CoCalc -- Huion__KeydialK20-Bluetooth.bpf.c

GitHub Repository: torvalds/linux
Path: blob/master/drivers/hid/bpf/progs/Huion__KeydialK20-Bluetooth.bpf.c
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// SPDX-License-Identifier: GPL-2.0-only
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/* Copyright (c) 2024 Red Hat, Inc
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 */
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#include "vmlinux.h"
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#include "hid_bpf.h"
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#include "hid_bpf_helpers.h"
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#include "hid_report_helpers.h"
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#include <bpf/bpf_tracing.h>
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#define VID_HUION 0x256C
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#define PID_KEYDIAL_K20_BLUETOOTH 0x8251
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HID_BPF_CONFIG(
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	HID_DEVICE(BUS_BLUETOOTH, HID_GROUP_GENERIC, VID_HUION, PID_KEYDIAL_K20_BLUETOOTH),
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);
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/* This is the same device as in 0010-Huion__KeydialK20 but connected via Bluetooth.
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 * It does not need (to support?) switching to a vendor mode so we just modify the
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 * existing mode.
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 *
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 * By default it exports two hidraw nodes, only the second one sends events.
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 *
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 * This is the first hidraw node which we disable:
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 *
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 * # Keydial mini-050
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 * # Report descriptor length: 114 bytes
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 * #   Bytes                          // Field Name                              Offset
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 * # ----------------------------------------------------------------------------------
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 * # 🮥 0x05, 0x01,                    // Usage Page (Generic Desktop)              0
31
 * # 🭬 0x09, 0x0e,                    // Usage (System Multi-Axis Controller)      2
32
 * #   0xa1, 0x01,                    // Collection (Application)                  4
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 * # ┅ 0x85, 0x03,                    //   Report ID (3)                           6
34
 * # 🮥 0x05, 0x0d,                    //   Usage Page (Digitizers)                 8
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 * #   0x75, 0x08,                    //   Report Size (8)                         10
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 * #   0x95, 0x01,                    //   Report Count (1)                        12
37
 * # ┇ 0x81, 0x01,                    //   Input (Cnst,Arr,Abs)                    14
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 * # 🭬 0x09, 0x21,                    //   Usage (Puck)                            16
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 * #   0xa1, 0x02,                    //   Collection (Logical)                    18
40
 * #   0x15, 0x00,                    //     Logical Minimum (0)                   20
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 * #   0x25, 0x01,                    //     Logical Maximum (1)                   22
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 * #   0x75, 0x01,                    //     Report Size (1)                       24
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 * #   0x95, 0x01,                    //     Report Count (1)                      26
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 * #   0xa1, 0x00,                    //     Collection (Physical)                 28
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 * # 🮥 0x05, 0x09,                    //       Usage Page (Button)                 30
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 * # 🭬 0x09, 0x01,                    //       Usage (Button 1)                    32
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 * # ┇ 0x81, 0x02,                    //       Input (Data,Var,Abs)                34
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 * # 🮥 0x05, 0x0d,                    //       Usage Page (Digitizers)             36
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 * # 🭬 0x09, 0x33,                    //       Usage (Touch)                       38
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 * # ┇ 0x81, 0x02,                    //       Input (Data,Var,Abs)                40
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 * #   0x95, 0x06,                    //       Report Count (6)                    42
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 * # ┇ 0x81, 0x03,                    //       Input (Cnst,Var,Abs)                44
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 * #   0xa1, 0x02,                    //       Collection (Logical)                46
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 * # 🮥 0x05, 0x01,                    //         Usage Page (Generic Desktop)      48
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 * # 🭬 0x09, 0x37,                    //         Usage (Dial)                      50
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 * #   0x16, 0x00, 0x80,              //         Logical Minimum (32768)           52
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 * #   0x26, 0xff, 0x7f,              //         Logical Maximum (32767)           55
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 * #   0x75, 0x10,                    //         Report Size (16)                  58
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 * #   0x95, 0x01,                    //         Report Count (1)                  60
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 * # ┇ 0x81, 0x06,                    //         Input (Data,Var,Rel)              62
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 * #   0x35, 0x00,                    //         Physical Minimum (0)              64
