1// SPDX-License-Identifier: GPL-2.0-only
  2/* Copyright (c) 2022 Benjamin Tissoires
  3 *
  4 * This is a pure HID-BPF example, and should be considered as such:
  5 * on the Etekcity Scroll 6E, the X and Y axes will be swapped and
  6 * inverted. On any other device... Not sure what this will do.
  7 *
  8 * This C main file is generic though. To adapt the code and test, users
  9 * must amend only the .bpf.c file, which this program will load any
 10 * eBPF program it finds.
 11 */
 12
 13#include <assert.h>
 14#include <errno.h>
 15#include <fcntl.h>
 16#include <libgen.h>
 17#include <signal.h>
 18#include <stdbool.h>
 19#include <stdio.h>
 20#include <stdlib.h>
 21#include <string.h>
 22#include <sys/resource.h>
 23#include <unistd.h>
 24
 25#include <linux/bpf.h>
 26#include <linux/errno.h>
 27
 28#include <bpf/bpf.h>
 29#include <bpf/libbpf.h>
 30
 31#include "hid_mouse.skel.h"
 32
 33static bool running = true;
 34
 35static void int_exit(int sig)
 36{
 37	running = false;
 38	exit(0);
 39}
 40
 41static void usage(const char *prog)
 42{
 43	fprintf(stderr,
 44		"%s: %s /sys/bus/hid/devices/0BUS:0VID:0PID:00ID\n\n",
 45		__func__, prog);
 46	fprintf(stderr,
 47		"This program will upload and attach a HID-BPF program to the given device.\n"
 48		"On the Etekcity Scroll 6E, the X and Y axis will be inverted, but on any other\n"
 49		"device, chances are high that the device will not be working anymore\n\n"
 50		"consider this as a demo and adapt the eBPF program to your needs\n"
 51		"Hit Ctrl-C to unbind the program and reset the device\n");
 52}
 53
 54static int get_hid_id(const char *path)
 55{
 56	const char *str_id, *dir;
 57	char uevent[1024];
 58	int fd;
 59
 60	memset(uevent, 0, sizeof(uevent));
 61	snprintf(uevent, sizeof(uevent) - 1, "%s/uevent", path);
 62
 63	fd = open(uevent, O_RDONLY | O_NONBLOCK);
 64	if (fd < 0)
 65		return -ENOENT;
 66
 67	close(fd);
 68
 69	dir = basename((char *)path);
 70
 71	str_id = dir + sizeof("0003:0001:0A37.");
 72	return (int)strtol(str_id, NULL, 16);
 73}
 74
 75int main(int argc, char **argv)
 76{
 77	struct hid_mouse *skel;
 78	struct bpf_link *link;
 79	int err;
 80	const char *optstr = "";
 81	const char *sysfs_path;
 82	int opt, hid_id;
 83
 84	while ((opt = getopt(argc, argv, optstr)) != -1) {
 85		switch (opt) {
 86		default:
 87			usage(basename(argv[0]));
 88			return 1;
 89		}
 90	}
 91
 92	if (optind == argc) {
 93		usage(basename(argv[0]));
 94		return 1;
 95	}
 96
 97	sysfs_path = argv[optind];
 98	if (!sysfs_path) {
 99		perror("sysfs");
100		return 1;
101	}
102
103	skel = hid_mouse__open();
104	if (!skel) {
105		fprintf(stderr, "%s  %s:%d", __func__, __FILE__, __LINE__);
106		return -1;
107	}
108
109	hid_id = get_hid_id(sysfs_path);
110
111	if (hid_id < 0) {
112		fprintf(stderr, "can not open HID device: %m\n");
113		return 1;
114	}
115	skel->struct_ops.mouse_invert->hid_id = hid_id;
116
117	err = hid_mouse__load(skel);
118	if (err < 0) {
119		fprintf(stderr, "can not load HID-BPF program: %m\n");
120		return 1;
121	}
122
123	link = bpf_map__attach_struct_ops(skel->maps.mouse_invert);
124	if (!link) {
125		fprintf(stderr, "can not attach HID-BPF program: %m\n");
126		return 1;
127	}
128
129	signal(SIGINT, int_exit);
130	signal(SIGTERM, int_exit);
131
132	while (running)
133		sleep(1);
134
135	hid_mouse__destroy(skel);
136
137	return 0;
138}