| // SPDX-License-Identifier: GPL-2.0-only |
| /* Copyright (c) 2024 Kumar Swarnam Iyer (kumar.s.iyer65@gmail.com) |
| */ |
| |
| #include "vmlinux.h" |
| #include "hid_bpf.h" |
| #include "hid_bpf_helpers.h" |
| #include <bpf/bpf_tracing.h> |
| |
| #define VID_THRUSTMASTER 0x044F |
| #define PID_TCA_YOKE_BOEING 0x0409 |
| |
| HID_BPF_CONFIG( |
| HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_THRUSTMASTER, PID_TCA_YOKE_BOEING) |
| ); |
| |
| /* The original HID descriptor of the Thrustmaster TCA Yoke Boeing joystick contains |
| * an Input field that shows up as an axis, ABS_MISC in Linux. But it is not possible |
| * to assign an actual physical control to this axis as they're all taken up. There |
| * are 2 vendor-defined inputs where the Input type appears to be defined wrongly. |
| * This bpf attempts to fix this by changing the Inputs so that it doesn't show up in |
| * Linux at all. |
| * This version is the short version fix that only changes 2 fields in the descriptor |
| * instead of the whole report descriptor. |
| * For reference, this is the original report descriptor: |
| * |
| * 0x05, 0x01, // Usage Page (Generic Desktop) 0 |
| * 0x09, 0x04, // Usage (Joystick) 2 |
| * 0xa1, 0x01, // Collection (Application) 4 |
| * 0x85, 0x01, // Report ID (1) 6 |
| * 0x09, 0x39, // Usage (Hat switch) 8 |
| * 0x15, 0x00, // Logical Minimum (0) 10 |
| * 0x25, 0x07, // Logical Maximum (7) 12 |
| * 0x35, 0x00, // Physical Minimum (0) 14 |
| * 0x46, 0x3b, 0x01, // Physical Maximum (315) 16 |
| * 0x65, 0x14, // Unit (EnglishRotation: deg) 19 |
| * 0x75, 0x04, // Report Size (4) 21 |
| * 0x95, 0x01, // Report Count (1) 23 |
| * 0x81, 0x42, // Input (Data,Var,Abs,Null) 25 |
| * 0x65, 0x00, // Unit (None) 27 |
| * 0x05, 0x09, // Usage Page (Button) 29 |
| * 0x19, 0x01, // Usage Minimum (1) 31 |
| * 0x29, 0x12, // Usage Maximum (18) 33 |
| * 0x15, 0x00, // Logical Minimum (0) 35 |
| * 0x25, 0x01, // Logical Maximum (1) 37 |
| * 0x75, 0x01, // Report Size (1) 39 |
| * 0x95, 0x12, // Report Count (18) 41 |
| * 0x81, 0x02, // Input (Data,Var,Abs) 43 |
| * 0x95, 0x02, // Report Count (2) 45 |
| * 0x81, 0x03, // Input (Cnst,Var,Abs) 47 |
| * 0x05, 0x01, // Usage Page (Generic Desktop) 49 |
| * 0x09, 0x31, // Usage (Y) 51 |
| * 0x09, 0x30, // Usage (X) 53 |
| * 0x09, 0x32, // Usage (Z) 55 |
| * 0x09, 0x34, // Usage (Ry) 57 |
| * 0x09, 0x33, // Usage (Rx) 59 |
| * 0x09, 0x35, // Usage (Rz) 61 |
| * 0x15, 0x00, // Logical Minimum (0) 63 |
| * 0x27, 0xff, 0xff, 0x00, 0x00, // Logical Maximum (65535) 65 |
| * 0x75, 0x10, // Report Size (16) 70 |
| * 0x95, 0x06, // Report Count (6) 72 |
| * 0x81, 0x02, // Input (Data,Var,Abs) 74 |
| * 0x06, 0xf0, 0xff, // Usage Page (Vendor Usage Page 0xfff0) 76 |
| * 0x09, 0x59, // Usage (Vendor Usage 0x59) 79 |
| * 0x15, 0x00, // Logical Minimum (0) 81 |