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 * #   0x46, 0x10, 0x0e,              //         Physical Maximum (3600)           66
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 * #   0x15, 0x00,                    //         Logical Minimum (0)               69
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 * #   0x26, 0x10, 0x0e,              //         Logical Maximum (3600)            71
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 * # 🭬 0x09, 0x48,                    //         Usage (Resolution Multiplier)     74
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 * # ║ 0xb1, 0x02,                    //         Feature (Data,Var,Abs)            76
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 * #   0x45, 0x00,                    //         Physical Maximum (0)              78
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 * #   0xc0,                          //       End Collection                      80
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 * #   0x75, 0x08,                    //       Report Size (8)                     81
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 * #   0x95, 0x01,                    //       Report Count (1)                    83
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 * # ┇ 0x81, 0x01,                    //       Input (Cnst,Arr,Abs)                85
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 * #   0x75, 0x08,                    //       Report Size (8)                     87
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 * #   0x95, 0x01,                    //       Report Count (1)                    89
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 * # ┇ 0x81, 0x01,                    //       Input (Cnst,Arr,Abs)                91
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 * #   0x75, 0x08,                    //       Report Size (8)                     93
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 * #   0x95, 0x01,                    //       Report Count (1)                    95
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 * # ┇ 0x81, 0x01,                    //       Input (Cnst,Arr,Abs)                97
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 * #   0x75, 0x08,                    //       Report Size (8)                     99
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 * #   0x95, 0x01,                    //       Report Count (1)                    101
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 * # ┇ 0x81, 0x01,                    //       Input (Cnst,Arr,Abs)                103
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 * #   0x75, 0x08,                    //       Report Size (8)                     105
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 * #   0x95, 0x01,                    //       Report Count (1)                    107
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 * # ┇ 0x81, 0x01,                    //       Input (Cnst,Arr,Abs)                109
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 * #   0xc0,                          //     End Collection                        111
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 * #   0xc0,                          //   End Collection                          112
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 * #   0xc0,                          // End Collection                            113
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 * R: 114 05 01 09 0e a1 01 85 03 05 0d 75 08 95 01 81 01 09 21 a1 02 15 00 25 01 75 01 95 01 a1 00 05 09 09 01 81 02 05 0d 09 33 81 02 95 06 81 03 a1 02 05 01 09 37 16 00 80 26 ff 7f 75 10 95 01 81 06 35 00 46 10 0e 15 00 26 10 0e 09 48 b1 02 45 00 c0 75 08 95 01 81 01 75 08 95 01 81 01 75 08 95 01 81 01 75 08 95 01 81 01 75 08 95 01 81 01 c0 c0 c0
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 * N: Keydial mini-050
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 * I: 5 256c 8251
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 *
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 * The second hidraw node is what sends events:
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 *
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 * # Keydial mini-050
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 * # Report descriptor length: 160 bytes
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 * #   Bytes                          // Field Name                              Offset
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 * # ----------------------------------------------------------------------------------
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 * # 🮥 0x05, 0x01,                    // Usage Page (Generic Desktop)              0
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 * # 🭬 0x09, 0x06,                    // Usage (Keyboard)                          2
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 * #   0xa1, 0x01,                    // Collection (Application)                  4
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 * # ┅ 0x85, 0x01,                    //   Report ID (1)                           6
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 * # 🮥 0x05, 0x07,                    //   Usage Page (Keyboard/Keypad)            8
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 * # 🭬 0x19, 0xe0,                    //   Usage Minimum (224)                     10
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 * # 🭬 0x29, 0xe7,                    //   Usage Maximum (231)                     12
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 * #   0x15, 0x00,                    //   Logical Minimum (0)                     14
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 * #   0x25, 0x01,                    //   Logical Maximum (1)                     16
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 * #   0x75, 0x01,                    //   Report Size (1)                         18
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 * #   0x95, 0x08,                    //   Report Count (8)                        20
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 * # ┇ 0x81, 0x02,                    //   Input (Data,Var,Abs)                    22
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 * #   0x95, 0x01,                    //   Report Count (1)                        24
