GPIOLED in the FreeBSD on the Raspberry Pi

FreeBSD supports GPIOLED(4).
Here is a description how to work with it on the Raspberry Pi (for example).

GPIOLED(4) is a special driver attaches a led(4) device to a GPIO pin.
After describing physical led as a gpioled(4) we control it through a led(4) device.

Raspberry Pi has one gpioled by default. This is a led «ACT» near audio output.

This led described in the file rpi.dts:

314         leds { 
315                 compatible = "gpio-leds"; 
316  
317                 ok { 
318                         label = "ok"; 
319                         gpios = <&gpio 16 1>; 
320  
321                         /* Don't change this - it configures 
322                          * how the led driver determines if 
323                          * the led is on or off when it loads. 
324                          */ 
325                         default-state = "keep"; 
326  
327                         /* This is the real default state. */ 
328                         linux,default-trigger = "default-on"; 
329                 }; 
330         };

This led has name «ok». Default state for this led is «keep». This mean that it is «on» in normal state.
To work with this led we can use device /dev/led/ok.

To turn it off we can use this command:

# echo 1 > /dev/led/ok

And to turn it on we can use this command:

# echo 0 > /dev/led/ok

We can use symbols «*», «-«, «0», «1», «f», «f1» … «f9» and so on as described in the manual page led(4).

Let’s connect usual LED to GPIO pin 25:

To describe it as GPIOLED we need to add this four strings to the file /usr/src/sys/boot/fdt/dts/arm/rpi.dts:

led25 {
	label = "led25";
	gpios = <&gpio 25 0>;
};

After changing the rpi.dts file, we need to compile it:

# cd /usr/src/sys/tools/fdt
# setenv MACHINE arm
# ./make_dtb.sh /usr/src/sys /usr/src/sys/boot/fdt/dts/arm/rpi.dts rpi.dtb

Then we need to copy the result to the directory /boot/msdos:

# cp /boot/msdos/rpi.dtb /boot/msdos/rpidtb.old
# cp rpi.dtb /boot/msdos

The new rpi.dtb less than the old one but it works.

Let’s play with our leds: