A example by gudev to list if the power_supply is from bluetooth or not.

udev-bluetooth-power_supply.c

/* -*- coding: utf-8; indent-tabs-mode: nil; tab-width: 4; c-basic-offset: 4; -*- */
/**
 * Copyright (C) 2013 Shih-Yuan Lee (FourDollars) <fourdollars@gmail.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

// gcc -Wall -Werror -g -std=c99 udev-bluetooth-power_supply.c `pkg-config --cflags --libs gudev-1.0` -o udev-bluetooth-power_supply

#include <stdio.h>
#include <gudev/gudev.h>

int main(int argc, char* argv[])
{
#if !defined(GLIB_VERSION_2_36)
    g_type_init ();
#endif
    GList *l = NULL;
    const gchar *subsystems[] = {"power_supply", NULL};
    GUdevClient *gudev_client = g_udev_client_new (subsystems);

    for (int i=0; subsystems[i] != NULL; i++) {
        GList *devices = g_udev_client_query_by_subsystem (gudev_client, subsystems[i]);

        for (l = devices; l != NULL; l = l->next) {
            GUdevDevice *native = l->data;

            printf("name: %s\n", g_udev_device_get_name (native));
            printf("sysfs: %s\n", g_udev_device_get_sysfs_path (native));
            printf("subsystem: %s\n", g_udev_device_get_subsystem (native));
            printf("devtype: %s\n", g_udev_device_get_devtype (native));
            printf("device type: %c\n", g_udev_device_get_device_type (native));
            printf("device file: %s\n", g_udev_device_get_device_file (native));
            printf("driver: %s\n", g_udev_device_get_driver (native));

            const gchar * const * symlinks = g_udev_device_get_device_file_symlinks (native);
            for (int j = 0; symlinks[j] != NULL; j++) {
                g_print("symlink: %s\n", symlinks[j]);
            }

            const gchar * const * tags = g_udev_device_get_tags (native);
            for (int j = 0; tags[j] != NULL; j++) {
                g_print("tag: %s\n", tags[j]);
            }

            GUdevDevice *parent = g_udev_device_get_parent_with_subsystem (native, "bluetooth", NULL);

            if (parent != NULL) {

                printf("\tname: %s\n", g_udev_device_get_name (parent));
                printf("\tsysfs: %s\n", g_udev_device_get_sysfs_path (parent));
                printf("\tsubsystem: %s\n", g_udev_device_get_subsystem (parent));
                printf("\tdevtype: %s\n", g_udev_device_get_devtype (parent));
                printf("\tdevice type: %c\n", g_udev_device_get_device_type (parent));
                printf("\tdevice file: %s\n", g_udev_device_get_device_file (parent));
                printf("\tdriver: %s\n", g_udev_device_get_driver (parent));

                const gchar * const * symlinks = g_udev_device_get_device_file_symlinks (parent);
                for (int j = 0; symlinks[j] != NULL; j++) {
                    g_print("\tsymlink: %s\n", symlinks[j]);
                }

                const gchar * const * tags = g_udev_device_get_tags (parent);
                for (int j = 0; tags[j] != NULL; j++) {
                    g_print("\ttag: %s\n", tags[j]);
                }

                g_object_unref (parent);
            } else {
                printf("\tNo parent\n");
            }

            printf("\n");
        }

        g_list_foreach (devices, (GFunc) g_object_unref, NULL);
        g_list_free (devices);
    }

    g_object_unref (gudev_client);

    return 0;
}

/* vim:set fileencodings=utf-8 tabstop=4 expandtab shiftwidth=4 softtabstop=4: */