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// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2022 Benjamin Tissoires
*
* This program will morph the Microsoft Surface Dial into a mouse,
* and depending on the chosen resolution enable or not the haptic feedback:
* - a resolution (-r) of 3600 will report 3600 "ticks" in one full rotation
* without haptic feedback
* - any other resolution will report N "ticks" in a full rotation with haptic
* feedback
*
* A good default for low resolution haptic scrolling is 72 (1 "tick" every 5
* degrees), and set to 3600 for smooth scrolling.
*/
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
#include <unistd.h>
#include <linux/bpf.h>
#include <linux/errno.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include "hid_surface_dial.skel.h"
static bool running = true;
struct haptic_syscall_args {
unsigned int hid;
int retval;
};
static void int_exit(int sig)
{
running = false;
exit(0);
}
static void usage(const char *prog)
{
fprintf(stderr,
"%s: %s [OPTIONS] /sys/bus/hid/devices/0BUS:0VID:0PID:00ID\n\n"
" OPTIONS:\n"
" -r N\t set the given resolution to the device (number of ticks per 360°)\n\n",
__func__, prog);
fprintf(stderr,
"This program will morph the Microsoft Surface Dial into a mouse,\n"
"and depending on the chosen resolution enable or not the haptic feedback:\n"
"- a resolution (-r) of 3600 will report 3600 'ticks' in one full rotation\n"
" without haptic feedback\n"
"- any other resolution will report N 'ticks' in a full rotation with haptic\n"
" feedback\n"
"\n"
"A good default for low resolution haptic scrolling is 72 (1 'tick' every 5\n"
"degrees), and set to 3600 for smooth scrolling.\n");
}
static int get_hid_id(const char *path)
{
const char *str_id, *dir;
char uevent[1024];
int fd;
memset(uevent, 0, sizeof(uevent));
snprintf(uevent, sizeof(uevent) - 1, "%s/uevent", path);
fd = open(uevent, O_RDONLY | O_NONBLOCK);
if (fd < 0)
return -ENOENT;
close(fd);
dir = basename((char *)path);
str_id = dir + sizeof("0003:0001:0A37.");
return (int)strtol(str_id, NULL, 16);
}
static int set_haptic(struct hid_surface_dial *skel, int hid_id)
{
struct haptic_syscall_args args = {
.hid = hid_id,
.retval = -1,
};
int haptic_fd, err;
DECLARE_LIBBPF_OPTS(bpf_test_run_opts, tattr,
.ctx_in = &args,
.ctx_size_in = sizeof(args),
);
haptic_fd = bpf_program__fd(skel->progs.set_haptic);
if (haptic_fd < 0) {
fprintf(stderr, "can't locate haptic prog: %m\n");
return 1;
}
err = bpf_prog_test_run_opts(haptic_fd, &tattr);
if (err) {
fprintf(stderr, "can't set haptic configuration to hid device %d: %m (err: %d)\n",
hid_id, err);
return 1;
}
return 0;
}
int main(int argc, char **argv)
{
struct hid_surface_dial *skel;
const char *optstr = "r:";
struct bpf_link *link;
const char *sysfs_path;
int err, opt, hid_id, resolution = 72;
while ((opt = getopt(argc, argv, optstr)) != -1) {
switch (opt) {
case 'r':
{
char *endp = NULL;
long l = -1;
if (optarg) {
l = strtol(optarg, &endp, 10);
if (endp && *endp)
l = -1;
}
if (l < 0) {
fprintf(stderr,
"invalid r option %s - expecting a number\n",
optarg ? optarg : "");
exit(EXIT_FAILURE);
};
resolution = (int) l;
break;
}
default:
usage(basename(argv[0]));
return 1;
}
}
if (optind == argc) {
usage(basename(argv[0]));
return 1;
}
sysfs_path = argv[optind];
if (!sysfs_path) {
perror("sysfs");
return 1;
}
skel = hid_surface_dial__open();
if (!skel) {
fprintf(stderr, "%s %s:%d", __func__, __FILE__, __LINE__);
return -1;
}
hid_id = get_hid_id(sysfs_path);
if (hid_id < 0) {
fprintf(stderr, "can not open HID device: %m\n");
return 1;
}
skel->struct_ops.surface_dial->hid_id = hid_id;
err = hid_surface_dial__load(skel);
if (err < 0) {
fprintf(stderr, "can not load HID-BPF program: %m\n");
return 1;
}
skel->data->resolution = resolution;
skel->data->physical = (int)(resolution / 72);
link = bpf_map__attach_struct_ops(skel->maps.surface_dial);
if (!link) {
fprintf(stderr, "can not attach HID-BPF program: %m\n");
return 1;
}
signal(SIGINT, int_exit);
signal(SIGTERM, int_exit);
set_haptic(skel, hid_id);
while (running)
sleep(1);
hid_surface_dial__destroy(skel);
return 0;
}
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