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看看第一章电路板硬件原理图，板上包含四个用户可编程的发光二极管（LED），这些LED连接在ARM处理器的可编程I/O口（GPIO）上，现在来编写这些LED的驱动：
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/miscdevice.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <asm/hardware.h>
#define DEVICE_NAME "leds" /*定义led 设备的名字*/
#define LED_MAJOR 231 /*定义led 设备的主设备号*/
static unsigned long led_table[] =
{
/*I/O 方式led 设备对应的硬件资源*/
GPIO_B10, GPIO_B8, GPIO_B5, GPIO_B6,
};
/*使用ioctl 控制led*/
static int leds_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
unsigned long arg)
{
switch (cmd)
{
case 0:
case 1:
if (arg > 4)
{
return -EINVAL;
}
write_gpio_bit(led_table[arg], !cmd);
default:
return -EINVAL;
}
}
static struct file_operations leds_fops =
{
owner: THIS_MODULE, ioctl: leds_ioctl,
};
static devfs_handle_t devfs_handle;
static int __init leds_init(void)
{
int ret;
int i;
/*在内核中注册设备*/
ret = register_chrdev(LED_MAJOR, DEVICE_NAME, &leds_fops);
if (ret < 0)
{
printk(DEVICE_NAME " can't register major number\n");
return ret;
}
devfs_handle = devfs_register(NULL, DEVICE_NAME, DEVFS_FL_DEFAULT, LED_MAJOR,
0, S_IFCHR | S_IRUSR | S_IWUSR, &leds_fops, NULL);
/*使用宏进行端口初始化，set_gpio_ctrl 和write_gpio_bit 均为宏定义*/
for (i = 0; i < 8; i++)
{
set_gpio_ctrl(led_table[i] | GPIO_PULLUP_EN | GPIO_MODE_OUT);
write_gpio_bit(led_table[i], 1);
}
printk(DEVICE_NAME " initialized\n");
return 0;
}
static void __exit leds_exit(void)
{
devfs_unregister(devfs_handle);
unregister_chrdev(LED_MAJOR, DEVICE_NAME);
}
module_init(leds_init);
module_exit(leds_exit); |
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