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// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2025 Curran Muhlberger
*/
#include "vmlinux.h"
#include "hid_bpf.h"
#include "hid_bpf_helpers.h"
#include <bpf/bpf_tracing.h>
#define VID_LOGITECH 0x046D
#define PID_SPACENAVIGATOR 0xC626
HID_BPF_CONFIG(
HID_DEVICE(BUS_USB, HID_GROUP_ANY, VID_LOGITECH, PID_SPACENAVIGATOR)
);
/*
* The 3Dconnexion SpaceNavigator 3D Mouse is a multi-axis controller with 6
* axes (grouped as X,Y,Z and Rx,Ry,Rz). Axis data is absolute, but the report
* descriptor erroneously declares it to be relative. We fix the report
* descriptor to mark both axis collections as absolute.
*
* The kernel attempted to fix this in commit 24985cf68612 (HID: support
* Logitech/3DConnexion SpaceTraveler and SpaceNavigator), but the descriptor
* data offsets are incorrect for at least some SpaceNavigator units.
*/
SEC(HID_BPF_RDESC_FIXUP)
int BPF_PROG(hid_fix_rdesc, struct hid_bpf_ctx *hctx)
{
__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 4096 /* size */);
if (!data)
return 0; /* EPERM check */
/* Offset of Input item in X,Y,Z and Rx,Ry,Rz collections for all known
* firmware variants.
* - 2009 model: X,Y,Z @ 32-33, Rx,Ry,Rz @ 49-50 (fixup originally
* applied in kernel)
* - 2016 model (size==228): X,Y,Z @ 36-37, Rx,Ry,Rz @ 53-54
*
* The descriptor size of the 2009 model is not known, and there is evidence
* for at least two other variants (with sizes 202 & 217) besides the 2016
* model, so we try all known offsets regardless of descriptor size.
*/
const u8 offsets[] = {32, 36, 49, 53};
for (size_t idx = 0; idx < ARRAY_SIZE(offsets); idx++) {
u8 offset = offsets[idx];
/* if Input (Data,Var,Rel) , make it Input (Data,Var,Abs) */
if (data[offset] == 0x81 && data[offset + 1] == 0x06)
data[offset + 1] = 0x02;
}
return 0;
}
HID_BPF_OPS(logitech_spacenavigator) = {
.hid_rdesc_fixup = (void *)hid_fix_rdesc,
};
SEC("syscall")
int probe(struct hid_bpf_probe_args *ctx)
{
/* Ensure report descriptor size matches one of the known variants. */
if (ctx->rdesc_size != 202 &&
ctx->rdesc_size != 217 &&
ctx->rdesc_size != 228) {
ctx->retval = -EINVAL;
return 0;
}
/* Check whether the kernel has already applied the fix. */
if ((ctx->rdesc[32] == 0x81 && ctx->rdesc[33] == 0x02 &&
ctx->rdesc[49] == 0x81 && ctx->rdesc[50] == 0x02) ||
(ctx->rdesc[36] == 0x81 && ctx->rdesc[37] == 0x02 &&
ctx->rdesc[53] == 0x81 && ctx->rdesc[54] == 0x02))
ctx->retval = -EINVAL;
else
ctx->retval = 0;
return 0;
}
char _license[] SEC("license") = "GPL";
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