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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
35static bool running = true;
36
37struct haptic_syscall_args {
38 unsigned int hid;
39 int retval;
40};
41
42static void int_exit(int sig)
43{
44 running = false;
45 exit(0);
46}
47
48static void usage(const char *prog)
49{
50 fprintf(stderr,
51 "%s: %s [OPTIONS] /sys/bus/hid/devices/0BUS:0VID:0PID:00ID\n\n"
52 " OPTIONS:\n"
53 " -r N\t set the given resolution to the device (number of ticks per 360°)\n\n",
54 __func__, prog);
55 fprintf(stderr,
56 "This program will morph the Microsoft Surface Dial into a mouse,\n"
57 "and depending on the chosen resolution enable or not the haptic feedback:\n"
58 "- a resolution (-r) of 3600 will report 3600 'ticks' in one full rotation\n"
59 " without haptic feedback\n"
60 "- any other resolution will report N 'ticks' in a full rotation with haptic\n"
61 " feedback\n"
62 "\n"
63 "A good default for low resolution haptic scrolling is 72 (1 'tick' every 5\n"
64 "degrees), and set to 3600 for smooth scrolling.\n");
65}
66
67static int get_hid_id(const char *path)
68{
69 const char *str_id, *dir;
70 char uevent[1024];
71 int fd;
72
73 memset(uevent, 0, sizeof(uevent));
74 snprintf(uevent, sizeof(uevent) - 1, "%s/uevent", path);
75
76 fd = open(uevent, O_RDONLY | O_NONBLOCK);
77 if (fd < 0)
78 return -ENOENT;
79
80 close(fd);
81
82 dir = basename((char *)path);
83
84 str_id = dir + sizeof("0003:0001:0A37.");
85 return (int)strtol(str_id, NULL, 16);
86}
87
88static int set_haptic(struct hid_surface_dial *skel, int hid_id)
89{
90 struct haptic_syscall_args args = {
91 .hid = hid_id,
92 .retval = -1,
93 };
94 int haptic_fd, err;
95 DECLARE_LIBBPF_OPTS(bpf_test_run_opts, tattr,
96 .ctx_in = &args,
97 .ctx_size_in = sizeof(args),
98 );
99
100 haptic_fd = bpf_program__fd(skel->progs.set_haptic);
101 if (haptic_fd < 0) {
102 fprintf(stderr, "can't locate haptic prog: %m\n");
103 return 1;
104 }
105
106 err = bpf_prog_test_run_opts(haptic_fd, &tattr);
107 if (err) {
108 fprintf(stderr, "can't set haptic configuration to hid device %d: %m (err: %d)\n",
109 hid_id, err);
110 return 1;
111 }
112 return 0;
113}
114
115int main(int argc, char **argv)
116{
117 struct hid_surface_dial *skel;
118 const char *optstr = "r:";
119 struct bpf_link *link;
120 const char *sysfs_path;
121 int err, opt, hid_id, resolution = 72;
122
123 while ((opt = getopt(argc, argv, optstr)) != -1) {
124 switch (opt) {
125 case 'r':
126 {
127 char *endp = NULL;
128 long l = -1;
129
130 if (optarg) {
131 l = strtol(optarg, &endp, 10);
132 if (endp && *endp)
133 l = -1;
134 }
135
136 if (l < 0) {
137 fprintf(stderr,
138 "invalid r option %s - expecting a number\n",
139 optarg ? optarg : "");
140 exit(EXIT_FAILURE);
141 };
142
143 resolution = (int) l;
144 break;
145 }
146 default:
147 usage(basename(argv[0]));
148 return 1;
149 }
150 }
151
152 if (optind == argc) {
153 usage(basename(argv[0]));
154 return 1;
155 }
156
157 sysfs_path = argv[optind];
158 if (!sysfs_path) {
159 perror("sysfs");
160 return 1;
161 }
162
163 skel = hid_surface_dial__open();
164 if (!skel) {
165 fprintf(stderr, "%s %s:%d", __func__, __FILE__, __LINE__);
166 return -1;
167 }
168
169 hid_id = get_hid_id(sysfs_path);
170 if (hid_id < 0) {
171 fprintf(stderr, "can not open HID device: %m\n");
172 return 1;
173 }
174
175 skel->struct_ops.surface_dial->hid_id = hid_id;
176
177 err = hid_surface_dial__load(skel);
178 if (err < 0) {
179 fprintf(stderr, "can not load HID-BPF program: %m\n");
180 return 1;
181 }
182
183 skel->data->resolution = resolution;
184 skel->data->physical = (int)(resolution / 72);
185
186 link = bpf_map__attach_struct_ops(skel->maps.surface_dial);
187 if (!link) {
188 fprintf(stderr, "can not attach HID-BPF program: %m\n");
189 return 1;
190 }
191
192 signal(SIGINT, int_exit);
193 signal(SIGTERM, int_exit);
194
195 set_haptic(skel, hid_id);
196
197 while (running)
198 sleep(1);
199
200 hid_surface_dial__destroy(skel);
201
202 return 0;
203}