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1// SPDX-License-Identifier: GPL-2.0-only2/* Copyright (c) 2024 José Expósito3 */4 5#include "vmlinux.h"6#include "hid_bpf.h"7#include "hid_bpf_helpers.h"8#include <bpf/bpf_tracing.h>9 10#define VID_UGEE 0x28BD11#define PID_DECO_MINI_4 0x092912#define RDESC_SIZE_PAD 17713#define RDESC_SIZE_PEN 10914#define PAD_REPORT_ID 0x0615 16/*17 * XP-Pen devices return a descriptor with the values the driver should use when18 * one of its interfaces is queried. For this device the descriptor is:19 *20 * 0E 03 60 4F 88 3B 06 00 FF 1F D8 1321 * ----- ----- ----- -----22 * | | | |23 * | | | `- Resolution: 5080 (13d8)24 * | | `- Maximum pressure: 8191 (1FFF)25 * | `- Logical maximum Y: 15240 (3B88)26 * `- Logical maximum X: 20320 (4F60)27 *28 * The physical maximum is calculated as (logical_max * 1000) / resolution.29 */30#define LOGICAL_MAX_X 0x60, 0x4F31#define LOGICAL_MAX_Y 0x88, 0x3B32#define PHYSICAL_MAX_X 0xA0, 0x0F33#define PHYSICAL_MAX_Y 0xB8, 0x0B34#define PRESSURE_MAX 0xFF, 0x1F35 36HID_BPF_CONFIG(37 HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_UGEE, PID_DECO_MINI_4)38);39 40/*41 * The tablet send these values when the pad buttons are pressed individually:42 *43 * Buttons released: 06 00 00 00 00 00 00 0044 * Button 1: 06 00 05 00 00 00 00 00 -> b45 * Button 2: 06 00 08 00 00 00 00 00 -> e46 * Button 3: 06 04 00 00 00 00 00 00 -> LAlt47 * Button 4: 06 00 2c 00 00 00 00 00 -> Space48 * Button 5: 06 01 16 00 00 00 00 00 -> LControl + s49 * Button 6: 06 01 1d 00 00 00 00 00 -> LControl + z50 *51 * When multiple buttons are pressed at the same time, the values used to52 * identify the buttons are identical, but they appear in different bytes of the53 * record. For example, when button 2 (0x08) and button 1 (0x05) are pressed,54 * this is the report:55 *56 * Buttons 2 and 1: 06 00 08 05 00 00 00 00 -> e + b57 *58 * Buttons 1, 2, 4, 5 and 6 can be matched by finding their values in the59 * report.60 *61 * Button 3 is pressed when the 3rd bit is 1. For example, pressing buttons 362 * and 5 generates this report:63 *64 * Buttons 3 and 5: 06 05 16 00 00 00 00 00 -> LControl + LAlt + s65 * -- --66 * | |67 * | `- Button 5 (0x16)68 * `- 0x05 = 0101. Button 3 is pressed69 * ^70 *71 * pad_buttons contains a list of buttons that can be matched in72 * HID_BPF_DEVICE_EVENT. Button 3 as it has a dedicated bit.73 */74static const __u8 pad_buttons[] = { 0x05, 0x08, 0x00, 0x2C, 0x16, 0x1D };75 76static const __u8 fixed_pad_rdesc[] = {77 0x05, 0x01, /* Usage Page (Desktop), */78 0x09, 0x07, /* Usage (Keypad), */79 0xA1, 0x01, /* Collection (Application), */80 0x85, 0x06, /* Report ID (6), */81 0x05, 0x0D, /* Usage Page (Digitizer), */82 0x09, 0x39, /* Usage (Tablet Function Keys), */83 0xA0, /* Collection (Physical), */84 0x05, 0x09, /* Usage Page (Button), */85 0x75, 0x01, /* Report Size (1), */86 0x95, 0x06, /* Report Count (6), */87 0x19, 0x01, /* Usage Minimum (01h), */88 0x29, 0x06, /* Usage Maximum (06h), */89 0x14, /* Logical Minimum (0), */90 0x25, 0x01, /* Logical Maximum (1), */91 0x81, 0x02, /* Input (Variable), */92 0x95, 0x32, /* Report Count (50), */93 0x81, 0x01, /* Input (Constant), */94 0xC0, /* End Collection, */95 0xC0 /* End Collection */96};97 98static const __u8 fixed_pen_rdesc[] = {99 0x05, 0x0d, /* Usage Page (Digitizers), */100 0x09, 0x01, /* Usage (Digitizer), */101 0xa1, 0x01, /* Collection (Application), */102 0x85, 0x07, /* Report ID (7), */103 0x09, 0x20, /* Usage (Stylus), */104 0xa1, 0x00, /* Collection (Physical), */105 0x09, 0x42, /* Usage (Tip Switch), */106 0x09, 0x44, /* Usage (Barrel Switch), */107 0x09, 0x46, /* Usage (Tablet Pick), */108 0x75, 0x01, /* Report Size (1), */109 0x95, 0x03, /* Report Count (3), */110 0x14, /* Logical Minimum (0), */111 0x25, 0x01, /* Logical