LINUX GPIO独立按键 和 GPIO矩阵键盘

  这两种情况，内核中都有考虑，都在drivers/input/keyboard/ 下面。

GPIO 独立按键是 gpio_keys.c

GPIO 矩阵键盘是 matrix_keypad.c

具体也没有什么好分析的，主要就是采用platform 方式注册input 子系统，往应用层报键值。

在此基础上，添加相关的驱动，格式很固有化。直接上自己整理的模板吧。

GPIO 独立按键

#define SABRESD_VOLUME_UP    IMX_GPIO_NR(1, 4) //得到gpio number 号
#define SABRESD_VOLUME_DN    IMX_GPIO_NR(1, 5)

//定义宏
#ifdefined(CONFIG_KEYBOARD_GPIO) || defined(CONFIG_KEYBOARD_GPIO_MODULE)
#define GPIO_BUTTON(gpio_num, ev_code, act_low, descr, wake, debounce)    \
{                                \
    .gpio        = gpio_num,                \
    .type        = EV_KEY,                \
    .code        = ev_code,                \
    .active_low    = act_low,                \
    .desc        = "btn " descr,                \
    .wakeup        = wake,                    \
    .debounce_interval = debounce,                \
}
//上面宏定义的数组
static struct gpio_keys_button CPU_NAME_buttons[] = {
    GPIO_BUTTON(SABRESD_VOLUME_UP, KEY_VOLUMEUP, 1, "volume-up", 0, 1),
    GPIO_BUTTON(SABRESD_VOLUME_DN, KEY_VOLUMEDOWN, 1, "volume-down", 0, 1),
    GPIO_BUTTON(SABRESD_POWER_OFF, KEY_POWER, 1, "power", 1, 1),
};

static struct gpio_keys_platform_data CPU_NAME_button_data = {
    .buttons    = CPU_NAME_buttons,
    .nbuttons    = ARRAY_SIZE(CPU_NAME_buttons),
};
//platform device  与driver 中对应的
static struct platform_device CPU_NAME_button_device = {
    .name        = "gpio-keys",
    .id        = -1,
    .num_resources = 0,
    .dev        = {
        .platform_data = &CPU_NAME_button_data,
    }
};
//注册设备的函数
static void __init CPU_NAME_add_device_buttons(void)
{
    platform_device_register(&CPU_NAME_button_device);
}
#else
static void __init CPU_NAME_add_device_buttons(void) {}
#endif

    有些时候因不同CPU BSP 的GPIO 封装，在driver 中会出现一些问题。比如 gpio_request   可能会重复(imx287，
得到GPIO号的时候就已经request 了,太TMD超前了)  如下这段代码要屏蔽。

#if 0
                error = gpio_request(button->gpio, button->desc ?: "gpio_keys");
                if (error < 0) {
                        pr_err("gpio-keys: failed to request GPIO %d,"
                                " error %d\n", button->gpio, error);
                        goto fail2;
                }
#endif

GPIO 矩阵键盘

#if 1
/*
 * Tosa Keyboard
 */
 #include <linux/input/matrix_keypad.h>
//矩阵键盘按下时对应的键码表
static const uint32_t tosakbd_keymap[] = {
    KEY(0, 0, KEY_1),
    KEY(0, 1, KEY_2),
    KEY(0, 2, KEY_3),


    KEY(1, 0, KEY_4),
    KEY(1, 1, KEY_5),
    KEY(1, 2, KEY_6),


    KEY(2, 0, KEY_7),
    KEY(2, 1, KEY_8),
    KEY(2, 2, KEY_9),


    KEY(3, 0, KEY_UP),
    KEY(3, 1, KEY_0),
    KEY(3, 2, KEY_DOWN),

    KEY(4, 0, KEY_BACK),
    KEY(4, 1, KEY_ENTER),
    KEY(4, 2, KEY_ESC),


};

static struct  matrix_keymap_data   tosakbd_keymap_data = {
    .keymap        = tosakbd_keymap,
    .keymap_size    = ARRAY_SIZE(tosakbd_keymap),
};

//列选  得到GPIO 口number 号
static const int tosakbd_col_gpios[] =
            {
                // MXS_PIN_TO_GPIO( PINID_SSP0_DATA5), // 4
                MXS_PIN_TO_GPIO(PINID_LCD_D08), // 5
                MXS_PIN_TO_GPIO(PINID_LCD_D09), // 6
                MXS_PIN_TO_GPIO(PINID_LCD_D10) // 7
            };
//行选  得到GPIO 口number 号
static const int tosakbd_row_gpios[] =
            {
                MXS_PIN_TO_GPIO(PINID_LCD_D11), // 2
                MXS_PIN_TO_GPIO(PINID_LCD_D12), // 2
                MXS_PIN_TO_GPIO(PINID_LCD_D13), // 3
                MXS_PIN_TO_GPIO(PINID_LCD_D14),              // 1
                MXS_PIN_TO_GPIO(PINID_LCD_D15) // 0
            };
//driver 中的需要的data
static struct matrix_keypad_platform_data CPU_NAMEkbd_pdata = {
    .keymap_data        = &tosakbd_keymap_data,
    .row_gpios        = tosakbd_row_gpios,
    .col_gpios        = tosakbd_col_gpios,
    .num_row_gpios        = ARRAY_SIZE(tosakbd_row_gpios),
    .num_col_gpios        = ARRAY_SIZE(tosakbd_col_gpios),
    .col_scan_delay_us    = 10,
    .debounce_ms        = 10,
    .wakeup            = 1,

    .active_low =0 ,
};

static struct platform_device CPU_NAMEkbd_device = {
    .name        = "matrix-keypad",
    .id        = -1,
    .dev        = {
        .platform_data = &CPU_NAMEkbd_pdata,
    },
};

#endif

 上面的两种方式，有些时候因不同CPU BSP 的GPIO 封装，在driver 中会出现一些问题。由于不同CPU GPIO口
产生中断的触发方式不同，这里出现问题的更多。

err = request_irq(gpio_to_irq(pdata->row_gpios[i]),
                matrix_keypad_interrupt,
                IRQF_DISABLED |
                IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
                "matrix-keypad", keypad);

  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING   很多CPU无法同时支持上升延与下降延触发。只能选择其中一个，要么FALLING ，要么RISING。
 这两种方式，内核都已经封装成足够简单的方式了，用不着自己去写一个驱动，类似于填空就好了。