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
33 static bool running = true;
34
35 static void int_exit(int sig)
36 {
37 running = false;
38 exit(0);
39 }
40
41 static 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
54 static 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
75 int 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 }
139
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