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mini2440_buttons.c
- #include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/delay.h>
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#include <linux/poll.h>
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#include <linux/irq.h>
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#include <asm/irq.h>
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#include <linux/interrupt.h>
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#include <asm/uaccess.h>
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#include <mach/regs-gpio.h>
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#include <mach/hardware.h>
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#include <linux/platform_device.h>
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#include <linux/cdev.h>
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#include <linux/miscdevice.h>
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#include <linux/sched.h>
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#include <linux/gpio.h>
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#define DEVICE_NAME "buttons" //设备名称
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/*定义中断所用的结构体*/
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struct button_irq_desc
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{
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int irq; //按键对应的中断号
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int pin; //按键所对应的GPIO 端口
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int pin_setting; //按键对应的引脚描述,实际并未用到,保留
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int number; //定义键值,以传递给应用层/用户态
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char *name; //每个按键的名称
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};
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/*结构体实体定义*/
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static struct button_irq_desc button_irqs [] =
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{
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{IRQ_EINT8 , S3C2410_GPG(0) , S3C2410_GPG0_EINT8 , 0, "KEY0"},
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{IRQ_EINT11, S3C2410_GPG(3) , S3C2410_GPG3_EINT11 , 1, "KEY1"},
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{IRQ_EINT13, S3C2410_GPG(5) , S3C2410_GPG5_EINT13 , 2, "KEY2"},
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{IRQ_EINT14, S3C2410_GPG(6) , S3C2410_GPG6_EINT14 , 3, "KEY3"},
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{IRQ_EINT15, S3C2410_GPG(7) , S3C2410_GPG7_EINT15 , 4, "KEY4"},
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{IRQ_EINT19, S3C2410_GPG(11), S3C2410_GPG11_EINT19, 5, "KEY5"},
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};
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/*开发板上按键的状态变量,注意这里是’0’,对应的ASCII 码为30*/
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static volatile char key_values [] = {'0', '0', '0', '0', '0', '0'};
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/*因为本驱动是基于中断方式的,在此创建一个等待队列,以配合中断函数使用;当有按键按下并读取到键值时,将会唤醒此队列,并设置中断标志,以便能通过 read 函数判断和读取键值传递到用户态;当没有按键按下时,系统并不*/
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/*会轮询按键状态,以节省时钟资源*/
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static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
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/*中断标识变量,配合上面的队列使用,中断服务程序会把它设置为1,read 函数会把它清零*/
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static volatile int ev_press = 0;
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/*本按键驱动的中断服务程序*/
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static irqreturn_t buttons_interrupt(int irq, void *dev_id)
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{
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struct button_irq_desc *button_irqs = (struct button_irq_desc *)dev_id;
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int down;
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// udelay(0);
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/*获取被按下的按键状态*/
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down = !s3c2410_gpio_getpin(button_irqs->pin);
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/*状态改变,按键被按下,从这句可以看出,当按键没有被按下的时候,寄存器的值为1(上拉),但按键被按下的时候,寄存器对应的值为0*/
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if (down != (key_values[button_irqs->number] & 1)) { // Changed
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/*如果key1 被按下,则key_value[0]就变为’1’,对应的ASCII 码为31*/
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key_values[button_irqs->number] = '0' + down;
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ev_press = 1; /*设置中断标志为1*/
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wake_up_interruptible(&button_waitq); /*唤醒等待队列*/
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}
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return IRQ_RETVAL(IRQ_HANDLED);
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}
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/**在应用程序执行open(“/dev/buttons”,…)时会调用到此函数,在这里,它的作用主要是注册6 个按键的中断。
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*所用的中断类型是IRQ_TYPE_EDGE_BOTH,也就是双沿触发,在上升沿和下降沿均会产生中断,这样做
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**是为了更加有效地判断按键状态
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*/
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static int s3c24xx_buttons_open(struct inode *inode, struct file *file)
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{
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int i;
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int err = 0;
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for (i = 0; i < sizeof(button_irqs)/sizeof(button_irqs[0]); i++)
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{
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if (button_irqs[i].irq < 0)
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{
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continue;
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}
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/*注册中断函数*/
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err = request_irq(button_irqs[i].irq, buttons_interrupt, IRQ_TYPE_EDGE_BOTH,
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button_irqs[i].name, (void *)&button_irqs[i]);
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if (err)
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break;
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}
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if (err)
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{
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/*如果出错,释放已经注册的中断,并返回*/
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i--;
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for (; i >= 0; i--)
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{
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if (button_irqs[i].irq < 0)
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{
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continue;
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}
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disable_irq(button_irqs[i].irq);
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free_irq(button_irqs[i].irq, (void *)&button_irqs[i]);
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}
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return -EBUSY;
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}
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/*注册成功,则中断队列标记为1,表示可以通过read 读取*/
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ev_press = 1;
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/*正常返回*/
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return 0;
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}
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/*
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*此函数对应应用程序的系统调用close(fd)函数,在此,它的主要作用是当关闭设备时释放6 个按键的中断*处理函数
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*/
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static int s3c24xx_buttons_close(struct inode *inode, struct file *file)
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{
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int i;
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for (i = 0; i < sizeof(button_irqs)/sizeof(button_irqs[0]); i++)
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{
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if (button_irqs[i].irq < 0)
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{
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continue;
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}