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 * #   0x75, 0x08,                    //   Report Size (8)                         26
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 * # ┇ 0x81, 0x01,                    //   Input (Cnst,Arr,Abs)                    28
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 * #   0x95, 0x05,                    //   Report Count (5)                        30
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 * #   0x75, 0x01,                    //   Report Size (1)                         32
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 * # 🮥 0x05, 0x08,                    //   Usage Page (LED)                        34
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 * # 🭬 0x19, 0x01,                    //   Usage Minimum (1)                       36
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 * # 🭬 0x29, 0x05,                    //   Usage Maximum (5)                       38
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 * # ┊ 0x91, 0x02,                    //   Output (Data,Var,Abs)                   40
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 * #   0x95, 0x01,                    //   Report Count (1)                        42
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 * #   0x75, 0x03,                    //   Report Size (3)                         44
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 * # ┊ 0x91, 0x01,                    //   Output (Cnst,Arr,Abs)                   46
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 * #   0x95, 0x06,                    //   Report Count (6)                        48
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 * #   0x75, 0x08,                    //   Report Size (8)                         50
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 * #   0x15, 0x00,                    //   Logical Minimum (0)                     52
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 * #   0x25, 0xf1,                    //   Logical Maximum (241)                   54
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 * # 🮥 0x05, 0x07,                    //   Usage Page (Keyboard/Keypad)            56
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 * # 🭬 0x19, 0x00,                    //   Usage Minimum (0)                       58
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 * # 🭬 0x29, 0xf1,                    //   Usage Maximum (241)                     60
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 * # ┇ 0x81, 0x00,                    //   Input (Data,Arr,Abs)                    62
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 * #   0xc0,                          // End Collection                            64
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 * # 🮥 0x05, 0x0c,                    // Usage Page (Consumer)                     65
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 * # 🭬 0x09, 0x01,                    // Usage (Consumer Control)                  67
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 * #   0xa1, 0x01,                    // Collection (Application)                  69
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 * # ┅ 0x85, 0x02,                    //   Report ID (2)                           71
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 * # 🮥 0x05, 0x0c,                    //   Usage Page (Consumer)                   73
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 * # 🭬 0x19, 0x00,                    //   Usage Minimum (0)                       75
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 * # 🭬 0x2a, 0x80, 0x03,              //   Usage Maximum (896)                     77
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 * #   0x15, 0x00,                    //   Logical Minimum (0)                     80
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 * #   0x26, 0x80, 0x03,              //   Logical Maximum (896)                   82
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 * #   0x75, 0x10,                    //   Report Size (16)                        85
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 * #   0x95, 0x01,                    //   Report Count (1)                        87
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 * # ┇ 0x81, 0x00,                    //   Input (Data,Arr,Abs)                    89
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 * #   0xc0,                          // End Collection                            91
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 * # 🮥 0x05, 0x01,                    // Usage Page (Generic Desktop)              92
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 * # 🭬 0x09, 0x02,                    // Usage (Mouse)                             94
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 * #   0xa1, 0x01,                    // Collection (Application)                  96
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 * # 🭬 0x09, 0x01,                    //   Usage (Pointer)                         98
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 * # ┅ 0x85, 0x05,                    //   Report ID (5)                           100
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 * #   0xa1, 0x00,                    //   Collection (Physical)                   102
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 * # 🮥 0x05, 0x09,                    //     Usage Page (Button)                   104
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 * # 🭬 0x19, 0x01,                    //     Usage Minimum (1)                     106
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 * # 🭬 0x29, 0x05,                    //     Usage Maximum (5)                     108
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 * #   0x15, 0x00,                    //     Logical Minimum (0)                   110
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 * #   0x25, 0x01,                    //     Logical Maximum (1)                   112
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 * #   0x95, 0x05,                    //     Report Count (5)                      114
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 * #   0x75, 0x01,                    //     Report Size (1)                       116
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 * # ┇ 0x81, 0x02,                    //     Input (Data,Var,Abs)                  118
