How to gets gpio status but does not change it

Question

use chardev gpiov2

int get_gpio_status(const int gpio_offset) {

    int gfd = -1, lfd = -1, ret = 0, rc, offset = -1;
    struct gpio_v2_line_request req;
    struct gpio_v2_line_values value;
    char gpio_dev[20] = "/dev/gpiochip3";

    if (offset == -1)
        offset = gpio_offset;

    memset(&req, 0, sizeof(req));
    /* Configure input mode */
    req.config.flags = GPIO_V2_LINE_FLAG_INPUT;
    req.config.num_attrs = 0;

    /* open GPIO group device, get the fd */
    gfd = open(gpio_dev, O_WRONLY);
    if (gfd == -1) {
        ret = -errno;
        return ret;
    }

    /* line offset in requested GPIO group */
    req.offsets[0] = offset;
    /* just request one line */
    req.num_lines = 1;

    ret = ioctl(gfd, GPIO_V2_GET_LINE_IOCTL, &req);
    if (ret == -1) {
            goto __exit_gfd_close;
    } else {
        lfd = req.fd;
    }

    ret =  ioctl(lfd, GPIO_V2_LINE_GET_VALUES_IOCTL, &value);

    if (ret == -1) {
        goto __exit_gfd_close;
    }

    rc = (int)value.bits;


    // close
    if ((lfd > 2) && (close(lfd) == -1))
        perror("Failed to close lfd ");
    if ((gfd > 2) && close(gfd) == -1)
        perror("Failed to close gfd ");


__exit_gfd_close:
    if ((gfd > 2) && close(gfd) == -1)
        perror("Failed to close gfd");

__exit_lfd_close:
    if ((lfd > 2) && (close(lfd) == -1))
        perror("Failed to close lfd");
    
    return rc;
}

use libgpiod

gpiod examples: Request a line as input.

use GPIOD_LINE_DIRECTION_AS_IS There is no change in the result

gpiod_line_settings_set_direction(settings, GPIOD_LINE_DIRECTION_AS_IS);

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;
}



int read_gpio_status(const int gpio_chip, const int gpio_offset) {


    const char *chip_path = gpio_chip == 0 ? GPIO_CHIP_3 : GPIO_CHIP_5;


    struct gpiod_line_request *request;
    enum gpiod_line_value value;
    int ret;

    request = request_input_line(chip_path, gpio_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, gpio_offset);

    *//* not strictly required here, but if the app wasn't exiting... *//*
    gpiod_line_request_release(request);


    return value;
}

I used the above two methods to obtain the status of gpio, and the result obtained is after modification.

I wonder if it’s because of iotcl

from linux-5.10/include/uapi/linux/gpio.h

/*
 * v2 ioctl()s
 */
#define GPIO_V2_GET_LINEINFO_IOCTL _IOWR(0xB4, 0x05, struct gpio_v2_line_info)
#define GPIO_V2_GET_LINEINFO_WATCH_IOCTL _IOWR(0xB4, 0x06, struct gpio_v2_line_info)
#define GPIO_V2_GET_LINE_IOCTL _IOWR(0xB4, 0x07, struct gpio_v2_line_request)
#define GPIO_V2_LINE_SET_CONFIG_IOCTL _IOWR(0xB4, 0x0D, struct gpio_v2_line_config)
#define GPIO_V2_LINE_GET_VALUES_IOCTL _IOWR(0xB4, 0x0E, struct gpio_v2_line_values)
#define GPIO_V2_LINE_SET_VALUES_IOCTL _IOWR(0xB4, 0x0F, struct gpio_v2_line_values)

They are all _IOWR Could this be the problem?