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/*释放中断号,并注销中断处理函数*/
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free_irq(button_irqs[i].irq, (void *)&button_irqs[i]);
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}
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return 0;
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}
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/*
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*对应应用程序的read(fd,…)函数,主要用来向用户空间传递键值
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*/
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static int s3c24xx_buttons_read(struct file *filp, char __user *buff, size_t count, loff_t *offp)
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{
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unsigned long err;
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if (!ev_press)
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{
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if (filp->f_flags & O_NONBLOCK)
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/*当中断标识为0 时,并且该设备是以非阻塞方式打开时,返回*/
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return -EAGAIN;
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else
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/*当中断标识为0 时,并且该设备是以阻塞方式打开时,进入休眠状态,等待被唤醒*/
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wait_event_interruptible(button_waitq, ev_press);
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}
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/*把中断标识清零*/
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ev_press = 0;
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/*一组键值被传递到用户空间*/
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err = copy_to_user(buff, (const void *)key_values, min(sizeof(key_values), count));
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return err ? -EFAULT : min(sizeof(key_values), count);
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}
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static unsigned int s3c24xx_buttons_poll( struct file *file, struct poll_table_struct *wait)
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{
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unsigned int mask = 0;
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/*把调用poll 或者select 的进程挂入队列,以便被驱动程序唤醒*/
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poll_wait(file, &button_waitq, wait);
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if (ev_press)
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mask |= POLLIN | POLLRDNORM;
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return mask;
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}
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/*设备操作集*/
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static struct file_operations dev_fops = {
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.owner = THIS_MODULE,
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.open = s3c24xx_buttons_open,
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.release = s3c24xx_buttons_close,
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.read = s3c24xx_buttons_read,
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.poll = s3c24xx_buttons_poll,
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};
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static struct miscdevice misc = {
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.minor = MISC_DYNAMIC_MINOR,
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.name = DEVICE_NAME,
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.fops = &dev_fops,
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};
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/*设备初始化,主要是注册设备*/
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static int __init dev_init(void)
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{
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int ret;
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/*把按键设备注册为misc 设备,其设备号是自动分配的*/
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ret = misc_register(&misc);
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printk (DEVICE_NAME"\tinitialized\n");
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return ret;
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}
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/*注销设备*/
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static void __exit dev_exit(void)
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{
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misc_deregister(&misc);
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}
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module_init(dev_init); //模块初始化,仅当使用insmod/podprobe 命令加载时有用,如果设备不是通过模块方式加载,此处将不会被调用
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module_exit(dev_exit); //卸载模块,当该设备通过模块方式加载后,可以通过rmmod 命令卸载,将调用此函数
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MODULE_LICENSE("GPL");//版权信息
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MODULE_AUTHOR("FriendlyARM Inc.");
将其编译进内核。
下面是测试应用程序btn-test.c:
- #include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/ioctl.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <sys/select.h>
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#include <sys/time.h>
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#include <errno.h>
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int main(void)
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{
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int buttons_fd;
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char buttons[6] = {'0', '0', '0', '0', '0', '0'}; //定义按键值变量,对于驱动函数中的key_values 数组
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/*打开按键设备/dev/buttons*/
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buttons_fd = open("/dev/buttons", 0);
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if (buttons_fd < 0)
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{
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/*打开失败则退出*/
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perror("open device buttons");
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exit(1);
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}
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/*永读按键并打印键值和状态*/
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for (;;)
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{
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char current_buttons[6];
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int count_of_changed_key;
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int i;
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/*使用read 函数读取一组按键值(6 个)*/
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if (read(buttons_fd, current_buttons, sizeof current_buttons) != sizeof current_buttons)
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{
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perror("read buttons:");
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exit(1);
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}
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/*逐个分析读取到的按键值*/
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for (i = 0, count_of_changed_key = 0; i < sizeof buttons / sizeof buttons[0]; i++) {
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if (buttons[i] != current_buttons[i])
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{
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buttons[i] = current_buttons[i];
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/*打印按键值,并标明按键按下/抬起的状态*/
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printf("%skey %d is %s", count_of_changed_key? ", ": "", i+1, buttons[i] == '0' ? "up" :
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"down");
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count_of_changed_key++;
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}
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}
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if (count_of_changed_key)
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{
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printf("\n");
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}
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}
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/*关闭按键设备文件*/
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close(buttons_fd);
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return 0;
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}
在源代码所在的命令行输入命令:
#arm-linux-gcc –o btn-test btn-test.c
这样就生成了btn-test 可执行二进制文件,使用优盘或者网络工具( 比如ftp)把它复制到开发板中,并修改该文件的属性为可执行文件,然后运行它以测试,结果如图所示:
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