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 * #   0x95, 0x01,                    //     Report Count (1)                      120
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 * #   0x75, 0x03,                    //     Report Size (3)                       122
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 * # ┇ 0x81, 0x01,                    //     Input (Cnst,Arr,Abs)                  124
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 * # 🮥 0x05, 0x01,                    //     Usage Page (Generic Desktop)          126
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 * # 🭬 0x09, 0x30,                    //     Usage (X)                             128
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 * # 🭬 0x09, 0x31,                    //     Usage (Y)                             130
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 * #   0x16, 0x01, 0x80,              //     Logical Minimum (32769)               132
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 * #   0x26, 0xff, 0x7f,              //     Logical Maximum (32767)               135
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 * #   0x75, 0x10,                    //     Report Size (16)                      138
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 * #   0x95, 0x02,                    //     Report Count (2)                      140
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 * # ┇ 0x81, 0x06,                    //     Input (Data,Var,Rel)                  142
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 * # 🮥 0x05, 0x01,                    //     Usage Page (Generic Desktop)          144
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 * # 🭬 0x09, 0x38,                    //     Usage (Wheel)                         146
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 * #   0x15, 0x81,                    //     Logical Minimum (129)                 148
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 * #   0x25, 0x7f,                    //     Logical Maximum (127)                 150
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 * #   0x95, 0x01,                    //     Report Count (1)                      152
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 * #   0x75, 0x08,                    //     Report Size (8)                       154
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 * # ┇ 0x81, 0x06,                    //     Input (Data,Var,Rel)                  156
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 * #   0xc0,                          //   End Collection                          158
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 * #   0xc0,                          // End Collection                            159
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 * R: 160 05 01 09 06 a1 01 85 01 05 07 19 e0 29 e7 15 00 25 01 75 01 95 08 81 02 95 01 75 08 81 01 95 05 75 01 05 08 19 01 29 05 91 02 95 01 75 03 91 01 95 06 75 08 15 00 25 f1 05 07 19 00 29 f1 81 00 c0 05 0c 09 01 a1 01 85 02 05 0c 19 00 2a 80 03 15 00 26 80 03 75 10 95 01 81 00 c0 05 01 09 02 a1 01 09 01 85 05 a1 00 05 09 19 01 29 05 15 00 25 01 95 05 75 01 81 02 95 01 75 03 81 01 05 01 09 30 09 31 16 01 80 26 ff 7f 75 10 95 02 81 06 05 01 09 38 15 81 25 7f 95 01 75 08 81 06 c0 c0
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 * N: Keydial mini-050
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 * I: 5 256c 8251
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 * # Report descriptor:
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 * # ------- Input Report -------
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 * # ░ Report ID: 1
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 * # ░  | Report size: 72 bits
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 * # ░ Bit:    8       Usage: 0007/00e0: Keyboard/Keypad / Keyboard LeftControl      Logical Range:     0..=1
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 * # ░ Bit:    9       Usage: 0007/00e1: Keyboard/Keypad / Keyboard LeftShift        Logical Range:     0..=1
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 * # ░ Bit:   10       Usage: 0007/00e2: Keyboard/Keypad / Keyboard LeftAlt          Logical Range:     0..=1
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 * # ░ Bit:   11       Usage: 0007/00e3: Keyboard/Keypad / Keyboard Left GUI         Logical Range:     0..=1
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 * # ░ Bit:   12       Usage: 0007/00e4: Keyboard/Keypad / Keyboard RightControl     Logical Range:     0..=1
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 * # ░ Bit:   13       Usage: 0007/00e5: Keyboard/Keypad / Keyboard RightShift       Logical Range:     0..=1
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 * # ░ Bit:   14       Usage: 0007/00e6: Keyboard/Keypad / Keyboard RightAlt         Logical Range:     0..=1
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 * # ░ Bit:   15       Usage: 0007/00e7: Keyboard/Keypad / Keyboard Right GUI        Logical Range:     0..=1
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 * # ░ Bits:  16..=23  ######### Padding
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 * # ░ Bits:  24..=71  Usages:                                                       Logical Range:     0..=241
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 * # ░                 0007/0000: <unknown>
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 * # ░                 0007/0001: Keyboard/Keypad / ErrorRollOver
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 * # ░                 0007/0002: Keyboard/Keypad / POSTFail
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 * # ░                 0007/0003: Keyboard/Keypad / ErrorUndefined
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 * # ░                 0007/0004: Keyboard/Keypad / Keyboard A
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 * # ░                 ... use --full to see all usages
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 * # ------- Input Report -------
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 * # ▒ Report ID: 2
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 * # ▒  | Report size: 24 bits
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 * # ▒ Bits:   8..=23  Usages:                                                Logical Range:     0..=896
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 * # ▒                 000c/0000: <unknown>
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 * # ▒                 000c/0001: Consumer / Consumer Control
