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cbdb596ca1
The "input" trigger makes the associated GPIO an input. This is to support the Raspberry Pi PWR LED, which is driven by external hardware in normal use. N.B. pwr_led is not available on Model A or B boards. leds-gpio: Implement the brightness_get method The power LED uses some clever logic that means it is driven by a voltage measuring circuit when configured as input, otherwise it is driven by the GPIO output value. This patch wires up the brightness_get method for leds-gpio so that user-space can monitor the LED value via /sys/class/gpio/led1/brightness. Using the input trigger this returns an indication of the system power health, otherwise it is just whatever value the trigger has written most recently. See: https://github.com/raspberrypi/linux/issues/1064
55 lines
1.3 KiB
C
55 lines
1.3 KiB
C
/*
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* Set LED GPIO to Input "Trigger"
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*
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* Copyright 2015 Phil Elwell <phil@raspberrypi.org>
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*
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* Based on Nick Forbes's ledtrig-default-on.c.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/leds.h>
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#include <linux/gpio.h>
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#include "../leds.h"
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static void input_trig_activate(struct led_classdev *led_cdev)
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{
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led_cdev->flags |= SET_GPIO_INPUT;
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led_set_brightness(led_cdev, 0);
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}
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static void input_trig_deactivate(struct led_classdev *led_cdev)
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{
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led_cdev->flags |= SET_GPIO_OUTPUT;
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led_set_brightness(led_cdev, 0);
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}
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static struct led_trigger input_led_trigger = {
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.name = "input",
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.activate = input_trig_activate,
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.deactivate = input_trig_deactivate,
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};
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static int __init input_trig_init(void)
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{
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return led_trigger_register(&input_led_trigger);
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}
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static void __exit input_trig_exit(void)
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{
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led_trigger_unregister(&input_led_trigger);
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}
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module_init(input_trig_init);
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module_exit(input_trig_exit);
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MODULE_AUTHOR("Phil Elwell <phil@raspberrypi.org>");
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MODULE_DESCRIPTION("Set LED GPIO to Input \"trigger\"");
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MODULE_LICENSE("GPL");
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