// SPDX-License-Identifier: GPL-2.0-only /* Copyright (c) 2025 Red Hat */ #include "vmlinux.h" #include "hid_bpf.h" #include "hid_bpf_helpers.h" #include "hid_report_helpers.h" #include <bpf/bpf_tracing.h> #define VID_UGEE 0x28BD /* VID is shared with SinoWealth and Glorious and prob others */ #define PID_DECO_01_V3 0x0947 HID_BPF_CONFIG( HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_UGEE, PID_DECO_01_V3), ); /* * Default report descriptor reports: * - a report descriptor for the pad buttons, reported as key sequences * - a report descriptor for the pen * - a vendor-specific report descriptor * * The Pad report descriptor, see * https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/issues/54 * * # Report descriptor length: 102 bytes * 0x05, 0x01, // Usage Page (Generic Desktop) 0 * 0x09, 0x02, // Usage (Mouse) 2 * 0xa1, 0x01, // Collection (Application) 4 * 0x85, 0x09, // Report ID (9) 6 * 0x09, 0x01, // Usage (Pointer) 8 * 0xa1, 0x00, // Collection (Physical) 10 * 0x05, 0x09, // Usage Page (Button) 12 * 0x19, 0x01, // UsageMinimum (1) 14 * 0x29, 0x03, // UsageMaximum (3) 16 * 0x15, 0x00, // Logical Minimum (0) 18 * 0x25, 0x01, // Logical Maximum (1) 20 * 0x95, 0x03, // Report Count (3) 22 * 0x75, 0x01, // Report Size (1) 24 * 0x81, 0x02, // Input (Data,Var,Abs) 26 * 0x95, 0x05, // Report Count (5) 28 * 0x81, 0x01, // Input (Cnst,Arr,Abs) 30 * 0x05, 0x01, // Usage Page (Generic Desktop) 32 * 0x09, 0x30, // Usage (X) 34 * 0x09, 0x31, // Usage (Y) 36 * 0x26, 0xff, 0x7f, // Logical Maximum (32767) 38 * 0x95, 0x02, // Report Count (2) 41 * 0x75, 0x10, // Report Size (16) 43 * 0x81, 0x02, // Input (Data,Var,Abs) 45 * 0x05, 0x0d, // Usage Page (Digitizers) 47 * 0x09, 0x30, // Usage (Tip Pressure) 49 * 0x26, 0xff, 0x07, // Logical Maximum (2047) 51 * 0x95, 0x01, // Report Count (1) 54 * 0x75, 0x10, // Report Size (16) 56 * 0x81, 0x02, // Input (Data,Var,Abs) 58 * 0xc0, // End Collection 60 * 0xc0, // End Collection 61 * 0x05, 0x01, // Usage Page (Generic Desktop) 62 * 0x09, 0x06, // Usage (Keyboard) 64 * 0xa1, 0x01, // Collection (Application) 66 * 0x85, 0x06, // Report ID (6) 68 * 0x05, 0x07, // Usage Page (Keyboard/Keypad) 70 * 0x19, 0xe0, // UsageMinimum (224) 72 * 0x29, 0xe7, // UsageMaximum (231) 74 * 0x15, 0x00, // Logical Minimum (0) 76 * 0x25, 0x01, // Logical Maximum (1) 78 * 0x75, 0x01, // Report Size (1) 80 * 0x95, 0x08, // Report Count (8) 82 * 0x81, 0x02, // Input (Data,Var,Abs) 84 * 0x05, 0x07, // Usage Page (Keyboard/Keypad) 86 * 0x19, 0x00, // UsageMinimum (0) 88 * 0x29, 0xff, // UsageMaximum (255) 90 * 0x26, 0xff, 0x00, // Logical Maximum (255) 92 * 0x75, 0x08, // Report Size (8) 95 * 0x95, 0x06, // Report Count (6) 97 * 0x81, 0x00, // Input (Data,Arr,Abs) 99 * 0xc0, // End Collection 101 * * And key events for buttons top->bottom are: * Buttons released: 06 00 00 00 00 00 00 00 * Button1: 06 00 05 00 00 00 00 00 -> b * Button2: 06 00 08 00 00 00 00 00 -> e * Button3: 06 04 00 00 00 00 00 00 -> LAlt * Button4: 06 00 2c 00 00 00 00 00 -> Space * Button5: 06 01 16 00 00 00 00 00 -> LControl + s * Button6: 06 01 1d 00 00 00 00 00 -> LControl + z * Button7: 06 01 57 00 00 00 00 00 -> LControl + Keypad Plus * Button8: 06 01 56 00 00 00 00 00 -> LControl + Keypad Dash * * When multiple buttons are pressed at the same time, the values used to * identify the buttons are identical, but they appear in different bytes of the * record. For example, when button 2 (0x08) and button 1 (0x05) are pressed, * this is the report: * * Buttons 2 and 1: 06 00 08 05 00 00 00 00 -> e + b * * Buttons 1, 2, 4, 5 and 6 can be matched by finding their values in the * report. * * Button 3 is pressed when the 3rd bit is 1. For example, pressing buttons 3 * and 5 generates this report: * * Buttons 3 and 5: 06 05 16 00 00 00 00 00 -> LControl + LAlt + s * -- -- * | | * | `- Button 5 (0x16) * `- 0x05 = 0101. Button 3 is pressed * ^ * * pad_buttons contains a list of buttons that can be matched in * HID_BPF_DEVICE_EVENT. Button 3 as it has a dedicated bit. * * * The Pen report descriptor announces a wrong tilt range: * * Report descriptor length: 109 bytes * 0x05, 0x0d, // Usage Page (Digitizers) 0 * 0x09, 0x02, // Usage (Pen) 2 * 0xa1, 0x01, // Collection (Application) 4 * 0x85, 0x07, // Report ID (7) 6 * 0x09, 0x20, // Usage (Stylus) 8 * 0xa1, 0x01, // Collection (Application) 10 * 0x09, 0x42, // Usage (Tip Switch) 12 * 0x09, 0x44, // Usage (Barrel Switch) 14 * 0x09, 0x45, // Usage (Eraser) 16 * 0x09, 0x3c, // Usage (Invert) 18 * 0x15, 0x00, // Logical Minimum (0) 20 * 0x25, 0x01, // Logical Maximum (1) 22 * 0x75, 0x01, // Report Size (1) 24 * 0x95, 0x04, // Report Count (4) 26 * 0x81, 0x02, // Input (Data,Var,Abs) 28 * 0x95, 0x01, // Report Count (1) 30 * 0x81, 0x03, // Input (Cnst,Var,Abs) 32 * 0x09, 0x32, // Usage (In Range) 34 * 0x95, 0x01, // Report Count (1) 36 * 0x81, 0x02, // Input (Data,Var,Abs) 38 * 0x95, 0x02, // Report Count (2) 40 * 0x81, 0x03, // Input (Cnst,Var,Abs) 42 * 0x75, 0x10, // Report Size (16) 44 * 0x95, 0x01, // Report Count (1) 46 * 0x35, 0x00, // Physical Minimum (0) 48 * 0xa4, // Push 50 * 0x05, 0x01, // Usage Page (Generic Desktop) 51 * 0x09, 0x30, // Usage (X) 53 * 0x65, 0x13, // Unit (EnglishLinear: in) 55 * 0x55, 0x0d, // Unit Exponent (-3) 57 * 0x46, 0x10, 0x27, // Physical Maximum (10000) 59 * 0x26, 0xff, 0x7f, // Logical Maximum (32767) 62 * 0x81, 0x02, // Input (Data,Var,Abs) 65 * 0x09, 0x31, // Usage (Y) 67 * 0x46, 0x6a, 0x18, // Physical Maximum (6250) 69 * 0x26, 0xff, 0x7f, // Logical Maximum (32767) 72 * 0x81, 0x02, // Input (Data,Var,Abs) 75 * 0xb4, // Pop 77 * 0x09, 0x30, // Usage (X) 78 * 0x45, 0x00, // Physical Maximum (0) 80 * 0x26, 0xff, 0x3f, // Logical Maximum (16383) 82 * 0x81, 0x42, // Input (Data,Var,Abs,Null) 85 * 0x09, 0x3d, // Usage (Start) 87 * 0x15, 0x81, // Logical Minimum (-127) 89 <- Change from -127 to -60 * 0x25, 0x7f, // Logical Maximum (127) 91 <- Change from 127 to 60 * 0x75, 0x08, // Report Size (8) 93 * 0x95, 0x01, // Report Count (1) 95 * 0x81, 0x02, // Input (Data,Var,Abs) 97 * 0x09, 0x3e, // Usage (Select) 99 * 0x15, 0x81, // Logical Minimum (-127) 101 <- Change from -127 to -60 * 0x25, 0x7f, // Logical Maximum (127) 103 <- Change from 127 to 60 * 0x81, 0x02, // Input (Data,Var,Abs) 105 * 0xc0, // End Collection 107 * 0xc0, // End Collection 108 */ #define PEN_REPORT_DESCRIPTOR_LENGTH 109 #define PAD_REPORT_DESCRIPTOR_LENGTH 102 #define PAD_REPORT_LENGTH 8 #define PAD_REPORT_ID 6 #define PAD_NUM_BUTTONS 8 static const __u8 fixed_rdesc_pad[] = { UsagePage_GenericDesktop Usage_GD_Keypad CollectionApplication( // Byte 0 in report is the report ID ReportId(PAD_REPORT_ID) ReportCount(1) ReportSize(8) UsagePage_Digitizers Usage_Dig_TabletFunctionKeys CollectionPhysical( // Byte 1 is the button state UsagePage_Button UsageMinimum_i8(0x01) UsageMaximum_i8(PAD_NUM_BUTTONS) LogicalMinimum_i8(0x0) LogicalMaximum_i8(0x1) ReportCount(PAD_NUM_BUTTONS) ReportSize(1) Input(Var|Abs) // Byte 2 in report - just exists so we get to be a tablet pad UsagePage_Digitizers Usage_Dig_BarrelSwitch // BTN_STYLUS ReportCount(1) ReportSize(1) Input(Var|Abs) ReportCount(7) // padding Input(Const) // Bytes 3/4 in report - just exists so we get to be a tablet pad UsagePage_GenericDesktop Usage_GD_X Usage_GD_Y ReportCount(2) ReportSize(8) Input(Var|Abs) // Byte 5-7 are padding so we match the original report lengtth ReportCount(3) ReportSize(8) Input(Const) ) ) }; SEC(HID_BPF_RDESC_FIXUP) int BPF_PROG(xppen_deco01v3_rdesc_fixup, struct hid_bpf_ctx *hctx) { __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, HID_MAX_DESCRIPTOR_SIZE /* size */); const __u8 wrong_logical_range[] = {0x15, 0x81, 0x25, 0x7f}; const __u8 correct_logical_range[] = {0x15, 0xc4, 0x25, 0x3c}; if (!data) return 0; /* EPERM check */ switch (hctx->size) { case PAD_REPORT_DESCRIPTOR_LENGTH: __builtin_memcpy(data, fixed_rdesc_pad, sizeof(fixed_rdesc_pad)); return sizeof(fixed_rdesc_pad); case PEN_REPORT_DESCRIPTOR_LENGTH: if (__builtin_memcmp(&data[89], wrong_logical_range, sizeof(wrong_logical_range)) == 0) __builtin_memcpy(&data[89], correct_logical_range, sizeof(correct_logical_range)); if (__builtin_memcmp(&data[101], wrong_logical_range, sizeof(wrong_logical_range)) == 0) __builtin_memcpy(&data[101], correct_logical_range, sizeof(correct_logical_range)); break; } return 0; } SEC(HID_BPF_DEVICE_EVENT) int BPF_PROG(xppen_deco01v3_device_event, struct hid_bpf_ctx *hctx) { static const __u8 pad_buttons[] = { 0x05, 0x08, 0x00, 0x2c, 0x16, 0x1d, 0x57, 0x56 }; __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, PAD_REPORT_LENGTH /* size */); if (!data) return 0; /* EPERM check */ if (data[0] == PAD_REPORT_ID) { __u8 button_mask = 0; size_t d, b; /* data[1] stores the status of BTN_2 in the 3rd bit*/ if (data[1] & BIT(2)) button_mask |= BIT(2); /* The rest of the descriptor stores the buttons as in pad_buttons */ for (d = 2; d < 8; d++) { for (b = 0; b < sizeof(pad_buttons); b++) { if (data[d] != 0 && data[d] == pad_buttons[b]) button_mask |= BIT(b); } } __u8 report[8] = {PAD_REPORT_ID, button_mask, 0x00}; __builtin_memcpy(data, report, sizeof(report)); } return 0; } HID_BPF_OPS(xppen_deco01v3) = { .hid_rdesc_fixup = (void *)xppen_deco01v3_rdesc_fixup, .hid_device_event = (void *)xppen_deco01v3_device_event, }; SEC("syscall") int probe(struct hid_bpf_probe_args *ctx) { switch (ctx->rdesc_size) { case PAD_REPORT_DESCRIPTOR_LENGTH: case PEN_REPORT_DESCRIPTOR_LENGTH: ctx->retval = 0; break; default: ctx->retval = -EINVAL; } return 0; } char _license[] SEC("license") = "GPL";
