1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (c) 2022 Benjamin Tissoires
3 */
4
5#include "vmlinux.h"
6#include <bpf/bpf_helpers.h>
7#include <bpf/bpf_tracing.h>
8#include "hid_bpf_helpers.h"
9
10#define HID_UP_BUTTON		0x0009
11#define HID_GD_WHEEL		0x0038
12
13SEC("fmod_ret/hid_bpf_device_event")
14int BPF_PROG(hid_event, struct hid_bpf_ctx *hctx)
15{
16	__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 9 /* size */);
17
18	if (!data)
19		return 0; /* EPERM check */
20
21	/* Touch */
22	data[1] &= 0xfd;
23
24	/* X */
25	data[4] = 0;
26	data[5] = 0;
27
28	/* Y */
29	data[6] = 0;
30	data[7] = 0;
31
32	return 0;
33}
34
35/* 72 == 360 / 5 -> 1 report every 5 degrees */
36int resolution = 72;
37int physical = 5;
38
39struct haptic_syscall_args {
40	unsigned int hid;
41	int retval;
42};
43
44static __u8 haptic_data[8];
45
46SEC("syscall")
47int set_haptic(struct haptic_syscall_args *args)
48{
49	struct hid_bpf_ctx *ctx;
50	const size_t size = sizeof(haptic_data);
51	u16 *res;
52	int ret;
53
54	if (size > sizeof(haptic_data))
55		return -7; /* -E2BIG */
56
57	ctx = hid_bpf_allocate_context(args->hid);
58	if (!ctx)
59		return -1; /* EPERM check */
60
61	haptic_data[0] = 1;  /* report ID */
62
63	ret = hid_bpf_hw_request(ctx, haptic_data, size, HID_FEATURE_REPORT, HID_REQ_GET_REPORT);
64
65	bpf_printk("probed/remove event ret value: %d", ret);
66	bpf_printk("buf: %02x %02x %02x",
67		   haptic_data[0],
68		   haptic_data[1],
69		   haptic_data[2]);
70	bpf_printk("     %02x %02x %02x",
71		   haptic_data[3],
72		   haptic_data[4],
73		   haptic_data[5]);
74	bpf_printk("     %02x %02x",
75		   haptic_data[6],
76		   haptic_data[7]);
77
78	/* whenever resolution multiplier is not 3600, we have the fixed report descriptor */
79	res = (u16 *)&haptic_data[1];
80	if (*res != 3600) {
81//		haptic_data[1] = 72; /* resolution multiplier */
82//		haptic_data[2] = 0;  /* resolution multiplier */
83//		haptic_data[3] = 0;  /* Repeat Count */
84		haptic_data[4] = 3;  /* haptic Auto Trigger */
85//		haptic_data[5] = 5;  /* Waveform Cutoff Time */
86//		haptic_data[6] = 80; /* Retrigger Period */
87//		haptic_data[7] = 0;  /* Retrigger Period */
88	} else {
89		haptic_data[4] = 0;
90	}
91
92	ret = hid_bpf_hw_request(ctx, haptic_data, size, HID_FEATURE_REPORT, HID_REQ_SET_REPORT);
93
94	bpf_printk("set haptic ret value: %d -> %d", ret, haptic_data[4]);
95
96	args->retval = ret;
97
98	hid_bpf_release_context(ctx);
99
100	return 0;
101}
102
103/* Convert REL_DIAL into REL_WHEEL */
104SEC("fmod_ret/hid_bpf_rdesc_fixup")
105int BPF_PROG(hid_rdesc_fixup, struct hid_bpf_ctx *hctx)
106{
107	__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 4096 /* size */);
108	__u16 *res, *phys;
109
110	if (!data)
111		return 0; /* EPERM check */
112
113	/* Convert TOUCH into a button */
114	data[31] = HID_UP_BUTTON;
115	data[33] = 2;
116
117	/* Convert REL_DIAL into REL_WHEEL */
118	data[45] = HID_GD_WHEEL;
119
120	/* Change Resolution Multiplier */
121	phys = (__u16 *)&data[61];
122	*phys = physical;
123	res = (__u16 *)&data[66];
124	*res = resolution;
125
126	/* Convert X,Y from Abs to Rel */
127	data[88] = 0x06;
128	data[98] = 0x06;
129
130	return 0;
131}
132
133char _license[] SEC("license") = "GPL";
134u32 _version SEC("version") = 1;
135