// SPDX-License-Identifier: GPL-2.0-only /* Copyright (c) 2024 José Expósito */ #include "vmlinux.h" #include "hid_bpf.h" #include "hid_bpf_helpers.h" #include #define VID_UGEE 0x28BD #define PID_DECO_MINI_4 0x0929 #define RDESC_SIZE_PAD 177 #define RDESC_SIZE_PEN 109 #define PAD_REPORT_ID 0x06 /* * XP-Pen devices return a descriptor with the values the driver should use when * one of its interfaces is queried. For this device the descriptor is: * * 0E 03 60 4F 88 3B 06 00 FF 1F D8 13 * ----- ----- ----- ----- * | | | | * | | | `- Resolution: 5080 (13d8) * | | `- Maximum pressure: 8191 (1FFF) * | `- Logical maximum Y: 15240 (3B88) * `- Logical maximum X: 20320 (4F60) * * The physical maximum is calculated as (logical_max * 1000) / resolution. */ #define LOGICAL_MAX_X 0x60, 0x4F #define LOGICAL_MAX_Y 0x88, 0x3B #define PHYSICAL_MAX_X 0xA0, 0x0F #define PHYSICAL_MAX_Y 0xB8, 0x0B #define PRESSURE_MAX 0xFF, 0x1F HID_BPF_CONFIG( HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_UGEE, PID_DECO_MINI_4) ); /* * The tablet send these values when the pad buttons are pressed individually: * * Buttons released: 06 00 00 00 00 00 00 00 * Button 1: 06 00 05 00 00 00 00 00 -> b * Button 2: 06 00 08 00 00 00 00 00 -> e * Button 3: 06 04 00 00 00 00 00 00 -> LAlt * Button 4: 06 00 2c 00 00 00 00 00 -> Space * Button 5: 06 01 16 00 00 00 00 00 -> LControl + s * Button 6: 06 01 1d 00 00 00 00 00 -> LControl + z * * 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. */ static const __u8 pad_buttons[] = { 0x05, 0x08, 0x00, 0x2C, 0x16, 0x1D }; static const __u8 fixed_pad_rdesc[] = { 0x05, 0x01, /* Usage Page (Desktop), */ 0x09, 0x07, /* Usage (Keypad), */ 0xA1, 0x01, /* Collection (Application), */ 0x85, 0x06, /* Report ID (6), */ 0x05, 0x0D, /* Usage Page (Digitizer), */ 0x09, 0x39, /* Usage (Tablet Function Keys), */ 0xA0, /* Collection (Physical), */ 0x05, 0x09, /* Usage Page (Button), */ 0x75, 0x01, /* Report Size (1), */ 0x95, 0x06, /* Report Count (6), */ 0x19, 0x01, /* Usage Minimum (01h), */ 0x29, 0x06, /* Usage Maximum (06h), */ 0x14, /* Logical Minimum (0), */ 0x25, 0x01, /* Logical Maximum (1), */ 0x81, 0x02, /* Input (Variable), */ 0x95, 0x32, /* Report Count (50), */ 0x81, 0x01, /* Input (Constant), */ 0xC0, /* End Collection, */ 0xC0 /* End Collection */ }; static const __u8 fixed_pen_rdesc[] = { 0x05, 0x0d, /* Usage Page (Digitizers), */ 0x09, 0x01, /* Usage (Digitizer), */ 0xa1, 0x01, /* Collection (Application), */ 0x85, 0x07, /* Report ID (7), */ 0x09, 0x20, /* Usage (Stylus), */ 0xa1, 0x00, /* Collection (Physical), */ 0x09, 0x42, /* Usage (Tip Switch), */ 0x09, 0x44, /* Usage (Barrel Switch), */ 0x09, 0x46, /* Usage (Tablet Pick), */ 0x75, 0x01, /* Report Size (1), */ 0x95, 0x03, /* Report Count (3), */ 0x14, /* Logical Minimum (0), */ 0x25, 0x01, /* Logical Maximum (1), */ 0x81, 0x02, /* Input (Variable), */ 