嵌入式Linux之我行，主要讲述和总结了本人在学习嵌入式linux中的每个步骤。一为总结经验，二希望能给想入门嵌入式Linux的朋友提供方便。如有错误之处，谢请指正。
一、开发环境
- 主 机：VMWare--Fedora 9
- 开发板：Mini2440--64MB Nand
- 编译器：arm-linux-gcc-4.3.2
二、实现步骤
1. 硬件原理图分析。由原理图得知LED电路是共阳极的，并分别由2440的GPB5、GPB6、GPB7、GPB8口控制的
2. 去掉内核已有的LED驱动设置，因为IO口与mini2440开发板的不一致，根本就不能控制板上的LED。
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#gedit arch/arm/plat-s3c24xx/common-smdk.c //注释掉以下内容 |
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/* LED devices */
/*
static struct s3c24xx_led_platdata smdk_pdata_led4 = {
.gpio = S3C2410_GPF4,
.flags = S3C24XX_LEDF_ACTLOW | S3C24XX_LEDF_TRISTATE,
.name = "led4",
.def_trigger = "timer",
};
static struct s3c24xx_led_platdata smdk_pdata_led5 = {
.gpio = S3C2410_GPF5,
.flags = S3C24XX_LEDF_ACTLOW | S3C24XX_LEDF_TRISTATE,
.name = "led5",
.def_trigger = "nand-disk",
};
static struct s3c24xx_led_platdata smdk_pdata_led6 = {
.gpio = S3C2410_GPF6,
.flags = S3C24XX_LEDF_ACTLOW | S3C24XX_LEDF_TRISTATE,
.name = "led6",
};
static struct s3c24xx_led_platdata smdk_pdata_led7 = {
.gpio = S3C2410_GPF7,
.flags = S3C24XX_LEDF_ACTLOW | S3C24XX_LEDF_TRISTATE,
.name = "led7",
};
static struct platform_device smdk_led4 = {
.name = "s3c24xx_led",
.id = 0,
.dev = {
.platform_data = &smdk_pdata_led4,
},
};
static struct platform_device smdk_led5 = {
.name = "s3c24xx_led",
.id = 1,
.dev = {
.platform_data = &smdk_pdata_led5,
},
};
static struct platform_device smdk_led6 = {
.name = "s3c24xx_led",
.id = 2,
.dev = {
.platform_data = &smdk_pdata_led6,
},
};
static struct platform_device smdk_led7 = {
.name = "s3c24xx_led",
.id = 3,
.dev = {
.platform_data = &smdk_pdata_led7,
},
};*/ |
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static struct platform_device __initdata *smdk_devs[] = {
&s3c_device_nand,
/*&smdk_led4,
&smdk_led5,
&smdk_led6,
&smdk_led7,*/
}; |
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void __init smdk_machine_init(void)
{
/* Configure the LEDs (even if we have no LED support)*/
/*
s3c2410_gpio_cfgpin(S3C2410_GPF4, S3C2410_GPF4_OUTP);
s3c2410_gpio_cfgpin(S3C2410_GPF5, S3C2410_GPF5_OUTP);
s3c2410_gpio_cfgpin(S3C2410_GPF6, S3C2410_GPF6_OUTP);
s3c2410_gpio_cfgpin(S3C2410_GPF7, S3C2410_GPF7_OUTP);
s3c2410_gpio_setpin(S3C2410_GPF4, 1);
s3c2410_gpio_setpin(S3C2410_GPF5, 1);
s3c2410_gpio_setpin(S3C2410_GPF6, 1);
s3c2410_gpio_setpin(S3C2410_GPF7, 1);*/
if (machine_is_smdk2443())
smdk_nand_info.twrph0 = 50;
s3c_device_nand.dev.platform_data = &smdk_nand_info;
platform_add_devices(smdk_devs, ARRAY_SIZE(smdk_devs));
s3c_pm_init();
} |
3. 编写适合mini2440开发板的LED驱动，代码如下，文件名称：my2440_leds.c
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/*
==============================================
Name : my2440_leds.c
Author : Huang Gang
Date : 05/11/2009
Copyright : GPL
Description : my2440 leds driver
==============================================
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <mach/hardware.h>
#include <mach/regs-gpio.h>
#define DEVICE_NAME "my2440_leds" //设备名称
#define LED_MAJOR 231 //主设备号
#define LED_ON 1 //LED亮状态
#define LED_OFF 0 //LED灭状态
static unsigned long led_table[] = //控制LED的IO口
{
S3C2410_GPB5,
S3C2410_GPB6,
S3C2410_GPB7,
S3C2410_GPB8,
};
static unsigned int led_cfg_table[] = //LED IO口的模式
{
S3C2410_GPB5_OUTP,
