// SPDX-License-Identifier: GPL-2.0-only #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 #define PID_DECO_02 0x0803 HID_BPF_CONFIG( HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_UGEE, PID_DECO_02), ); /* * Devices are: * - Pad input, including pen (This is the only one we are interested in) * - Pen input as mouse * - Vendor * * Descriptors on main device are: * - 7: Pen * - 6: Vendor settings? Unclear * - 3: Keyboard (This is what we want to modify) * - 5: Feature report * * This creates three event nodes: * - XP-PEN DECO 02 Stylus * - XP-PEN DECO 02 * - XP-PEN DECO 02 Keyboard (Again, what we want to modify) * * # Report descriptor length: 188 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, 0x00, // Collection (Physical) 10 * # 0x09, 0x42, // Usage (Tip Switch) 12 * # 0x09, 0x44, // Usage (Barrel Switch) 14 * # 0x09, 0x45, // Usage (Eraser) 16 * # 0x09, 0x3c, // Usage (Invert) 18 * # 0x09, 0x32, // Usage (In Range) 20 * # 0x15, 0x00, // Logical Minimum (0) 22 * # 0x25, 0x01, // Logical Maximum (1) 24 * # 0x75, 0x01, // Report Size (1) 26 * # 0x95, 0x05, // Report Count (5) 28 * # 0x81, 0x02, // Input (Data,Var,Abs) 30 * # 0x95, 0x03, // Report Count (3) 32 * # 0x81, 0x03, // Input (Cnst,Var,Abs) 34 * # 0x05, 0x01, // Usage Page (Generic Desktop) 36 * # 0x09, 0x30, // Usage (X) 38 * # 0x15, 0x00, // Logical Minimum (0) 40 * # 0x26, 0x50, 0x57, // Logical Maximum (22352) 42 * # 0x55, 0x0d, // Unit Exponent (-3) 45 * # 0x65, 0x13, // Unit (EnglishLinear: in) 47 * # 0x35, 0x00, // Physical Minimum (0) 49 * # 0x46, 0x50, 0x57, // Physical Maximum (22352) 51 * # 0x75, 0x10, // Report Size (16) 54 * # 0x95, 0x01, // Report Count (1) 56 * # 0x81, 0x02, // Input (Data,Var,Abs) 58 * # 0x09, 0x31, // Usage (Y) 60 * # 0x15, 0x00, // Logical Minimum (0) 62 * # 0x26, 0x92, 0x36, // Logical Maximum (13970) 64 * # 0x55, 0x0d, // Unit Exponent (-3) 67 * # 0x65, 0x13, // Unit (EnglishLinear: in) 69 * # 0x35, 0x00, // Physical Minimum (0) 71 * # 0x46, 0x92, 0x36, // Physical Maximum (13970) 73 * # 0x75, 0x10, // Report Size (16) 76 * # 0x95, 0x01, // Report Count (1) 78 * # 0x81, 0x02, // Input (Data,Var,Abs) 80 * # 0x05, 0x0d, // Usage Page (Digitizers) 82 * # 0x09, 0x30, // Usage (Tip Pressure) 84 * # 0x15, 0x00, // Logical Minimum (0) 86 * # 0x26, 0xff, 0x1f, // Logical Maximum (8191) 88 * # 0x75, 0x10, // Report Size (16) 91 * # 0x95, 0x01, // Report Count (1) 93 * # 0x81, 0x02, // Input (Data,Var,Abs) 95 * # 0xc0, // End Collection 97 * # 0xc0, // End Collection 98 * # 0x09, 0x0e, // Usage (Device Configuration) 99 * # 0xa1, 0x01, // Collection (Application) 101 * # 0x85, 0x05, // Report ID (5) 103 * # 0x09, 0x23, // Usage (Device Settings) 105 * # 0xa1, 0x02, // Collection (Logical) 107 * # 0x09, 0x52, // Usage (Inputmode) 109 * # 0x09, 0x53, // Usage (Device Index) 111 * # 0x25, 0x0a, // Logical Maximum (10) 113 * # 0x75, 0x08, // Report Size (8) 115 * # 0x95, 0x02, // Report Count (2) 117 * # 0xb1, 0x02, // Feature (Data,Var,Abs) 119 * # 0xc0, // End Collection 121 * # 0xc0, // End Collection 122 * # 0x05, 0x0c, // Usage Page (Consumer Devices) 123 * # 0x09, 0x36, // Usage (Function Buttons) 125 * # 0xa1, 0x00, // Collection (Physical) 127 * # 0x85, 0x06, // Report ID (6) 129 * # 0x05, 0x09, // Usage Page (Button) 131 * # 0x19, 0x01, // Usage Minimum (1) 133 * # 0x29, 0x20, // Usage Maximum (32) 135 * # 0x15, 0x00, // Logical Minimum (0) 137 * # 