linux GPIO驅(qū)動(dòng)

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linux GPIO驅(qū)動(dòng)

Linux 下驅(qū)動(dòng)GPIO 其實(shí)不用自己寫(xiě),最近項(xiàng)目要用到開(kāi)發(fā)板上的GPIO,搜索了一番,發(fā)現(xiàn)linux 下實(shí)現(xiàn)GPIO 驅(qū)動(dòng)實(shí)在是太方便了,有現(xiàn)成的framework 可用,基本上要做的事情就是定義一下
Linux 下通過(guò)框架實(shí)現(xiàn)LED 大致過(guò)程如下
1、實(shí)現(xiàn)框架要求的幾個(gè)函數(shù)
int gpio_request(unsigned gpio, const char *label)
void gpio_free(unsigned gpio)
int gpio_direction_input(unsigned gpio)
int gpio_direction_output(unsigned gpio, int value)
int gpio_get_value(unsigned gpio)
void gpio_set_value(unsigned gpio, int value)
int gpio_to_irq(unsigned gpio)
int irq_to_gpio(unsigned irq)
這幾個(gè)函數(shù)是硬件相關(guān)的，具體實(shí)現(xiàn)就跟硬件管腳有關(guān)了
2、在結(jié)構(gòu) gpio_led 中定義gpio 的名字,并跟gpio 管腳關(guān)聯(lián)起來(lái),然后在初始時(shí)用函數(shù)platform_add_devices加到系統(tǒng)中
3、使用時(shí)對(duì) /sys/class/leds 下的文件接口設(shè)置相應(yīng)的值即可
舉個(gè)例子，例如有1個(gè)LED 燈，需要實(shí)現(xiàn)如下功能
亮，滅，慢閃，快閃
首先實(shí)現(xiàn)
int gpio_request(unsigned gpio, const char *label)
void gpio_free(unsigned gpio)
int gpio_direction_input(unsigned gpio)
int gpio_direction_output(unsigned gpio, int value)
int gpio_get_value(unsigned gpio)
void gpio_set_value(unsigned gpio, int value)
int gpio_to_irq(unsigned gpio)
int irq_to_gpio(unsigned irq)

然后定義
/* LEDS */
static struct gpio_led default_leds[] = {
        { .name = "myboard:led0", .gpio = 4,.default_trigger = "timer" ,},
};

static struct gpio_led_platform_data myboard_led_data = {
    .num_leds = ARRAY_SIZE(default_leds),
    .leds = default_leds,
};

static struct platform_device myboard_leds = {
    .name = "leds-gpio",
    .id = -1,
    .dev = {
        .platform_data = &myboard_led_data,
    }
};

static struct platform_device *myboard_devs[] = {
    &myboard_leds,
};

static int __init my_board_setup(void)
{
    return platform_add_devices(myboard_devs, ARRAY_SIZE(myboard_devs));
}

arch_initcall(my_board_setup);

要常亮 echo 1 > /sys/class/leds/myboard:led0/brightness
要熄滅 echo 0 > /sys/class/leds/myboard:led0/brightness
要快閃 
echo 125 > /sys/class/leds/myboard:led0/delay_on
echo 375 > /sys/class/leds/myboard:led0/delay_off
要慢閃
echo 250 > /sys/class/leds/myboard:led0/delay_on
echo 750 > /sys/class/leds/myboard:led0/delay_off