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/82Signed-off-by: K S Iyer <kumar.s.iyer65@gmail.com>
Link: https://patch.msgid.link/20240627-import-bpf-v1-6-0dbcda4a5b1f@kernel.orgSigned-off-by: Benjamin Tissoires <bentiss@kernel.org>

drivers/hid/bpf/progs/Thrustmaster__TCA-Yoke-Boeing.bpf.c

+// 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";