[systemd-devel] GPIO Reset Button

[Koen Kooi]

Op 10 nov. 2012, om 01:17 heeft Lennart Poettering <lennart at poettering.net> het volgende geschreven:

> On Fri, 02.11.12 09:56, Pawel Pastuszak (pawelpastuszak at gmail.com) wrote:
> 
>> Hi all,
>> 
>> I was wondering if there is an way to attach an GPIO line to reboot the
>> system. I am currently working on an Embedded device that has an GPIO line
>> which needs to act as an reboot button this GPIO comes up as an
>> /sys/class/gpio/gpio103/ which i want to have it trigger when it switches
>> state to low and do an system soft reboot. Does systemd allow any
>> functionally like this?
> 
> No. We only look for input devices marked with the "power-switch"
> tag. 
> 
> The kernel can create input devices for GPIO lines
> (CONFIG_KEYBOARD_GPIO), IIRC? Maybe that's useful to achieve this?

It should be a matter of:

static struct gpio_keys_button my_awesome_gpio_keys[] = {
        {
                .code                   = KEY_POWER,
                .gpio                   = GPIO_TO_PIN(1, 16),
                .active_low             = true,
                .desc                   = "left",
                .type                   = EV_KEY,
                .wakeup                 = 1,
        },
};

static struct gpio_keys_platform_data my_awesome_gpio_key_info = {
        .buttons        = my_awesome_gpio_keys,
        .nbuttons       = ARRAY_SIZE(my_awesome_gpio_keys),
};

static struct platform_device my_awesome_keys = {
        .name   = "gpio-keys",
        .id     = -1,
        .dev    = {
                .platform_data  = &my_awesome_gpio_key_info,
        },
};

Or with devicetree:

                gpio_keys {
                        compatible = "gpio-keys";
                        pinctrl-names = "default";
                        pinctrl-0 = <&bone_lcd3_cape_keys_00A0_pins>; // add a pinctrl section about if needed, otherwise delete these 2 lines

                        #address-cells = <1>;
                        #size-cells = <0>;

                        button at 1 {
                                debounce_interval = <50>;
                                linux,code = <105>; // replace with proper KEY_POWER code
                                label = "left";
                                gpios = <&gpio2 16 0x0>;
                                gpio-key,wakeup;
                                autorepeat;
                        };
		};

That will give you a native evdev device that emits KEY_POWER when you toggle the GPIO. 

regards,

Koen