// 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";