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("struct_ops/hid_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("struct_ops/hid_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
133SEC(".struct_ops.link")
134struct hid_bpf_ops surface_dial = {
135	.hid_rdesc_fixup = (void *)hid_rdesc_fixup,
136	.hid_device_event = (void *)hid_event,
137};
138
139char _license[] SEC("license") = "GPL";
140u32 _version SEC("version") = 1;