[经验]

【BeagleBone Black试用体验】+ 第十三篇 ☞给BBB写个led驱动

杨永胜

2016-10-4 15:08:46

4149

内核版本不一样的问题解决后，就到了驱动编写步骤了，涉及硬件还是从简单的led驱动开始吧。硬件电路：
我选择了60号gpio，也就是P9_12。

源码如下：

/**
* [url=home.php?mod=space&uid=1455510]@file[/url] led.c
* [url=home.php?mod=space&uid=40524]@author[/url] yang yongsheng
* @date 2016.10.3
*/
#include
#include
#include
#include // Required for the GPIO functions
#include
#include
MODULE_LICENSE("GPL");
MODULE_AUTHOR("yang yongsheng");
MODULE_DESCRIPTION("A LED test driver for the BBB");
MODULE_VERSION("0.1");
static unsigned int gpioLED = 60; ///< hard coding the LED gpio for this example to P9_23 (GPIO49)
static unsigned int numberPresses = 0; ///< For information, store the number of button presses
static bool ledOn = 0; ///< Is the LED on or off? Used to invert its state (off by default)
static unsigned int major;
static int led_open(struct inode *inode, struct file *file)
{
printk("bbb's led gpio60 will open.n");
return 0;
}
static ssize_t led_write (struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
int val;
printk("write bbb's led.n");
copy_from_user(&val, buf, count);
if (val == 1)
{
gpio_set_value(gpioLED, true);
}
else
{
gpio_set_value(gpioLED, false);
}
return 0;
}
static ssize_t led_read (struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
return 0;
}
static struct file_operations led_fops = {
.owner = THIS_MODULE,
.open = led_open,
.write = led_write,
.read = led_read,
};
static int __init led_init(void){
int result = 0;
printk(KERN_INFO "GPIO_TEST: Initializing the GPIO_TEST LKMn");
// Is the GPIO a valid GPIO number (e.g., the BBB has 4x32 but not all available)
if (!gpio_is_valid(gpioLED)){
printk(KERN_INFO "GPIO_TEST: invalid LED GPIOn");
return -ENODEV;
}
// Going to set up the LED. It is a GPIO in output mode and will be on by default
ledOn = true;
gpio_request(gpioLED, "sysfs"); // gpioLED is hardcoded to 60, request it
gpio_direction_output(gpioLED, ledOn); // Set the gpio to be in output mode and on
gpio_set_value(gpioLED, ledOn); // Not required as set by line above (here for reference)
gpio_export(gpioLED, false); // Causes gpio49 to appear in /sys/class/gpio
major = register_chrdev(0,"bbb_led",&led_fops); //注册字符驱动
return result;
}
static void __exit led_exit(void){
gpio_set_value(gpioLED, 0); // Turn the LED off, makes it clear the device was unloaded
gpio_unexport(gpioLED); // Unexport the LED GPIO
gpio_free(gpioLED); // Free the LED GPIO
unregister_chrdev(major,"bbb_led"); //卸载字符驱动
printk(KERN_INFO "GPIO_TEST: Goodbye from the LKM!n");
}
module_init(led_init);
module_exit(led_exit);