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1// SPDX-License-Identifier: GPL-2.0-only2/* Copyright (c) 2024 Kumar Swarnam Iyer (kumar.s.iyer65@gmail.com)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_THRUSTMASTER 0x044F11#define PID_TCA_YOKE_BOEING 0x040912 13HID_BPF_CONFIG(14 HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_THRUSTMASTER, PID_TCA_YOKE_BOEING)15);16 17/* The original HID descriptor of the Thrustmaster TCA Yoke Boeing joystick contains18 * an Input field that shows up as an axis, ABS_MISC in Linux. But it is not possible19 * to assign an actual physical control to this axis as they're all taken up. There20 * are 2 vendor-defined inputs where the Input type appears to be defined wrongly.21 * This bpf attempts to fix this by changing the Inputs so that it doesn't show up in22 * Linux at all.23 * This version is the short version fix that only changes 2 fields in the descriptor24 * instead of the whole report descriptor.25 * For reference, this is the original report descriptor:26 *27 * 0x05, 0x01, // Usage Page (Generic Desktop) 028 * 0x09, 0x04, // Usage (Joystick) 229 * 0xa1, 0x01, // Collection (Application) 430 * 0x85, 0x01, // Report ID (1) 631 * 0x09, 0x39, // Usage (Hat switch) 832 * 0x15, 0x00, // Logical Minimum (0) 1033 * 0x25, 0x07, // Logical Maximum (7) 1234 * 0x35, 0x00, // Physical Minimum (0) 1435 * 0x46, 0x3b, 0x01, // Physical Maximum (315) 1636 * 0x65, 0x14, // Unit (EnglishRotation: deg) 1937 * 0x75, 0x04, // Report Size (4) 2138 * 0x95, 0x01, // Report Count (1) 2339 * 0x81, 0x42, // Input (Data,Var,Abs,Null) 2540 * 0x65, 0x00, // Unit (None) 2741 * 0x05, 0x09, // Usage Page (Button) 2942 * 0x19, 0x01, // Usage Minimum (1) 3143 * 0x29, 0x12, // Usage Maximum (18) 3344 * 0x15, 0x00, // Logical Minimum (0) 3545 * 0x25, 0x01, // Logical Maximum (1) 3746 * 0x75, 0x01, // Report Size (1) 3947 * 0x95, 0x12, // Report Count (18) 4148 * 0x81, 0x02, // Input (Data,Var,Abs) 4349 * 0x95, 0x02, // Report Count (2) 4550 * 0x81, 0x03, // Input (Cnst,Var,Abs) 4751 * 0x05, 0x01, // Usage Page (Generic Desktop) 4952 * 0x09, 0x31, // Usage (Y) 5153 * 0x09, 0x30, // Usage (X) 5354 * 0x09, 0x32, // Usage (Z) 5555 * 0x09, 0x34, // Usage (Ry) 5756 * 0x09, 0x33, // Usage (Rx) 5957 * 0x09, 0x35, // Usage (Rz) 6158 * 0x15, 0x00, // Logical Minimum (0) 6359 * 0x27, 0xff, 0xff, 0x00, 0x00, // Logical Maximum (65535) 6560 * 0x75, 0x10, // Report Size (16) 7061 * 0x95, 0x06, // Report Count (6) 7262 * 0x81, 0x02, // Input (Data,Var,Abs) 7463 * 0x06, 0xf0, 0xff, // Usage Page (Vendor Usage Page 0xfff0) 7664 * 0x09, 0x59, // Usage (Vendor Usage 0x59) 7965 * 0x15, 0x00, // Logical Minimum (0) 8166 * 0x26, 0xff, 0x00, // Logical Maximum (255) 8367 * 0x75, 0x08, // Report Size (8) 8668 * 0x95, 0x01, // Report Count (1) 8869 * 0x81, 0x02, // Input (Data,Var,Abs) 90 --> Needs to be changed70 * 0x09, 0x51, // Usage (Vendor Usage 0x51) 9271 * 0x15, 0x00, // Logical Minimum (0) 9472 * 0x26, 0xff, 0x00, // Logical Maximum (255) 9673 * 0x75, 0x08, // Report Size (8) 9974 * 0x95, 0x20, // Report Count (32) 101 --> Needs to be changed75 * 0x81, 0x02, // Input (Data,Var,Abs) 10376 * 0x09, 0x50, // Usage (Vendor Usage 0x50) 10577 * 0x15, 0x00, // Logical Minimum (0) 10778 * 0x26, 0xff, 0x00, // Logical Maximum (255) 10979 * 0x75, 0x08, // Report Size (8) 11280 * 0x95, 0x0f, // Report Count (15) 11481 * 0x81, 0x03, // Input (Cnst,Var,Abs) 11682 * 0x09, 0x47, // Usage (Vendor Usage 0x47) 11883 * 0x85, 0xf2, // Report ID (242) 12084 * 0x15, 0x00, // Logical Minimum (0) 12285 * 0x26, 0xff, 0x00, // Logical Maximum (255) 12486 * 0x75, 0x08, // Report Size (8) 12787 * 0x95, 0x3f, // Report Count (63) 12988 * 0xb1, 0x02, // Feature (Data,Var,Abs) 13189 * 0x09, 0x48, // Usage (Vendor Usage 0x48) 13390 * 0x85, 0xf3, // Report ID (243) 13591 * 0x15, 0x00, // Logical Minimum (0) 13792 * 0x26, 0xff, 0x00, // Logical Maximum (255) 13993 * 0x75, 0x08, // Report Size (8) 14294 * 0x95, 0x3f, // Report Count (63) 14495 * 0xb1, 0x02, // Feature (Data,Var,Abs) 14696 * 0xc0, // End Collection 14897 */98 99SEC(HID_BPF_RDESC_FIXUP)100int BPF_PROG(hid_fix_rdesc_tca_yoke, struct hid_bpf_ctx *hctx)101{102 const int expected_length = 148;103 104 if (hctx->size != expected_length)105 return 0;106 107 __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, HID_MAX_DESCRIPTOR_SIZE /* size */);108 109 if (!data)110 return 0; /* EPERM */111 112 /* Safety check, our probe() should take care of this though */113 if (data[1] != 0x01 /* Generic Desktop */ || data[3] != 0x04 /* Joystick */)114 return 0;115 116 /* The report descriptor sets incorrect Input items in 2 places, resulting in a117 * non-existing axis showing up.118 * This change sets the correct Input which prevents the axis from showing up in Linux.119 */120 121 if (data[90] == 0x81 && /* Input */122 data[103] == 0x81) { /* Input */123 data[91] = 0x03; /* Input set to 0x03 Constant, Variable Absolute */124 data[104] = 0x03; /* Input set to 0X03 Constant, Variable Absolute */125 }126 127 return 0;128}129 130HID_BPF_OPS(tca_yoke) = {131 .hid_rdesc_fixup = (void *)hid_fix_rdesc_tca_yoke,132};133 134SEC("syscall")135int probe(struct hid_bpf_probe_args *ctx)136{137 /* ensure the kernel isn't fixed already */138 if (ctx->rdesc[91] != 0x02) /* Input for 0x59 Usage type has changed */139 ctx->retval = -EINVAL;140 141 return 0;142}143 144char _license[] SEC("license") = "GPL";145