嵌入式Linux之我行——LED驱动在2440上的实例开发 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。 #gedit arch/arm/plat-s3c24xx/common-smdk.c //注释掉以下内容 /* 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, }, };*/   static struct platform_device __initdata *smdk_devs[] = { &s3c_device_nand, /*&smdk_led4, &smdk_led5, &smdk_led6, &smdk_led7,*/ };   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   /* ============================================== 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   #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   #gedit /linux-2.6.30.4/drivers/char/Kconfig //添加LED设备配置 config MY2440_LEDS tristate "My2440 Leds Device" depends on ARCH_S3C2440 default y ---help--- My2440 User Leds   #gedit /linux-2.6.30.4/drivers/char/Makefile //添加LED设备配置 obj-$(CONFIG_MY2440_LEDS) += my2440_leds.o   5. 配置内核，选择LED设备选项   #make menuconfig 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   /* ============================================== 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   #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