0x25, 0x01, // Logical Maximum (1) 139 * # 0x95, 0x20, // Report Count (32) 141 * # 0x75, 0x01, // Report Size (1) 143 * # 0x81, 0x02, // Input (Data,Var,Abs) 145 * # 0xc0, // End Collection 147 * # 0x05, 0x01, // Usage Page (Generic Desktop) 148 * # 0x09, 0x06, // Usage (Keyboard) 150 * # 0xa1, 0x01, // Collection (Application) 152 * # 0x85, 0x03, // Report ID (3) 154 * # 0x05, 0x07, // Usage Page (Keyboard) 156 * # 0x19, 0xe0, // Usage Minimum (224) 158 * # 0x29, 0xe7, // Usage Maximum (231) 160 * # 0x15, 0x00, // Logical Minimum (0) 162 * # 0x25, 0x01, // Logical Maximum (1) 164 * # 0x75, 0x01, // Report Size (1) 166 * # 0x95, 0x08, // Report Count (8) 168 * # 0x81, 0x02, // Input (Data,Var,Abs) 170 * # 0x05, 0x07, // Usage Page (Keyboard) 172 * # 0x19, 0x00, // Usage Minimum (0) 174 * # 0x29, 0xff, // Usage Maximum (255) 176 * # 0x26, 0xff, 0x00, // Logical Maximum (255) 178 * # 0x75, 0x08, // Report Size (8) 181 * # 0x95, 0x06, // Report Count (6) 183 * # 0x81, 0x00, // Input (Data,Arr,Abs) 185 * # 0xc0, // End Collection 187 * * Key events; top to bottom: * Buttons released: 03 00 00 00 00 00 00 00 * Button1: 03 00 05 00 00 00 00 00 -> 'b and B' * Button2: 03 00 2c 00 00 00 00 00 -> 'Spacebar' * Button3: 03 00 08 00 00 00 00 00 -> 'e and E' * Button4: 03 00 0c 00 00 00 00 00 -> 'i and I' * Button5: 03 05 1d 00 00 00 00 00 -> LeftControl + LeftAlt + 'z and Z' * Button6: 03 01 16 00 00 00 00 00 -> LeftControl + 's and S' * * Dial Events: * Clockwise: 03 01 2e 00 00 00 00 00 -> LeftControl + '= and +' * Anticlockwise: 03 01 2d 00 00 00 00 00 -> LeftControl + '- and (underscore)' * * NOTE: Input event descriptions begin at byte 2, and progressively build * towards byte 7 as each new key is pressed maintaining the press order. * For example: * BTN1 followed by BTN2 is 03 00 05 2c 00 00 00 00 * BTN2 followed by BTN1 is 03 00 2c 05 00 00 00 00 * * Releasing a button causes its byte to be freed, and the next item in the list * is pushed forwards. Dial events are released immediately after an event is * registered (i.e. after each "click"), so will continually appear pushed * backwards in the report. * * When a button with a modifier key is pressed, the button identifier stacks in * an abnormal way, where the highest modifier byte always supersedes others. * In these cases, the button with the higher modifier is always last. * For example: * BTN6 followed by BTN5 is 03 05 1d 16 00 00 00 00 * BTN5 followed by BTN6 is 03 05 1d 16 00 00 00 00 * BTN5 followed by BTN1 is 03 05 05 1d 00 00 00 00 * * For three button presses in order, demonstrating strictly above rules: * BTN6, BTN1, BTN5 is 03 05 05 1d 16 00 00 00 * BTN5, BTN1, BTN6 is 03 05 05 1d 16 00 00 00 * * In short, when BTN5/6 are pressed, the order of operations is lost, as they * will always float to the end when pressed in combination with others. * * Fortunately, all states are recorded in the same way, with no overlaps. * Byte 1 can be used as a spare for the wheel, since this is for mod keys. */ #define RDESC_SIZE_PAD 188 #define REPORT_SIZE_PAD 8 #define REPORT_ID_BUTTONS 3 #define PAD_BUTTON_COUNT 6 #define RDESC_KEYBOARD_OFFSET 148 static const __u8 fixed_rdesc_pad[] = { /* Copy of pen descriptor to avoid losing functionality */ UsagePage_Digitizers Usage_Dig_Pen CollectionApplication( ReportId(7) Usage_Dig_Stylus CollectionPhysical( Usage_Dig_TipSwitch Usage_Dig_BarrelSwitch Usage_Dig_Eraser Usage_Dig_Invert