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// SPDX-License-Identifier: GPL-2.0-or-later
// SPDX-FileCopyrightText: 2023 Kent Gibson <warthog618@gmail.com>
/* Minimal example of reading a single line. */
#include <errno.h>
#include <gpiod.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* Request a line as input. */
static struct gpiod_line_request *request_input_line(const char *chip_path,
unsigned int offset,
const char *consumer)
{
struct gpiod_request_config *req_cfg = NULL;
struct gpiod_line_request *request = NULL;
struct gpiod_line_settings *settings;
struct gpiod_line_config *line_cfg;
struct gpiod_chip *chip;
int ret;
chip = gpiod_chip_open(chip_path);
if (!chip)
return NULL;
settings = gpiod_line_settings_new();
if (!settings)
goto close_chip;
gpiod_line_settings_set_direction(settings, GPIOD_LINE_DIRECTION_INPUT);
line_cfg = gpiod_line_config_new();
if (!line_cfg)
goto free_settings;
ret = gpiod_line_config_add_line_settings(line_cfg, &offset, 1,
settings);
if (ret)
goto free_line_config;
if (consumer) {
req_cfg = gpiod_request_config_new();
if (!req_cfg)
goto free_line_config;
gpiod_request_config_set_consumer(req_cfg, consumer);
}
request = gpiod_chip_request_lines(chip, req_cfg, line_cfg);
gpiod_request_config_free(req_cfg);
free_line_config:
gpiod_line_config_free(line_cfg);
free_settings:
gpiod_line_settings_free(settings);
close_chip:
gpiod_chip_close(chip);
return request;
}
static int print_value(unsigned int offset, enum gpiod_line_value value)
{
if (value == GPIOD_LINE_VALUE_ACTIVE)
printf("%d=Active\n", offset);
else if (value == GPIOD_LINE_VALUE_INACTIVE) {
printf("%d=Inactive\n", offset);
} else {
fprintf(stderr, "error reading value: %s\n",
strerror(errno));
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
int main(void)
{
/* Example configuration - customize to suit your situation. */
static const char *const chip_path = "/dev/gpiochip0";
static const unsigned int line_offset = 5;
struct gpiod_line_request *request;
enum gpiod_line_value value;
int ret;
request = request_input_line(chip_path, line_offset, "get-line-value");
if (!request) {
fprintf(stderr, "failed to request line: %s\n",
strerror(errno));
return EXIT_FAILURE;
}
value = gpiod_line_request_get_value(request, line_offset);
ret = print_value(line_offset, value);
/* not strictly required here, but if the app wasn't exiting... */
gpiod_line_request_release(request);
return ret;
}
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