0x95, 0x02, /* Report Count (2), */ 0x81, 0x03, /* Input (Constant, Variable), */ 0x09, 0x32, /* Usage (In Range), */ 0x95, 0x01, /* Report Count (1), */ 0x81, 0x02, /* Input (Variable), */ 0x95, 0x02, /* Report Count (2), */ 0x81, 0x03, /* Input (Constant, Variable), */ 0x75, 0x10, /* Report Size (16), */ 0x95, 0x01, /* Report Count (1), */ 0x35, 0x00, /* Physical Minimum (0), */ 0xa4, /* Push, */ 0x05, 0x01, /* Usage Page (Desktop), */ 0x09, 0x30, /* Usage (X), */ 0x65, 0x13, /* Unit (Inch), */ 0x55, 0x0d, /* Unit Exponent (-3), */ 0x26, LOGICAL_MAX_X, /* Logical Maximum, */ 0x46, PHYSICAL_MAX_X, /* Physical Maximum, */ 0x81, 0x02, /* Input (Variable), */ 0x09, 0x31, /* Usage (Y), */ 0x26, LOGICAL_MAX_Y, /* Logical Maximum, */ 0x46, PHYSICAL_MAX_Y, /* Physical Maximum, */ 0x81, 0x02, /* Input (Variable), */ 0xb4, /* Pop, */ 0x09, 0x30, /* Usage (Tip Pressure), */ 0x45, 0x00, /* Physical Maximum (0), */ 0x26, PRESSURE_MAX, /* Logical Maximum, */ 0x75, 0x0D, /* Report Size (13), */ 0x95, 0x01, /* Report Count (1), */ 0x81, 0x02, /* Input (Variable), */ 0x75, 0x01, /* Report Size (1), */ 0x95, 0x13, /* Report Count (19), */ 0x81, 0x01, /* Input (Constant), */ 0xc0, /* End Collection, */ 0xc0, /* End Collection */ }; static const size_t fixed_pad_rdesc_size = sizeof(fixed_pad_rdesc); static const size_t fixed_pen_rdesc_size = sizeof(fixed_pen_rdesc); SEC(HID_BPF_RDESC_FIXUP) int BPF_PROG(hid_rdesc_fixup_xppen_deco_mini_4, 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_pad_rdesc, fixed_pad_rdesc_size); return fixed_pad_rdesc_size; } else if (hctx->size == RDESC_SIZE_PEN) { __builtin_memcpy(data, fixed_pen_rdesc, fixed_pen_rdesc_size); return fixed_pen_rdesc_size; } return 0; } SEC(HID_BPF_DEVICE_EVENT) int BPF_PROG(hid_device_event_xppen_deco_mini_4, struct hid_bpf_ctx *hctx) { __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 8 /* size */); __u8 button_mask = 0; int d, b; if (!data) return 0; /* EPERM check */ if (data[0] != PAD_REPORT_ID) return 0; /* 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(deco_mini_4) = { .hid_device_event = (void *)hid_device_event_xppen_deco_mini_4, .hid_rdesc_fixup = (void *)hid_rdesc_fixup_xppen_deco_mini_4, }; SEC("syscall") int probe(struct hid_bpf_probe_args *ctx) { /* * The device has 2 modes: The compatibility mode, enabled by default, * and the raw mode, that can be activated by sending a buffer of magic * data to a certain USB endpoint. * * Depending on the mode, different interfaces of the device are used: * - First interface: Pad in compatibility mode * - Second interface: Pen in compatibility mode * - Third interface: Only used in raw mode * * We'll use the device in compatibility mode. */ ctx->retval = ctx->rdesc_size != RDESC_SIZE_PAD && ctx->rdesc_size != RDESC_SIZE_PEN; if (ctx->retval) ctx->retval = -EINVAL; return 0; } char _license[] SEC("license") = "GPL";