| // 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 <bpf/bpf_tracing.h> |
| |
| #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"; |