Usage_Dig_InRange LogicalMinimum_i8(0) LogicalMaximum_i8(1) ReportSize(1) ReportCount(5) Input(Var|Abs) ReportCount(3) Input(Const) /* Input (Const, Var, Abs) */ UsagePage_GenericDesktop Usage_GD_X LogicalMinimum_i16(0) LogicalMaximum_i16(22352) UnitExponent(-3) Unit(in) /* (EnglishLinear: in) */ PhysicalMinimum_i16(0) PhysicalMaximum_i16(22352) ReportSize(16) ReportCount(1) Input(Var|Abs) Usage_GD_Y LogicalMinimum_i16(0) LogicalMaximum_i16(13970) UnitExponent(-3) Unit(in) /* (EnglishLinear: in) */ PhysicalMinimum_i16(0) PhysicalMaximum_i16(13970) ReportSize(16) ReportCount(1) Input(Var|Abs) UsagePage_Digitizers Usage_Dig_TipPressure LogicalMinimum_i16(0) LogicalMaximum_i16(8191) ReportSize(16) ReportCount(1) Input(Var|Abs) ) ) /* FIXES BEGIN */ UsagePage_GenericDesktop Usage_GD_Keypad CollectionApplication( ReportId(REPORT_ID_BUTTONS) /* Retain original ID on byte 0 */ ReportCount(1) ReportSize(REPORT_SIZE_PAD) UsagePage_Digitizers Usage_Dig_TabletFunctionKeys CollectionPhysical( /* Byte 1: Dial state */ UsagePage_GenericDesktop Usage_GD_Dial LogicalMinimum_i8(-1) LogicalMaximum_i8(1) ReportCount(1) ReportSize(REPORT_SIZE_PAD) Input(Var|Rel) /* Byte 2: Button state */ UsagePage_Button ReportSize(1) ReportCount(PAD_BUTTON_COUNT) UsageMinimum_i8(0x01) UsageMaximum_i8(PAD_BUTTON_COUNT) /* Number of buttons */ LogicalMinimum_i8(0x0) LogicalMaximum_i8(0x1) Input(Var|Abs) /* Byte 3: Exists to be tablet pad */ UsagePage_Digitizers Usage_Dig_BarrelSwitch ReportCount(1) ReportSize(1) Input(Var|Abs) ReportCount(7) /* Padding, to fill full report space */ Input(Const) /* Byte 4/5: Exists to be a tablet pad */ UsagePage_GenericDesktop Usage_GD_X Usage_GD_Y ReportCount(2) ReportSize(8) Input(Var|Abs) /* Bytes 6/7: Padding, to match original length */ ReportCount(2) ReportSize(8) Input(Const) ) FixedSizeVendorReport(RDESC_SIZE_PAD) ) }; SEC(HID_BPF_RDESC_FIXUP) int BPF_PROG(xppen_deco02_rdesc_fixup, struct hid_bpf_ctx *hctx) { __u8 *data = hid_bpf_get_data(hctx, 0, HID_MAX_DESCRIPTOR_SIZE); if (!data) return 0; /* EPERM Check */ if (hctx->size == RDESC_SIZE_PAD) { __builtin_memcpy(data, fixed_rdesc_pad, sizeof(fixed_rdesc_pad)); return sizeof(fixed_rdesc_pad); } return 0; } SEC(HID_BPF_DEVICE_EVENT) int BPF_PROG(xppen_deco02_device_event, struct hid_bpf_ctx *hctx) { __u8 *data = hid_bpf_get_data(hctx, 0, REPORT_SIZE_PAD); if (!data || data[0] != REPORT_ID_BUTTONS) return 0; /* EPERM or wrong report */ __u8 dial_code = 0; __u8 button_mask = 0; size_t d; /* Start from 2; 0 is report ID, 1 is modifier keys, replaced by dial */ for (d = 2; d < 8; d++) { switch (data[d]) { case 0x2e: dial_code = 1; break; case 0x2d: dial_code = -1; break; /* below are buttons, top to bottom */ case 0x05: button_mask |= BIT(0); break; case 0x2c: button_mask |= BIT(1); break; case 0x08: button_mask |= BIT(2); break; case 0x0c: button_mask |= BIT(3); break; case 0x1d: button_mask |= BIT(4); break; case 0x16: button_mask |= BIT(05); break; default: break; } } __u8 report[8] = { REPORT_ID_BUTTONS, dial_code, button_mask, 0x00 }; __builtin_memcpy(data, report, sizeof(report)); return 0; } HID_BPF_OPS(xppen_deco02) = { .hid_rdesc_fixup = (void *)xppen_deco02_rdesc_fixup, .hid_device_event = (void *)xppen_deco02_device_event, }; SEC("syscall") int probe(struct hid_bpf_probe_args *ctx) { ctx->retval = ctx->rdesc_size != RDESC_SIZE_PAD ? -EINVAL : 0; return 0; } char _license[] SEC("license") = "GPL";
