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Add generic connection between the kernel's LED framework and RPI's GPIO pins. Signed-off-by: Assaf Gordon <[email protected]>
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| // SPDX-License-Identifier: GPL-2.0-or-later | ||
| /* | ||
| * gpio-led - generic connection of kernel's LED framework to the RPI's GPIO. | ||
| * Copyright (C) 2021 House Gordon Software Company Ltd. <[email protected]> | ||
| * | ||
| * Based on information from: | ||
| * https://mjoldfield.com/atelier/2017/03/rpi-devicetree.html | ||
| * https://www.raspberrypi.org/documentation/configuration/device-tree.md | ||
| * https://www.kernel.org/doc/html/latest/leds/index.html | ||
| * | ||
| * compile with: | ||
| * dtc -@ -Hepapr -I dts -O dtb -o gpio-led.dtbo gpio-led-overlay.dts | ||
| * | ||
| * There will be some warnings (can be ignored): | ||
| * Warning (label_is_string): /__overrides__:label: property is not a string | ||
| * Warning (unit_address_vs_reg): /fragment@0/__overlay__/led_pins@0: | ||
| * node has a unit name, but no reg property | ||
| * Warning (unit_address_vs_reg): /fragment@1/__overlay__/leds@0: | ||
| * node has a unit name, but no reg property | ||
| * Warning (gpios_property): /__overrides__: Missing property | ||
| * '#gpio-cells' in node /fragment@1/__overlay__/leds@0/led | ||
| * or bad phandle (referred from gpio[0]) | ||
| * | ||
| * Typical electrical connection is: | ||
| * RPI-GPIO.19 -> LED -> 300ohm resister -> RPI-GND | ||
| * The GPIO pin number can be changed with the 'gpio=' parameter. | ||
| * | ||
| * Test from user-space with: | ||
| * # if nothing is shown, the overlay file isn't found in /boot/overlays | ||
| * dtoverlay -a | grep gpio-led | ||
| * | ||
| * # Load the overlay | ||
| * dtoverlay gpio-led label=moo gpio=19 | ||
| * | ||
| * # if nothing is shown, the overlay wasn't loaded successfully | ||
| * dtoverlay -l | grep gpio-led | ||
| * | ||
| * echo 1 > /sys/class/leds/moo/brightness | ||
| * echo 0 > /sys/class/leds/moo/brightness | ||
| * echo cpu > /sys/class/leds/moo/trigger | ||
| * echo heartbeat > /sys/class/leds/moo/trigger | ||
| * | ||
| * # unload the overlay | ||
| * dtoverlay -r gpio-led | ||
| * | ||
| * To load in /boot/config.txt add lines such as: | ||
| * dtoverlay=gpio-led,gpio=19,label=heart,trigger=heartbeat | ||
| * dtoverlay=gpio-led,gpio=26,label=brain,trigger=cpu | ||
| */ | ||
|
|
||
| /dts-v1/; | ||
| /plugin/; | ||
|
|
||
| / { | ||
| compatible = "brcm,bcm2835"; | ||
|
|
||
| fragment@0 { | ||
| // Configure the gpio pin controller | ||
| target = <&gpio>; | ||
| __overlay__ { | ||
| led_pin: led_pins@19 { | ||
| brcm,pins = <19>; // gpio number | ||
| brcm,function = <1>; // 0 = input, 1 = output | ||
| brcm,pull = <0>; // 0 = none, 1 = pull down, 2 = pull up | ||
| }; | ||
| }; | ||
| }; | ||
| fragment@1 { | ||
| target-path = "/"; | ||
| __overlay__ { | ||
| leds: leds@0 { | ||
| compatible = "gpio-leds"; | ||
| pinctrl-names = "default"; | ||
| pinctrl-0 = <&led_pin>; | ||
| status = "okay"; | ||
|
|
||
| led: led { | ||
| label = "myled1"; | ||
| gpios = <&gpio 19 0>; | ||
| linux,default-trigger = "none"; | ||
| }; | ||
| }; | ||
| }; | ||
| }; | ||
|
|
||
| __overrides__ { | ||
| gpio = <&led>,"gpios:4", | ||
| <&leds>,"reg:0", | ||
| <&led_pin>,"brcm,pins:0", | ||
| <&led_pin>,"reg:0"; | ||
| label = <&led>,"label"; | ||
| active_low = <&led>,"gpios:8"; | ||
| trigger = <&led>,"linux,default-trigger"; | ||
| }; | ||
|
|
||
| }; | ||
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