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Benjamin Tissoires
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HID: bpf: Thrustmaster TCA Yoke Boeing joystick fix
This joystick's original HID descriptor is wrong & it shows a ABS_MISC axis in Linux that doesn't exist on the hardware. Link: https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/82 Signed-off-by: K S Iyer <[email protected]> Link: https://patch.msgid.link/[email protected] Signed-off-by: Benjamin Tissoires <[email protected]>
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‎drivers/hid/bpf/progs/Thrustmaster__TCA-Yoke-Boeing.bpf.c

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

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