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 35 static bool running = true; 36 37 struct haptic_syscall_args { 38 unsigned int hid; 39 int retval; 40 }; 41 42 static void int_exit(int sig) 43 { 44 running = false; 45 exit(0); 46 } 47 48 static 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 67 static 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 88 static 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 } 114 115 int 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 } 204