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 * # ▒                 000c/0002: Consumer / Numeric Key Pad
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 * # ▒                 000c/0003: Consumer / Programmable Buttons
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 * # ▒                 000c/0004: Consumer / Microphone
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 * # ▒                 ... use --full to see all usages
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 * # ------- Input Report -------
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 * # ▞ Report ID: 5
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 * # ▞  | Report size: 56 bits
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 * # ▞ Bit:    8       Usage: 0009/0001: Button / Button 1                           Logical Range:     0..=1
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 * # ▞ Bit:    9       Usage: 0009/0002: Button / Button 2                           Logical Range:     0..=1
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 * # ▞ Bit:   10       Usage: 0009/0003: Button / Button 3                           Logical Range:     0..=1
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 * # ▞ Bit:   11       Usage: 0009/0004: Button / Button 4                           Logical Range:     0..=1
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 * # ▞ Bit:   12       Usage: 0009/0005: Button / Button 5                           Logical Range:     0..=1
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 * # ▞ Bits:  13..=15  ######### Padding
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 * # ▞ Bits:  16..=31  Usage: 0001/0030: Generic Desktop / X                         Logical Range: 32769..=32767
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 * # ▞ Bits:  32..=47  Usage: 0001/0031: Generic Desktop / Y                         Logical Range: 32769..=32767
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 * # ▞ Bits:  48..=55  Usage: 0001/0038: Generic Desktop / Wheel                     Logical Range:   129..=127
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 * # ------- Output Report -------
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 * # ░ Report ID: 1
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 * # ░  | Report size: 16 bits
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 * # ░ Bit:    8       Usage: 0008/0001: LED / Num Lock                              Logical Range:     0..=1
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 * # ░ Bit:    9       Usage: 0008/0002: LED / Caps Lock                             Logical Range:     0..=1
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 * # ░ Bit:   10       Usage: 0008/0003: LED / Scroll Lock                           Logical Range:     0..=1
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 * # ░ Bit:   11       Usage: 0008/0004: LED / Compose                               Logical Range:     0..=1
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 * # ░ Bit:   12       Usage: 0008/0005: LED / Kana                                  Logical Range:     0..=1
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 * # ░ Bits:  13..=15  ######### Padding
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 * ##############################################################################
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 * # Event nodes:
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 * # - /dev/input/event12: "Keydial mini-050 Keyboard"
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 * # - /dev/input/event14: "Keydial mini-050 Mouse"
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 * ##############################################################################
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 * # Recorded events below in format:
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 * # E: <seconds>.<microseconds> <length-in-bytes> [bytes ...]
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 * #
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 *
240
 * - Report ID 1 sends keyboard shortcuts when pressing the buttons, e.g.
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 *
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 * # ░  Report ID: 1 /
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 * # ░               Keyboard LeftControl:     0 |Keyboard LeftShift:     0 |Keyboard LeftAlt:     0 |Keyboard Left GUI:     0 |Keyboard RightControl:     0 |Keyboard RightShift:     0 |Keyboard RightAlt:     0 |Keyboard Right GUI:     0 |<8 bits padding> |0007/0000:     0| Keyboard K:    14| 0007/0000:     0| 0007/0000:     0| 0007/0000:     0| 0007/0000:     0
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 * E: 000000.000292 9 01 00 00 00 0e 00 00 00 00
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 *
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 * - Report ID 2 sends the button inside the wheel/dial thing
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 * # ▒  Report ID: 2 /
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 * # ▒               Play/Pause:   205
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 * E: 000134.347845 3 02 cd 00
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 * # ▒  Report ID: 2 /
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 * # ▒               000c/0000:     0
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 * E: 000134.444965 3 02 00 00
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 *
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 * - Report ID 5 sends the wheel relative events (always a double-event with the second as zero)
255
 * # ▞  Report ID: 5 /
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 * # ▞               Button 1:     0 |Button 2:     0 |Button 3:     0 |Button 4:     0 |Button 5:     0 |<3 bits padding> |X:     0 |Y:     0 |Wheel:   255
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 * E: 000064.859915 7 05 00 00 00 00 00 ff
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 * # ▞  Report ID: 5 /
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 * # ▞               Button 1:     0 |Button 2:     0 |Button 3:     0 |Button 4:     0 |Button 5:     0 |<3 bits padding> |X:     0 |Y:     0 |Wheel:     0
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 * E: 000064.882009 7 05 00 00 00 00 00 00
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 */
262

