GPIOLED(4)

💅 GPIOLED(4) — bestie edition 💅

okay so this is the Kernel Interfaces Manual page for gpioled, and i'm literally about to make your whole kernel-dev career slay ✨ grab a boba and let's go 🧋💖

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✨ NAME ✨

gpioled — the GPIO LED generic device driver 🎀 (yes it's giving "i make lights blink on pins" and it does it flawlessly, no cap)

🌸 SYNOPSIS 🌸

so to compile this icon into the kernel, you literally just drop these lines into your kernel configuration file, periodt:

device gpio
device gpioled

that's it. that's the whole vibe check. you got this bestie 🫶

💅 DESCRIPTION 💅

bestie listen — gpioled is the glue that attaches a led(4)-compatible device to a GPIO pin 🔥 it's the matchmaker, the middleman, the main character of the wiring world ngl.

every LED in the system has a name, and that name is what's used to export a device as /dev/led/<name> 🦋 then you can control that GPIO pin by writing to this device, exactly the way led(4) describes. iykyk 💜

now, on a device.hints(5) based system — think MIPS vibes — these values are configurable for gpioled:

• hint.gpioled.%d.at — the gpiobus you're attaching to 🙈 normally it's assigned to gpiobus0.
• hint.gpioled.%d.name — the arbitrary name of the device in /dev/led/ to create for led(4). you name it, you own it 💅
• hint.gpioled.%d.pins — which pin on the GPIO interface gets mapped to this instance ✨ but bestie, please note: this mask should only ever have one bit set — any other bits (i.e., pins) will be flat-out ignored 🙈 okurrr.
• hint.gpioled.%d.invert — if you set this to 1, the pin gets set to 0 to light the LED, and 1 to clear it 🔄 (yes, the logic flips, it's that girl 🤸)
• hint.gpioled.%d.state — the initial state of the LED when the driver takes control over it 👑 if it's 1 or 0, the LED is on or off correspondingly. if it's -1, the LED stays in its original state, no touching, no drama 💀

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🎀 FDT(4) vibes (ARM girls, this one's for you) 🎀

on a FDT(4) based system, like ARM, the DTS part for a gpioled device usually looks like this, and yes it's giving art 🌈:

gpio: gpio {

        gpio-controller;
        ...

        led0 {
                compatible = "gpioled";
                gpios = <&gpio 16 2 0>;         /* GPIO pin 16. */
                name = "ok";
        };

        led1 {
                compatible = "gpioled";
                gpios = <&gpio 17 2 0>;         /* GPIO pin 17. */
                name = "user-led1";
        };
};

optionally — and this is lowkey the aesthetic upgrade — you can choose to combine all the LEDs under a single "gpio-leds" compatible node 🎀 like so:

simplebus0 {

        ...

        leds {
                compatible = "gpio-leds";

                led0 {
                        gpios = <&gpio 16 2 0>;
                        name = "ok"
                };

                led1 {
                        gpios = <&gpio 17 2 0>;
                        name = "user-led1"
                };
        };
};

both methods are equally supported 💖 and it's totally possible to have LEDs defined with any sort of mix between the two methods. mix and match, it's your world 🌍✨

the only restriction (and this is the important part, bestie, don't skip it 🙏): a GPIO pin cannot be mapped by two different (gpio)leds. no double-booking, no sharing, we don't do that here 💀 periodt.

for more details about the gpios property, please consult /usr/src/sys/dts/bindings-gpio.txt 📖 (yes, go read it, it's giving homework but make it cute).

the property name is the arbitrary name of the device in /dev/led/ to create for led(4) 🧚 that's how you name your little light babies.

🔥 SEE ALSO 🔥

• fdt(4)
• gpio(4)
• gpioiic(4)
• led(4)

go read them, they're all iconic in their own way 👑

⭐ HISTORY ⭐

the gpioled manual page first appeared in FreeBSD 10.1 🎉 a legend was born.

🌸 AUTHORS 🌸

this manual page was written by Luiz Otavio O Souza — thank you for your service king 🫶✨

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and that's the whole page bestie 💖 written with love, Debian, May 23, 2019, for GPIOLED(4) — you're gonna do amazing things with those LEDs, i can feel it 🌟💅🎀