linux gpio按键驱动程序,Linux GPIO Key 驱动的加载

gpio-keys是基于input子系统实现的一个通用的GPIO按键驱动,基于platform来实现,位于drivers/input/keyboard/gpio_keys.c,这个文件是硬件无关的,而硬件有关的需要我们自己来注册.进入这个gpio_keys.c这个函数,第一步就是初始化.

static int __init gpio_keys_init(void)

{

return platform_driver_register(&gpio_keys_device_driver);

}

然后加载这个结构体:

static struct platform_driver gpio_keys_device_driver = {

.probe = gpio_keys_probe,

.remove = __devexit_p(gpio_keys_remove),

.driver = {

.name = "gpio-keys",

.owner = THIS_MODULE,

#ifdef CONFIG_PM

.pm = &gpio_keys_pm_ops,

#endif

}

};

进入后会执行probe函数,进行设备的probe.当然只是注册设备,没什么必要看.还比如gpio_keys_isr就是去抖动检测,这是上半部分函数.

static irqreturn_t gpio_keys_isr(int irq, void *dev_id)

{

struct gpio_button_data *bdata = dev_id;

struct gpio_keys_button *button = bdata->button;

BUG_ON(irq != gpio_to_irq(button->gpio));

if (button->debounce_interval)

mod_timer(&bdata->timer,

jiffies + msecs_to_jiffies(button->debounce_interval));

else

schedule_work(&bdata->work);

return IRQ_HANDLED;

}

然后由定时器在超时时候,触发的下半部分.

static void gpio_keys_work_func(struct work_struct *work)

{

struct gpio_button_data *bdata =

container_of(work, struct gpio_button_data, work);

gpio_keys_report_event(bdata);

}

既然gpio_keys这么简单,那么看看我们如何绑定.在此之前,先打开相应的头文件.

#ifndef _GPIO_KEYS_H

#define _GPIO_KEYS_H

struct gpio_keys_button {

/* Configuration parameters */

int code; /* input event code (KEY_*, SW_*) */

int gpio;

int active_low;

char *desc;

int type; /* input event type (EV_KEY, EV_SW) */

int wakeup; /* configure the button as a wake-up source */

int debounce_interval; /* debounce ticks interval in msecs */

bool can_disable;

};

struct gpio_keys_platform_data {

struct gpio_keys_button *buttons;

int nbuttons;

unsigned int rep:1; /* enable input subsystem auto repeat */

};

#endif

其中gpio_keys_button就是我们要引用到板级相关文件的一个重要的结构体,他的每个字段的意义,挑重点的说一说.

code字段,意思就是对应Linux的按键事件,gpio要对应gpio号,active_low是低电平有效,desc是功能描述,debounce_interval是消抖间隔.当然这个gpio_keys_button最终要关联到gpio_keys_platform_data里,其中nbuttons就是有的按键总数.在板级文件中要声明.比如做2个引脚,一个是F1,一个是F2的功能.

static struct gpio_keys_button mx28evk_buttons[] =

{

.gpio = MXS_PIN_TO_GPIO(MXS_PIN_ENCODE(2, 4)), /*K1 */

.code = KEY_F1,

.desc = "Button 1",

.active_low = 1,

{

.gpio = MXS_PIN_TO_GPIO(MXS_PIN_ENCODE(2, 6)), /*K2 */

.code = KEY_F2,

.desc = "Button 2",

.active_low = 1,

};