/***********************************************************************************
 *                      Linux driver 板级文件跟踪一般方法
 *  声明：
 *      1. 这是本人使用vim+ctags最常用的跟踪方法，也是唯一的方法；  :)
 *      2. 本人已经在跟踪线上标注了跟踪序号，也就是先后循序；
 *      3. 就目前而言，这种方法貌似是通用的；
 *      4. 这个例子仅仅是简单的演示，并没有全部展开，如果想要进一步跟踪，
 *          继续跟就行了。
 *      5. 源代码来自：myzr_android4_2_2_1_1_0.tar.bz2
 *
 *                                    2015-6-12 晴 深圳 南山平山村 曾剑锋
 **********************************************************************************/



cat arch/arm/mach-mx6/board-mx6q_sabresd.c

......
#define SABRESD_POWER_OFF   IMX_GPIO_NR(3, 29)          <--------------------------+
......                                                                             |
                                                                                   |
#if defined(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,              \                                | |
}                                                                                | |
                                                                                 | |
static struct gpio_keys_button new_sabresd_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-key", 1, 1), --6->----*--+ |
};                    ^-----------------------7-------------------------------*----+
                                                                              |
static struct gpio_keys_platform_data new_sabresd_button_data = {  <-------+  |
    .buttons    = new_sabresd_buttons,       >-------5----->---------------*--+
    .nbuttons   = ARRAY_SIZE(new_sabresd_buttons),                         |
};                                                                         |
                                                                           |
static struct platform_device sabresd_button_device = { <--+               |
    .name           = "gpio-keys",                         |               |
    .id             = -1,                                  |               ^
    .num_resources  = 0,                                   |               |
};                                                         |               |
                                                           |               |
static void __init imx6q_add_device_buttons(void)    <-----*-------+       |
{                                                          |       |       |
    platform_device_add_data(&sabresd_button_device,  >--3-+       |       |
                &new_sabresd_button_data,                          |       |
                sizeof(new_sabresd_button_data));   >---4----------*-------+
                                                                   |
    platform_device_register(&sabresd_button_device);              |
}                                                                  |
                                                                   |
                                                                   |
......                                                             ^
/*!                                                                |
 * Board specific initialization.                                  |
 */                                                                |
static void __init mx6_sabresd_board_init(void)   <------------<---*--------<-----+
{                                                                  |              |
    ......                                                         |              |
    imx6q_add_device_buttons(); ------>-------2------>-------------+              |
    ......                                                                        |
}                                                                                 |
                                                                                  |
......                                                                            |
/*                                                                                ^
 * initialize __mach_desc_MX6Q_SABRESD data structure.                            |
 */                                                                               |
MACHINE_START(MX6Q_SABRESD, "Freescale i.MX 6Quad/DualLite/Solo Sabre-SD Board")  |
    /* Maintainer: Freescale Semiconductor, Inc. */                               |
    .boot_params = MX6_PHYS_OFFSET + 0x100,                                       |
    .fixup = fixup_mxc_board,                                                     |
    .map_io = mx6_map_io,                                                         |
    .init_irq = mx6_init_irq,                                                     |
    .init_machine = mx6_sabresd_board_init,  ----->-------1------>------->--------+
    .timer = &mx6_sabresd_timer,
    .reserve = mx6q_sabresd_reserve,
MACHINE_END