);
module_param(dev_major, int, S_IRUGO);

MODULE_AUTHOR(DRV_AUTHOR);
MODULE_DESCRIPTION(DRV_DESC);
MODULE_LICENSE("GPL");

2、makefile文件的它要和你的内核一起才能工作，这里是linux-3.0，你进入linux-3.0目录后要先make一下才能在led目录下make,makefile文件代码如下所示，你有没有看到绿色的一行，你把它指定到你的内核目录就行，我的目录是home/fulinux/kernel/linux-3.0-fulinux/，所以是这样设置的

obj-m := s3c_led.o
KERNELDIR := ~/kernel/linux-3.0-fulinux/
PWD := $(shell pwd)
modules:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
modules_install:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install
clean:
rm -rf *.o *~core .depend .*.cmd *.ko *.mod.c .tmp_versions *odule* $(TARGET)

3、应用程序代码如下，编译的时候是没有用makefile文件的，你只需要用arm-linux-gcc -o led_test led_test.c命令或者你的编译器的绝对路径，我的是

/opt/buildroot-2012.08/arm920t/usr/bin/arm-linux-gcc -o led_test led_test.c

/*********************************************************************************
* Copyright: (C) 2013 fulinux<fulinux>
* All rights reserved.
*
* Filename: led_test.c
* Description: This file is used to test led
*
* Version: 1.0.0(2013年04月04日~)
* Author: fulinux <fulinux@sina.com>
* ChangeLog: 1, Release initial version on "2013年04月04日 14时19分53秒"
*
********************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>

#include <asm/ioctl.h> /* Linux kernel space head file for macro _IO() to generate ioctl command */
#ifndef __KERNEL__
#include <sys/ioctl.h> /* User space head file for macro _IO() to generate ioctl command */
#endif

#define PLATDRV_MAGIC 0x60
#define LED_OFF _IO (PLATDRV_MAGIC, 0x18)
#define LED_ON _IO (PLATDRV_MAGIC, 0x19)

int main(int argc, char **argv)
{
int on;
int led_no;
int fd;

fd = open("/dev/led", 0);
if (fd < 0) {
fd = open("/dev/led", 0);
}
if (fd < 0) {
perror("open device led");
exit(1);
}
ioctl(fd, LED_ON, 0);
close(fd);
return 0;
}