S3C2410_GPB6_OUTP,
S3C2410_GPB7_OUTP,
S3C2410_GPB8_OUTP,
};
static int leds_open(struct inode *inode, struct file *file)
{
return 0;
}
static int leds_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
{
//检测是第几个LED，因开发板上只有4个，索引从0开始
if(arg < 0 || arg > 3)
{
return -EINVAL;
}
//判断LED要执行哪种状态
switch(cmd)
{
case LED_ON:
{
s3c2410_gpio_setpin(led_table[arg], ~(LED_ON));
break;
}
case LED_OFF:
{
s3c2410_gpio_setpin(led_table[arg], ~(LED_OFF));
break;
}
default:
{
return -EINVAL;
}
}
return 0;
}
static struct file_operations leds_fops =
{
.owner = THIS_MODULE,
.open = leds_open,
.ioctl = leds_ioctl,
};
static int __init led_init(void)
{
int ret, i;
for(i = 0; i < 4; i++)
{
//初始化各IO口为输出模式
s3c2410_gpio_cfgpin(led_table[i], led_cfg_table[i]);
//由原理图可知LED电路是共阳极的(即各IO口输出低电平0才会点亮)
//这里初始化为1，不让LED点亮
s3c2410_gpio_setpin(led_table[i], ~(LED_OFF));
}
//注册LED设备为字符设备
ret = register_chrdev(LED_MAJOR, DEVICE_NAME, &leds_fops);
if(ret < 0)
{
printk(DEVICE_NAME " register falid!\n");
return ret;
}
}
static void __exit led_exit(void)
{
//注销设备
unregister_chrdev(LED_MAJOR, DEVICE_NAME);
}
module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Huang Gang");
MODULE_DESCRIPTION("My2440 led driver"); |
4. 把LED驱动代码部署到内核中去
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#cp -f my2440_leds.c /linux-2.6.30.4/drivers/char //把驱动源码复制到内核驱动的字符设备下 |
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#gedit /linux-2.6.30.4/drivers/char/Kconfig //添加LED设备配置 |
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config MY2440_LEDS
tristate "My2440 Leds Device"
depends on ARCH_S3C2440
default y
---help---
My2440 User Leds |
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#gedit /linux-2.6.30.4/drivers/char/Makefile //添加LED设备配置 |
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obj-$(CONFIG_MY2440_LEDS) += my2440_leds.o |
5. 配置内核，选择LED设备选项
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Device Drivers --->
Character devices --->
<*> My2440 Leds Device (NEW) |
6. 编译内核并下载到开发板上，查看已加载的设备：#cat /proc/devices，可以看到my2440_leds的主设备号为231
7. 编写应用程序测试LED驱动，文件名：leds_test.c
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/*
==============================================
Name : leds_test.c
Author : Huang Gang
Date : 06/11/2009
Copyright : GPL
Description : my2440 leds driver test
==============================================
*/
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/ioctl.h>
int main(int argc, char **argv)
{
int turn, index, fd;
//检测输入的参数合法性
if(argc != 3 || sscanf(argv[2], "%d", &index) != 1 || index < 1 || index > 4)
{
printf("Usage: leds_test on|off 1|2|3|4\n");
exit(1);
}
if(strcmp(argv[1], "on") == 0)
{
turn = 1;
}
else if(strcmp(argv[1], "off") == 0)
{
turn = 0;
}
else
{
printf("Usage: leds_test on|off 1|2|3|4\n");
exit(1);
}
//打开LED设备
fd = open("/dev/my2440_leds", 0);
if(fd < 0)
{
printf("Open Led Device Faild!\n");
exit(1);
}
//IO控制
ioctl(fd, turn, index - 1);
//关闭LED设备
close(fd);
return 0;
} |
8. 在开发主机上交叉编译测试应用程序，并复制到文件系统的/usr/sbin目录下，然后重新编译文件系统下载到开发板上
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#arm-linux-gcc -o leds_test leds_test.c |
9. 在开发板上的文件系统中创建一个LED设备的节点，然后运行测试程序，效果图如下，观测开发板上的LED灯，可以看到每一步的操作对应的LED会点亮或者熄灭
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