gpio-keys是基于input子系統(tǒng)實現(xiàn)的一個通用的GPIO按鍵驅(qū)動,基于platform來實現(xiàn),位于drivers/input/keyboard/gpio_keys.c,這個文件是硬件無關(guān)的,而硬件有關(guān)的需要我們自己來注冊.進(jìn)入這個gpio_keys.c這個函數(shù),第一步就是初始化.

static int __init gpio_keys_init(void)

{

return platform_driver_register(&gpio_keys_device_driver);

}

然后加載這個結(jié)構(gòu)體:

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

}

};

進(jìn)入后會執(zhí)行probe函數(shù),進(jìn)行設(shè)備的probe.當(dāng)然只是注冊設(shè)備,沒什么必要看.還比如gpio_keys_isr就是去抖動檢測,這是上半部分函數(shù).

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;

}

然后由定時器在超時時候,觸發(fā)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這么簡單,那么看看我們?nèi)绾谓壎?在此之前,先打開相應(yīng)的頭文件.

#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g(shù)pio_keys_button就是我們要引用到板級相關(guān)文件的一個重要的結(jié)構(gòu)體,他的每個字段的意義,挑重點的說一說.

code字段,意思就是對應(yīng)Linux的按鍵事件,gpio要對應(yīng)gpio號,active_low是低電平有效,desc是功能描述,debounce_interval是消抖間隔.當(dāng)然這個gpio_keys_button最終要關(guān)聯(lián)到gpio_keys_platform_data里,其中nbuttons就是有的按鍵總數(shù).在板級文件中要聲明.比如做2個引腳,一個是F1,一個是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,

},

};

然后聲明一個組合起來的platform結(jié)構(gòu).

static struct gpio_keys_platform_data mx28evk_button_data =

{

.buttons = mx28evk_buttons,

.nbuttons = ARRAY_SIZE(mx28evk_button_data),

};

最后構(gòu)建device,因為所有初始化都只識別device.

static struct platform_device mx28evk_button_device =

{

.name = "gpio-keys",

.id = -1,

.dev = {

.platform_data = &mx28evk_button_data,

}

};

最后只需要注冊設(shè)備,就可以順利使用了.

static struct platform_device *mx28evk_button_device_p[] __initdata = {

&mx28evk_button_device,

};

platform_add_devices(mx28evk_button_device_p,ARRAY_SIZE(mx28evk_button_device_p));

但是,GPIO的驅(qū)動有些BUG,下次再說.可能會導(dǎo)致加載失敗,只針對MX28平臺才錯誤吧.關(guān)鍵加載如圖:

總結(jié)

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