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#define BT_PAD_REPORT_DESCRIPTOR_LENGTH 160
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#define BT_PUCK_REPORT_DESCRIPTOR_LENGTH 114  // This one doesn't send events
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#define BT_PAD_KBD_REPORT_ID 1
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#define BT_PAD_CC_REPORT_ID 2
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#define BT_PAD_MOUSE_REPORT_ID 5
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#define BT_PAD_KBD_REPORT_LENGTH 9
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#define BT_PAD_CC_REPORT_LENGTH 3
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#define BT_PAD_MOUSE_REPORT_LENGTH 7
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#define OUR_REPORT_ID 11 /* "randomly" picked report ID for our reports */
272

273
__u32 last_button_state = 0;
274

275
static const __u8 disabled_rdesc_puck[] = {
276
	FixedSizeVendorReport(BT_PUCK_REPORT_DESCRIPTOR_LENGTH)
277
};
278

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static const __u8 fixed_rdesc_pad[] = {
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	UsagePage_GenericDesktop
281
	Usage_GD_Keypad
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	CollectionApplication(
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		// Byte 0
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		ReportId(OUR_REPORT_ID)
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		UsagePage_Digitizers
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		Usage_Dig_TabletFunctionKeys
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		CollectionPhysical(
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			// Byte 1 is a button so we look like a tablet
289
			Usage_Dig_BarrelSwitch	 // BTN_STYLUS, needed so we get to be a tablet pad
290
			ReportCount(1)
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			ReportSize(1)
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			Input(Var|Abs)
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			ReportCount(7) // Padding
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			Input(Const)
295
			// Bytes 2/3 - x/y just exist so we get to be a tablet pad
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			UsagePage_GenericDesktop
297
			Usage_GD_X
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			Usage_GD_Y
299
			LogicalMinimum_i8(0x0)
300
			LogicalMaximum_i8(0x1)
301
			ReportCount(2)
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			ReportSize(8)
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			Input(Var|Abs)
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			// Bytes 4-7 are the button state for 19 buttons + pad out to u32
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			// We send the first 10 buttons as buttons 1-10 which is BTN_0 -> BTN_9
306
			UsagePage_Button
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			UsageMinimum_i8(1)
308
			UsageMaximum_i8(10)
309
			LogicalMinimum_i8(0x0)
310
			LogicalMaximum_i8(0x1)
311
			ReportCount(10)
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			ReportSize(1)
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			Input(Var|Abs)
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			// We send the other 9 buttons as buttons 0x31 and above -> BTN_A - BTN_TL2
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			UsageMinimum_i8(0x31)
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			UsageMaximum_i8(0x3a)
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			ReportCount(9)
318
			ReportSize(1)
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			Input(Var|Abs)
320
			ReportCount(13)
321
			ReportSize(1)
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			Input(Const) // padding
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			// Byte 8 is the wheel
324
			UsagePage_GenericDesktop
325
			Usage_GD_Wheel
326
			LogicalMinimum_i8(-1)
327
			LogicalMaximum_i8(1)
328
			ReportCount(1)
329
			ReportSize(8)
330
			Input(Var|Rel)
331
		)
332
		// Make sure we match our original report length
333
		FixedSizeVendorReport(BT_PAD_KBD_REPORT_LENGTH)
334
	)
335
};
336

337
SEC(HID_BPF_RDESC_FIXUP)
338
int BPF_PROG(k20_bt_fix_rdesc, struct hid_bpf_ctx *hctx)
339
{
340
	__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, HID_MAX_DESCRIPTOR_SIZE /* size */);
341
	__s32 rdesc_size = hctx->size;
342

343
	if (!data)
344
		return 0; /* EPERM check */
345

346
	if (rdesc_size == BT_PAD_REPORT_DESCRIPTOR_LENGTH) {
347
		__builtin_memcpy(data, fixed_rdesc_pad, sizeof(fixed_rdesc_pad));
348
		return sizeof(fixed_rdesc_pad);
349
	}
350
	if (rdesc_size == BT_PUCK_REPORT_DESCRIPTOR_LENGTH) {
351
		// This hidraw node doesn't send anything and can be ignored
352
		__builtin_memcpy(data, disabled_rdesc_puck, sizeof(disabled_rdesc_puck));
353
		return sizeof(disabled_rdesc_puck);
354
	}
355

356
	return 0;
357
}
358

359
SEC(HID_BPF_DEVICE_EVENT)
360
int BPF_PROG(k20_bt_fix_events, struct hid_bpf_ctx *hctx)
361
{
362
	__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 12 /* size */);
363
	struct pad_report {
364
		__u8 report_id;
365
		__u8 btn_stylus:1;
366
		__u8 pad:7;
367
		__u8 x;
368
		__u8 y;
369
		__u32 buttons;
370
		__u8 wheel;
371
	} __packed * pad_report = (struct pad_report *)data;
372

