1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
|
From 095bad7f310809a951735d03be9d06938524a6bc Mon Sep 17 00:00:00 2001
From: Assaf Gordon <assafgordon@gmail.com>
Date: Fri, 12 Mar 2021 00:13:07 -0700
Subject: [PATCH] overlays: gpio-led: new overlay
Add generic connection between the kernel's LED framework and
RPI's GPIO pins.
Signed-off-by: Assaf Gordon <assafgordon@gmail.com>
---
arch/arm/boot/dts/overlays/Makefile | 1 +
arch/arm/boot/dts/overlays/README | 56 +++++++++++
.../boot/dts/overlays/gpio-led-overlay.dts | 97 +++++++++++++++++++
3 files changed, 154 insertions(+)
create mode 100755 arch/arm/boot/dts/overlays/gpio-led-overlay.dts
--- a/arch/arm/boot/dts/overlays/Makefile
+++ b/arch/arm/boot/dts/overlays/Makefile
@@ -54,6 +54,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
gpio-ir.dtbo \
gpio-ir-tx.dtbo \
gpio-key.dtbo \
+ gpio-led.dtbo \
gpio-no-bank0-irq.dtbo \
gpio-no-irq.dtbo \
gpio-poweroff.dtbo \
--- a/arch/arm/boot/dts/overlays/README
+++ b/arch/arm/boot/dts/overlays/README
@@ -914,6 +914,62 @@ Params: gpio GPIO pin
keycode Set the key code for the button
+
+Name: gpio-led
+Info: This is a generic overlay for activating LEDs (or any other component)
+ by a GPIO pin. Multiple LEDs can be set up using multiple calls to the
+ overlay. While there are many existing methods to activate LEDs on the
+ RPi, this method offers some advantages:
+ 1) Does not require any userspace programs.
+ 2) LEDs can be connected to the kernel's led-trigger framework,
+ and drive the LED based on triggers such as cpu load, heartbeat,
+ kernel panic, key input, timers and others.
+ 3) LED can be tied to the input state of another GPIO pin.
+ 4) The LED is setup early during the kernel boot process (useful
+ for cpu/heartbeat/panic triggers).
+
+ Typical electrical connection is:
+ RPI-GPIO.19 -> LED -> 300ohm resister -> RPI-GND
+ The GPIO pin number can be changed with the 'gpio=' parameter.
+
+ To control an LED from userspace, write a 0 or 1 value:
+ echo 1 > /sys/class/leds/myled1/brightness
+ The 'myled1' name can be changed with the 'label=' parameter.
+
+ To connect the LED to a kernel trigger from userspace:
+ echo cpu > /sys/class/leds/myled1/trigger
+ echo heartbeat > /sys/class/leds/myled1/trigger
+ echo none > /sys/class/leds/myled1/trigger
+ To connect the LED to GPIO.26 pin (physical pin 37):
+ echo gpio > /sys/class/leds/myled1/trigger
+ echo 26 > /sys/class/leds/myled1/gpio
+ Available triggers:
+ cat /sys/class/leds/myled1/trigger
+
+ More information about the Linux kernel LED/Trigger system:
+ https://www.kernel.org/doc/Documentation/leds/leds-class.rst
+ https://www.kernel.org/doc/Documentation/leds/ledtrig-oneshot.rst
+Load: dtoverlay=gpio-led,<param>=<val>
+Params: gpio GPIO pin connected to the LED (default 19)
+ label The label for this LED. It will appear under
+ /sys/class/leds/<label> . Default 'myled1'.
+ trigger Set the led-trigger to connect to this LED.
+ default 'none' (LED is user-controlled).
+ Some possible triggers:
+ cpu - CPU load (all CPUs)
+ cpu0 - CPU load of first CPU.
+ mmc - disk activity (all disks)
+ panic - turn on on kernel panic
+ heartbeat - indicate system health
+ gpio - connect to a GPIO input pin (note:
+ currently the GPIO PIN can not be set
+ using overlay parameters, must be
+ done in userspace, see examples above.
+ active_low Set to 1 to turn invert the LED control
+ (writing 0 to /sys/class/leds/XXX/brightness
+ will turn on the GPIO/LED). Default '0'.
+
+
Name: gpio-no-bank0-irq
Info: Use this overlay to disable GPIO interrupts for GPIOs in bank 0 (0-27),
which can be useful for UIO drivers.
--- /dev/null
+++ b/arch/arm/boot/dts/overlays/gpio-led-overlay.dts
@@ -0,0 +1,97 @@
+// 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. <assafgordon@gmail.com>
+ *
+ * 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";
+ };
+
+};
+
|
