HP__Elite-Presenter.bpf.c

 1// SPDX-License-Identifier: GPL-2.0-only
 2/* Copyright (c) 2023 Benjamin Tissoires
 3 */
 4
 5#include "vmlinux.h"
 6#include "hid_bpf.h"
 7#include "hid_bpf_helpers.h"
 8#include <bpf/bpf_tracing.h>
 9
10#define VID_HP 0x03F0
11#define PID_ELITE_PRESENTER 0x464A
12
13HID_BPF_CONFIG(
14	HID_DEVICE(BUS_BLUETOOTH, HID_GROUP_GENERIC, VID_HP, PID_ELITE_PRESENTER)
15);
16
17/*
18 * Already fixed as of commit 0db117359e47 ("HID: add quirk for 03f0:464a
19 * HP Elite Presenter Mouse") in the kernel, but this is a slightly better
20 * fix.
21 *
22 * The HP Elite Presenter Mouse HID Record Descriptor shows
23 * two mice (Report ID 0x1 and 0x2), one keypad (Report ID 0x5),
24 * two Consumer Controls (Report IDs 0x6 and 0x3).
25 * Prior to these fixes it registers one mouse, one keypad
26 * and one Consumer Control, and it was usable only as a
27 * digital laser pointer (one of the two mouses).
28 * We replace the second mouse collection with a pointer collection,
29 * allowing to use the device both as a mouse and a digital laser
30 * pointer.
31 */
32
33SEC(HID_BPF_RDESC_FIXUP)
34int BPF_PROG(hid_fix_rdesc, struct hid_bpf_ctx *hctx)
35{
36	__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 4096 /* size */);
37
38	if (!data)
39		return 0; /* EPERM check */
40
41	/* replace application mouse by application pointer on the second collection */
42	if (data[79] == 0x02)
43		data[79] = 0x01;
44
45	return 0;
46}
47
48HID_BPF_OPS(hp_elite_presenter) = {
49	.hid_rdesc_fixup = (void *)hid_fix_rdesc,
50};
51
52SEC("syscall")
53int probe(struct hid_bpf_probe_args *ctx)
54{
55	ctx->retval = ctx->rdesc_size != 264;
56	if (ctx->retval)
57		ctx->retval = -EINVAL;
58
59	return 0;
60}
61
62char _license[] SEC("license") = "GPL";