373
	if (!data)
374
		return 0; /* EPERM check */
375

376
	/* Report ID 1 - Keyboard events (button presses) */
377
	if (data[0] == BT_PAD_KBD_REPORT_ID) {
378
		const __u8 button_mapping[] = {
379
			0x0e, /* Button 1:  K */
380
			0x0a, /* Button 2:  G */
381
			0x0f, /* Button 3:  L */
382
			0x4c, /* Button 4:  Delete */
383
			0x0c, /* Button 5:  I */
384
			0x07, /* Button 6:  D */
385
			0x05, /* Button 7:  B */
386
			0x08, /* Button 8:  E */
387
			0x16, /* Button 9:  S */
388
			0x1d, /* Button 10: Z */
389
			0x06, /* Button 11: C */
390
			0x19, /* Button 12: V */
391
			0xff, /* Button 13: LeftControl */
392
			0xff, /* Button 14: LeftAlt */
393
			0xff, /* Button 15: LeftShift */
394
			0x28, /* Button 16: Return Enter */
395
			0x2c, /* Button 17: Spacebar */
396
			0x11, /* Button 18: N */
397
		};
398

399
		__u8 modifiers = data[1];
400
		__u32 buttons = 0;
401

402
		if (modifiers & 0x01) { /* Control */
403
			buttons |= BIT(12);
404
		}
405
		if (modifiers & 0x02) { /* Shift */
406
			buttons |= BIT(14);
407
		}
408
		if (modifiers & 0x04) { /* Alt */
409
			buttons |= BIT(13);
410
		}
411

412
		for (int i = 4; i < BT_PAD_KBD_REPORT_LENGTH; i++) {
413
			if (!data[i])
414
				break;
415

416
			for (size_t b = 0; b < ARRAY_SIZE(button_mapping); b++) {
417
				if (data[i] != 0xff && data[i] == button_mapping[b]) {
418
					buttons |= BIT(b);
419
					break;
420
				}
421
			}
422
		}
423

424
		last_button_state = buttons;
425

426
		pad_report->report_id = OUR_REPORT_ID;
427
		pad_report->btn_stylus = 0;
428
		pad_report->x = 0;
429
		pad_report->y = 0;
430
		pad_report->buttons = buttons;
431
		pad_report->wheel = 0;
432

433
		return sizeof(struct pad_report);
434
	}
435

436
	/* Report ID 2 - Consumer control events (the button inside the wheel) */
437
	if (data[0] == BT_PAD_CC_REPORT_ID) {
438
		const __u8 PlayPause = 0xcd;
439

440
		if (data[1] == PlayPause)
441
			last_button_state |= BIT(18);
442
		else
443
			last_button_state &= ~BIT(18);
444

445
		pad_report->report_id = OUR_REPORT_ID;
446
		pad_report->btn_stylus = 0;
447
		pad_report->x = 0;
448
		pad_report->y = 0;
449
		pad_report->buttons = last_button_state;
450
		pad_report->wheel = 0;
451

452
		return sizeof(struct pad_report);
453
	}
454

455
	/* Report ID 5 - Mouse events (wheel rotation) */
456
	if (data[0] == BT_PAD_MOUSE_REPORT_ID) {
457
		__u8 wheel_delta = data[6];
458

459
		pad_report->report_id = OUR_REPORT_ID;
460
		pad_report->btn_stylus = 0;
461
		pad_report->x = 0;
462
		pad_report->y = 0;
463
		pad_report->buttons = last_button_state;
464
		pad_report->wheel = wheel_delta;
465

466
		return sizeof(struct pad_report);
467
	}
468

469
	return 0;
470
}
471

472
HID_BPF_OPS(keydial_k20_bluetooth) = {
473
	.hid_device_event = (void *)k20_bt_fix_events,
474
	.hid_rdesc_fixup = (void *)k20_bt_fix_rdesc,
475
};
476

477
SEC("syscall")
478
int probe(struct hid_bpf_probe_args *ctx)
479
{
480
	switch (ctx->rdesc_size) {
481
	case BT_PAD_REPORT_DESCRIPTOR_LENGTH:
482
	case BT_PUCK_REPORT_DESCRIPTOR_LENGTH:
483
		ctx->retval = 0;
484
		break;
485
	default:
486
		ctx->retval = -EINVAL;
487
	}
488

489
	return 0;
490
}
491

492
char _license[] SEC("license") = "GPL";
493

494
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