// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2022 Benjamin Tissoires
 *
 * This is a pure HID-BPF example, and should be considered as such:
 * on the Etekcity Scroll 6E, the X and Y axes will be swapped and
 * inverted. On any other device... Not sure what this will do.
 *
 * This C main file is generic though. To adapt the code and test, users
 * must amend only the .bpf.c file, which this program will load any
 * eBPF program it finds.
 */

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
#include <unistd.h>

#include <linux/bpf.h>
#include <linux/errno.h>

#include <bpf/bpf.h>
#include <bpf/libbpf.h>

#include "hid_mouse.skel.h"

static bool running = true;

static void int_exit(int sig)
{
        running = false;
        exit(0);
}

static void usage(const char *prog)
{
        fprintf(stderr,
                "%s: %s /sys/bus/hid/devices/0BUS:0VID:0PID:00ID\n\n",
                __func__, prog);
        fprintf(stderr,
                "This program will upload and attach a HID-BPF program to the given device.\n"
                "On the Etekcity Scroll 6E, the X and Y axis will be inverted, but on any other\n"
                "device, chances are high that the device will not be working anymore\n\n"
                "consider this as a demo and adapt the eBPF program to your needs\n"
                "Hit Ctrl-C to unbind the program and reset the device\n");
}

static int get_hid_id(const char *path)
{
        const char *str_id, *dir;
        char uevent[1024];
        int fd;

        memset(uevent, 0, sizeof(uevent));
        snprintf(uevent, sizeof(uevent) - 1, "%s/uevent", path);

        fd = open(uevent, O_RDONLY | O_NONBLOCK);
        if (fd < 0)
                return -ENOENT;

        close(fd);

        dir = basename((char *)path);

        str_id = dir + sizeof("0003:0001:0A37.");
        return (int)strtol(str_id, NULL, 16);
}

int main(int argc, char **argv)
{
        struct hid_mouse *skel;
        struct bpf_link *link;
        int err;
        const char *optstr = "";
        const char *sysfs_path;
        int opt, hid_id;

        while ((opt = getopt(argc, argv, optstr)) != -1) {
                switch (opt) {
                default:
                        usage(basename(argv[0]));
                        return 1;
                }
        }

        if (optind == argc) {
                usage(basename(argv[0]));
                return 1;
        }

        sysfs_path = argv[optind];
        if (!sysfs_path) {
                perror("sysfs");
                return 1;
        }

        skel = hid_mouse__open();
        if (!skel) {
                fprintf(stderr, "%s  %s:%d", __func__, __FILE__, __LINE__);
                return -1;
        }

        hid_id = get_hid_id(sysfs_path);

        if (hid_id < 0) {
                fprintf(stderr, "can not open HID device: %m\n");
                return 1;
        }
        skel->struct_ops.mouse_invert->hid_id = hid_id;

        err = hid_mouse__load(skel);
        if (err < 0) {
                fprintf(stderr, "can not load HID-BPF program: %m\n");
                return 1;
        }

        link = bpf_map__attach_struct_ops(skel->maps.mouse_invert);
        if (!link) {
                fprintf(stderr, "can not attach HID-BPF program: %m\n");
                return 1;
        }

        signal(SIGINT, int_exit);
        signal(SIGTERM, int_exit);

        while (running)
                sleep(1);

        hid_mouse__destroy(skel);

        return 0;
}