| * 0x26, 0xff, 0x00, // Logical Maximum (255) 83 |
| * 0x75, 0x08, // Report Size (8) 86 |
| * 0x95, 0x01, // Report Count (1) 88 |
| * 0x81, 0x02, // Input (Data,Var,Abs) 90 --> Needs to be changed |
| * 0x09, 0x51, // Usage (Vendor Usage 0x51) 92 |
| * 0x15, 0x00, // Logical Minimum (0) 94 |
| * 0x26, 0xff, 0x00, // Logical Maximum (255) 96 |
| * 0x75, 0x08, // Report Size (8) 99 |
| * 0x95, 0x20, // Report Count (32) 101 --> Needs to be changed |
| * 0x81, 0x02, // Input (Data,Var,Abs) 103 |
| * 0x09, 0x50, // Usage (Vendor Usage 0x50) 105 |
| * 0x15, 0x00, // Logical Minimum (0) 107 |
| * 0x26, 0xff, 0x00, // Logical Maximum (255) 109 |
| * 0x75, 0x08, // Report Size (8) 112 |
| * 0x95, 0x0f, // Report Count (15) 114 |
| * 0x81, 0x03, // Input (Cnst,Var,Abs) 116 |
| * 0x09, 0x47, // Usage (Vendor Usage 0x47) 118 |
| * 0x85, 0xf2, // Report ID (242) 120 |
| * 0x15, 0x00, // Logical Minimum (0) 122 |
| * 0x26, 0xff, 0x00, // Logical Maximum (255) 124 |
| * 0x75, 0x08, // Report Size (8) 127 |
| * 0x95, 0x3f, // Report Count (63) 129 |
| * 0xb1, 0x02, // Feature (Data,Var,Abs) 131 |
| * 0x09, 0x48, // Usage (Vendor Usage 0x48) 133 |
| * 0x85, 0xf3, // Report ID (243) 135 |
| * 0x15, 0x00, // Logical Minimum (0) 137 |
| * 0x26, 0xff, 0x00, // Logical Maximum (255) 139 |
| * 0x75, 0x08, // Report Size (8) 142 |
| * 0x95, 0x3f, // Report Count (63) 144 |
| * 0xb1, 0x02, // Feature (Data,Var,Abs) 146 |
| * 0xc0, // End Collection 148 |
| */ |
| |
| SEC(HID_BPF_RDESC_FIXUP) |
| int BPF_PROG(hid_fix_rdesc_tca_yoke, struct hid_bpf_ctx *hctx) |
| { |
| const int expected_length = 148; |
| |
| if (hctx->size != expected_length) |
| return 0; |
| |
| __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, HID_MAX_DESCRIPTOR_SIZE /* size */); |
| |
| if (!data) |
| return 0; /* EPERM */ |
| |
| /* Safety check, our probe() should take care of this though */ |
| if (data[1] != 0x01 /* Generic Desktop */ || data[3] != 0x04 /* Joystick */) |
| return 0; |
| |
| /* The report descriptor sets incorrect Input items in 2 places, resulting in a |
| * non-existing axis showing up. |
| * This change sets the correct Input which prevents the axis from showing up in Linux. |
| */ |
| |
| if (data[90] == 0x81 && /* Input */ |
| data[103] == 0x81) { /* Input */ |
| data[91] = 0x03; /* Input set to 0x03 Constant, Variable Absolute */ |
| data[104] = 0x03; /* Input set to 0X03 Constant, Variable Absolute */ |
| } |
| |
| return 0; |
| } |
| |
| HID_BPF_OPS(tca_yoke) = { |
| .hid_rdesc_fixup = (void *)hid_fix_rdesc_tca_yoke, |
| }; |
| |
| SEC("syscall") |
| int probe(struct hid_bpf_probe_args *ctx) |
| { |
| /* ensure the kernel isn't fixed already */ |
| if (ctx->rdesc[91] != 0x02) /* Input for 0x59 Usage type has changed */ |
| ctx->retval = -EINVAL; |
| |
| return 0; |
| } |
| |
| char _license[] SEC("license") = "GPL"; |
