LED wrapper functions for Linux userspace sysfs LEDs.
#include <periphery/led.h>
/* Primary Functions */
led_t *led_new(void);
int led_open(led_t *led, const char *name);
int led_read(led_t *led, bool *value);
int led_write(led_t *led, bool value);
int led_close(led_t *led);
void led_free(led_t *led);
/* Getters */
int led_get_brightness(led_t *led, unsigned int *brightness);
int led_get_max_brightness(led_t *led, unsigned int *max_brightness);
/* Setters */
int led_set_brightness(led_t *led, unsigned int brightness);
/* Miscellaneous */
int led_name(led_t *led, char *str, size_t len);
int led_tostring(led_t *led, char *str, size_t len);
/* Error Handling */
int led_errno(led_t *led);
const char *led_errmsg(led_t *led);led_t *led_new(void);Allocate an LED handle.
Returns a valid handle on success, or NULL on failure.
int led_open(led_t *led, const char *name);Open the sysfs LED with the specified name.
led should be a valid pointer to an allocated LED handle structure.
Returns 0 on success, or a negative LED error code on failure.
int led_read(led_t *led, bool *value);Read the state of the LED into value, where true is non-zero brightness, and false is zero brightness.
led should be a valid pointer to an LED handle opened with led_open(). value should be a pointer to an allocated bool.
Returns 0 on success, or a negative LED error code on failure.
int led_write(led_t *led, bool value);Write the state of the LED to value, where true is max brightness, and false is zero brightness.
led should be a valid pointer to an LED handle opened with led_open().
Returns 0 on success, or a negative LED error code on failure.
int led_close(led_t *led);Close the LED.
led should be a valid pointer to an LED handle opened with led_open().
Returns 0 on success, or a negative LED error code on failure.
void led_free(led_t *led);Free an LED handle.
int led_get_brightness(led_t *led, unsigned int *brightness);Get the brightness of the LED.
led should be a valid pointer to an LED handle opened with led_open().
Returns 0 on success, or a negative LED error code on failure.
int led_get_max_brightness(led_t *led, unsigned int *max_brightness);Get the max brightness of the LED.
led should be a valid pointer to an LED handle opened with led_open().
Returns 0 on success, or a negative LED error code on failure.
int led_set_brightness(led_t *led, unsigned int brightness);Set the brightness of the LED.
led should be a valid pointer to an LED handle opened with led_open().
Returns 0 on success, or a negative LED error code on failure.
int led_name(led_t *led, char *str, size_t len);Return the name of the sysfs LED.
led should be a valid pointer to an LED handle opened with led_open().
Returns 0 on success, or a negative LED error code on failure.
int led_tostring(led_t *led, char *str, size_t len);Return a string representation of the LED handle.
led should be a valid pointer to an LED handle opened with led_open().
This function behaves and returns like snprintf().
int led_errno(led_t *led);Return the libc errno of the last failure that occurred.
led should be a valid pointer to an LED handle opened with led_open().
const char *led_errmsg(led_t *led);Return a human readable error message of the last failure that occurred.
led should be a valid pointer to an LED handle opened with led_open().
The periphery LED functions return 0 on success or one of the negative error codes below on failure.
The libc errno of the failure in an underlying libc library call can be obtained with the led_errno() helper function. A human readable error message can be obtained with the led_errmsg() helper function.
| Error Code | Description |
|---|---|
LED_ERROR_ARG |
Invalid arguments |
LED_ERROR_OPEN |
Opening LED |
LED_ERROR_QUERY |
Querying LED attributes |
LED_ERROR_IO |
Reading/writing LED brightness |
LED_ERROR_CLOSE |
Closing LED |
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include "led.h"
int main(void) {
led_t *led;
unsigned int max_brightness;
led = led_new();
/* Open LED led0 */
if (led_open(led, "led0") < 0) {
fprintf(stderr, "led_open(): %s\n", led_errmsg(led));
exit(1);
}
/* Turn on LED (set max brightness) */
if (led_write(led, true) < 0) {
fprintf(stderr, "led_write(): %s\n", led_errmsg(led));
exit(1);
}
/* Get max brightness */
if (led_get_max_brightness(led, &max_brightness) < 0) {
fprintf(stderr, "led_get_max_brightness(): %s\n", led_errmsg(led));
exit(1);
}
/* Set half brightness */
if (led_set_brightness(led, max_brightness / 2) < 0) {
fprintf(stderr, "led_set_brightness(): %s\n", led_errmsg(led));
exit(1);
}
led_close(led);
led_free(led);
return 0;
}