Maximum (1), */112 0x81, 0x02, /* Input (Variable), */113 0x95, 0x02, /* Report Count (2), */114 0x81, 0x03, /* Input (Constant, Variable), */115 0x09, 0x32, /* Usage (In Range), */116 0x95, 0x01, /* Report Count (1), */117 0x81, 0x02, /* Input (Variable), */118 0x95, 0x02, /* Report Count (2), */119 0x81, 0x03, /* Input (Constant, Variable), */120 0x75, 0x10, /* Report Size (16), */121 0x95, 0x01, /* Report Count (1), */122 0x35, 0x00, /* Physical Minimum (0), */123 0xa4, /* Push, */124 0x05, 0x01, /* Usage Page (Desktop), */125 0x09, 0x30, /* Usage (X), */126 0x65, 0x13, /* Unit (Inch), */127 0x55, 0x0d, /* Unit Exponent (-3), */128 0x26, LOGICAL_MAX_X, /* Logical Maximum, */129 0x46, PHYSICAL_MAX_X, /* Physical Maximum, */130 0x81, 0x02, /* Input (Variable), */131 0x09, 0x31, /* Usage (Y), */132 0x26, LOGICAL_MAX_Y, /* Logical Maximum, */133 0x46, PHYSICAL_MAX_Y, /* Physical Maximum, */134 0x81, 0x02, /* Input (Variable), */135 0xb4, /* Pop, */136 0x09, 0x30, /* Usage (Tip Pressure), */137 0x45, 0x00, /* Physical Maximum (0), */138 0x26, PRESSURE_MAX, /* Logical Maximum, */139 0x75, 0x0D, /* Report Size (13), */140 0x95, 0x01, /* Report Count (1), */141 0x81, 0x02, /* Input (Variable), */142 0x75, 0x01, /* Report Size (1), */143 0x95, 0x13, /* Report Count (19), */144 0x81, 0x01, /* Input (Constant), */145 0xc0, /* End Collection, */146 0xc0, /* End Collection */147};148 149static const size_t fixed_pad_rdesc_size = sizeof(fixed_pad_rdesc);150static const size_t fixed_pen_rdesc_size = sizeof(fixed_pen_rdesc);151 152SEC(HID_BPF_RDESC_FIXUP)153int BPF_PROG(hid_rdesc_fixup_xppen_deco_mini_4, struct hid_bpf_ctx *hctx)154{155 __u8 *data = hid_bpf_get_data(hctx, 0, HID_MAX_DESCRIPTOR_SIZE);156 157 if (!data)158 return 0; /* EPERM check */159 160 if (hctx->size == RDESC_SIZE_PAD) {161 __builtin_memcpy(data, fixed_pad_rdesc, fixed_pad_rdesc_size);162 return fixed_pad_rdesc_size;163 } else if (hctx->size == RDESC_SIZE_PEN) {164 __builtin_memcpy(data, fixed_pen_rdesc, fixed_pen_rdesc_size);165 return fixed_pen_rdesc_size;166 }167 168 return 0;169}170 171SEC(HID_BPF_DEVICE_EVENT)172int BPF_PROG(hid_device_event_xppen_deco_mini_4, struct hid_bpf_ctx *hctx)173{174 __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 8 /* size */);175 __u8 button_mask = 0;176 int d, b;177 178 if (!data)179 return 0; /* EPERM check */180 181 if (data[0] != PAD_REPORT_ID)182 return 0;183 184 /* data[1] stores the status of BTN_2 in the 3rd bit*/185 if (data[1] & BIT(2))186 button_mask |= BIT(2);187 188 /* The rest of the descriptor stores the buttons as in pad_buttons */189 for (d = 2; d < 8; d++) {190 for (b = 0; b < sizeof(pad_buttons); b++) {191 if (data[d] != 0 && data[d] == pad_buttons[b])192 button_mask |= BIT(b);193 }194 }195 196 __u8 report[8] = {PAD_REPORT_ID, button_mask, 0x00};197 198 __builtin_memcpy(data, report, sizeof(report));199 200 return 0;201}202 203HID_BPF_OPS(deco_mini_4) = {204 .hid_device_event = (void *)hid_device_event_xppen_deco_mini_4,205 .hid_rdesc_fixup = (void *)hid_rdesc_fixup_xppen_deco_mini_4,206};207 208SEC("syscall")209int probe(struct hid_bpf_probe_args *ctx)210{211 /*212 * The device has 2 modes: The compatibility mode, enabled by default,213 * and the raw mode, that can be activated by sending a buffer of magic214 * data to a certain USB endpoint.215 *216 * Depending on the mode, different interfaces of the device are used:217 * - First interface: Pad in compatibility mode218 * - Second interface: Pen in compatibility mode219 * - Third interface: Only used in raw mode220 *221 * We'll use the device in compatibility mode.222 */223 ctx->retval = ctx->rdesc_size != RDESC_SIZE_PAD &&224 ctx->rdesc_size != RDESC_SIZE_PEN;225 if (ctx->retval)226 ctx->retval = -EINVAL;227 228 return 0;229}230 231char _license[] SEC("license") = "GPL";232