IOGEAR__Kaliber-MMOmentum.bpf.c

// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2023 Benjamin Tissoires
 */

#include "vmlinux.h"
#include "hid_bpf.h"
#include "hid_bpf_helpers.h"
#include <bpf/bpf_tracing.h>

#define VID_IOGEAR 0x258A /* VID is shared with SinoWealth and Glorious and prob others */
#define PID_MOMENTUM 0x0027

HID_BPF_CONFIG(
	HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_IOGEAR, PID_MOMENTUM)
);

/*
 * The IOGear Kaliber Gaming MMOmentum Pro mouse has multiple buttons (12)
 * but only 5 are accessible out of the box because the report descriptor
 * marks the other buttons as constants.
 * We just fix the report descriptor to enable those missing 7 buttons.
 */

SEC(HID_BPF_RDESC_FIXUP)
int BPF_PROG(hid_fix_rdesc, struct hid_bpf_ctx *hctx)
{
	const u8 offsets[] = {84, 112, 140};
	__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 4096 /* size */);

	if (!data)
		return 0; /* EPERM check */

	/* if not Keyboard */
	if (data[3] != 0x06)
		return 0;

	for (int idx = 0; idx < ARRAY_SIZE(offsets); idx++) {
		u8 offset = offsets[idx];

		/* if Input (Cnst,Var,Abs) , make it Input (Data,Var,Abs) */
		if (data[offset] == 0x81 && data[offset + 1] == 0x03)
			data[offset + 1] = 0x02;
	}

	return 0;
}

HID_BPF_OPS(iogear_kaliber_momentum) = {
	.hid_rdesc_fixup = (void *)hid_fix_rdesc,
};

SEC("syscall")
int probe(struct hid_bpf_probe_args *ctx)
{
	/* only bind to the keyboard interface */
	ctx->retval = ctx->rdesc_size != 213;
	if (ctx->retval)
		ctx->retval = -EINVAL;

	return 0;
}

char _license[] SEC("license") = "GPL";