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
13 SEC("struct_ops/hid_device_event")
14 int 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 */
36 int resolution = 72;
37 int physical = 5;
38
39 struct haptic_syscall_args {
40 unsigned int hid;
41 int retval;
42 };
43
44 static __u8 haptic_data[8];
45
46 SEC("syscall")
47 int 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 */
104 SEC("struct_ops/hid_rdesc_fixup")
105 int 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
133 SEC(".struct_ops.link")
134 struct hid_bpf_ops surface_dial = {
135 .hid_rdesc_fixup = (void *)hid_rdesc_fixup,
136 .hid_device_event = (void *)hid_event,
137 };
138
139 char _license[] SEC("license") = "GPL";
140 u32 _version SEC("version") = 1;
141
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