1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (c) 2022 Benjamin Tissoires
3 *
4 * This program will morph the Microsoft Surface Dial into a mouse,
5 * and depending on the chosen resolution enable or not the haptic feedback:
6 * - a resolution (-r) of 3600 will report 3600 "ticks" in one full rotation
7 *   without haptic feedback
8 * - any other resolution will report N "ticks" in a full rotation with haptic
9 *   feedback
10 *
11 * A good default for low resolution haptic scrolling is 72 (1 "tick" every 5
12 * degrees), and set to 3600 for smooth scrolling.
13 */
14
15#include <assert.h>
16#include <errno.h>
17#include <fcntl.h>
18#include <libgen.h>
19#include <signal.h>
20#include <stdbool.h>
21#include <stdio.h>
22#include <stdlib.h>
23#include <string.h>
24#include <sys/resource.h>
25#include <unistd.h>
26
27#include <linux/bpf.h>
28#include <linux/errno.h>
29
30#include <bpf/bpf.h>
31#include <bpf/libbpf.h>
32
33#include "hid_surface_dial.skel.h"
34#include "hid_bpf_attach.h"
35
36static bool running = true;
37
38struct haptic_syscall_args {
39	unsigned int hid;
40	int retval;
41};
42
43static void int_exit(int sig)
44{
45	running = false;
46	exit(0);
47}
48
49static void usage(const char *prog)
50{
51	fprintf(stderr,
52		"%s: %s [OPTIONS] /sys/bus/hid/devices/0BUS:0VID:0PID:00ID\n\n"
53		"  OPTIONS:\n"
54		"    -r N\t set the given resolution to the device (number of ticks per 360��)\n\n",
55		__func__, prog);
56	fprintf(stderr,
57		"This program will morph the Microsoft Surface Dial into a mouse,\n"
58		"and depending on the chosen resolution enable or not the haptic feedback:\n"
59		"- a resolution (-r) of 3600 will report 3600 'ticks' in one full rotation\n"
60		"  without haptic feedback\n"
61		"- any other resolution will report N 'ticks' in a full rotation with haptic\n"
62		"  feedback\n"
63		"\n"
64		"A good default for low resolution haptic scrolling is 72 (1 'tick' every 5\n"
65		"degrees), and set to 3600 for smooth scrolling.\n");
66}
67
68static int get_hid_id(const char *path)
69{
70	const char *str_id, *dir;
71	char uevent[1024];
72	int fd;
73
74	memset(uevent, 0, sizeof(uevent));
75	snprintf(uevent, sizeof(uevent) - 1, "%s/uevent", path);
76
77	fd = open(uevent, O_RDONLY | O_NONBLOCK);
78	if (fd < 0)
79		return -ENOENT;
80
81	close(fd);
82
83	dir = basename((char *)path);
84
85	str_id = dir + sizeof("0003:0001:0A37.");
86	return (int)strtol(str_id, NULL, 16);
87}
88
89static int attach_prog(struct hid_surface_dial *skel, struct bpf_program *prog, int hid_id)
90{
91	struct attach_prog_args args = {
92		.hid = hid_id,
93		.retval = -1,
94	};
95	int attach_fd, err;
96	DECLARE_LIBBPF_OPTS(bpf_test_run_opts, tattr,
97			    .ctx_in = &args,
98			    .ctx_size_in = sizeof(args),
99	);
100
101	attach_fd = bpf_program__fd(skel->progs.attach_prog);
102	if (attach_fd < 0) {
103		fprintf(stderr, "can't locate attach prog: %m\n");
104		return 1;
105	}
106
107	args.prog_fd = bpf_program__fd(prog);
108	err = bpf_prog_test_run_opts(attach_fd, &tattr);
109	if (err) {
110		fprintf(stderr, "can't attach prog to hid device %d: %m (err: %d)\n",
111			hid_id, err);
112		return 1;
113	}
114	return 0;
115}
116
117static int set_haptic(struct hid_surface_dial *skel, int hid_id)
118{
119	struct haptic_syscall_args args = {
120		.hid = hid_id,
121		.retval = -1,
122	};
123	int haptic_fd, err;
124	DECLARE_LIBBPF_OPTS(bpf_test_run_opts, tattr,
125			    .ctx_in = &args,
126			    .ctx_size_in = sizeof(args),
127	);
128
129	haptic_fd = bpf_program__fd(skel->progs.set_haptic);
130	if (haptic_fd < 0) {
131		fprintf(stderr, "can't locate haptic prog: %m\n");
132		return 1;
133	}
134
135	err = bpf_prog_test_run_opts(haptic_fd, &tattr);
136	if (err) {
137		fprintf(stderr, "can't set haptic configuration to hid device %d: %m (err: %d)\n",
138			hid_id, err);
139		return 1;
140	}
141	return 0;
142}
143
144int main(int argc, char **argv)
145{
146	struct hid_surface_dial *skel;
147	struct bpf_program *prog;
148	const char *optstr = "r:";
149	const char *sysfs_path;
150	int opt, hid_id, resolution = 72;
151
152	while ((opt = getopt(argc, argv, optstr)) != -1) {
153		switch (opt) {
154		case 'r':
155			{
156				char *endp = NULL;
157				long l = -1;
158
159				if (optarg) {
160					l = strtol(optarg, &endp, 10);
161					if (endp && *endp)
162						l = -1;
163				}
164
165				if (l < 0) {
166					fprintf(stderr,
167						"invalid r option %s - expecting a number\n",
168						optarg ? optarg : "");
169					exit(EXIT_FAILURE);
170				};
171
172				resolution = (int) l;
173				break;
174			}
175		default:
176			usage(basename(argv[0]));
177			return 1;
178		}
179	}
180
181	if (optind == argc) {
182		usage(basename(argv[0]));
183		return 1;
184	}
185
186	sysfs_path = argv[optind];
187	if (!sysfs_path) {
188		perror("sysfs");
189		return 1;
190	}
191
192	skel = hid_surface_dial__open_and_load();
193	if (!skel) {
194		fprintf(stderr, "%s  %s:%d", __func__, __FILE__, __LINE__);
195		return -1;
196	}
197
198	hid_id = get_hid_id(sysfs_path);
199	if (hid_id < 0) {
200		fprintf(stderr, "can not open HID device: %m\n");
201		return 1;
202	}
203
204	skel->data->resolution = resolution;
205	skel->data->physical = (int)(resolution / 72);
206
207	bpf_object__for_each_program(prog, *skel->skeleton->obj) {
208		/* ignore syscalls */
209		if (bpf_program__get_type(prog) != BPF_PROG_TYPE_TRACING)
210			continue;
211
212		attach_prog(skel, prog, hid_id);
213	}
214
215	signal(SIGINT, int_exit);
216	signal(SIGTERM, int_exit);
217
218	set_haptic(skel, hid_id);
219
220	while (running)
221		sleep(1);
222
223	hid_surface_dial__destroy(skel);
224
225	return 0;
226}
227