drivers/hid/bpf/progs/Mistel__MD770.bpf.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright (c) 2024 Tatsuyuki Ishi
   3  */
   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_HOLTEK      0x04D9
  11 #define PID_MD770       0x0339
  12 #define RDESC_SIZE      203
  13
  14 HID_BPF_CONFIG(
  15         HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_HOLTEK, PID_MD770)
  16 );
  17
  18 /*
  19  * The Mistel MD770 keyboard reports the first 6 simultaneous key presses
  20  * through the first interface, and anything beyond that through a second
  21  * interface. Unfortunately, the second interface's report descriptor has an
  22  * error, causing events to be malformed and ignored. This HID-BPF driver
  23  * fixes the descriptor to allow NKRO to work again.
  24  *
  25  * For reference, this is the original report descriptor:
  26  *
  27  * 0x05, 0x01,        // Usage Page (Generic Desktop)        0
  28  * 0x09, 0x80,        // Usage (System Control)              2
  29  * 0xa1, 0x01,        // Collection (Application)            4
  30  * 0x85, 0x01,        //  Report ID (1)                      6
  31  * 0x19, 0x81,        //  Usage Minimum (129)                8
  32  * 0x29, 0x83,        //  Usage Maximum (131)                10
  33  * 0x15, 0x00,        //  Logical Minimum (0)                12
  34  * 0x25, 0x01,        //  Logical Maximum (1)                14
  35  * 0x95, 0x03,        //  Report Count (3)                   16
  36  * 0x75, 0x01,        //  Report Size (1)                    18
  37  * 0x81, 0x02,        //  Input (Data,Var,Abs)               20
  38  * 0x95, 0x01,        //  Report Count (1)                   22
  39  * 0x75, 0x05,        //  Report Size (5)                    24
  40  * 0x81, 0x01,        //  Input (Cnst,Arr,Abs)               26
  41  * 0xc0,              // End Collection                      28
  42  * 0x05, 0x0c,        // Usage Page (Consumer Devices)       29
  43  * 0x09, 0x01,        // Usage (Consumer Control)            31
  44  * 0xa1, 0x01,        // Collection (Application)            33
  45  * 0x85, 0x02,        //  Report ID (2)                      35
  46  * 0x15, 0x00,        //  Logical Minimum (0)                37
  47  * 0x25, 0x01,        //  Logical Maximum (1)                39
  48  * 0x95, 0x12,        //  Report Count (18)                  41
  49  * 0x75, 0x01,        //  Report Size (1)                    43
  50  * 0x0a, 0x83, 0x01,  //  Usage (AL Consumer Control Config) 45
  51  * 0x0a, 0x8a, 0x01,  //  Usage (AL Email Reader)            48
  52  * 0x0a, 0x92, 0x01,  //  Usage (AL Calculator)              51
  53  * 0x0a, 0x94, 0x01,  //  Usage (AL Local Machine Browser)   54
  54  * 0x09, 0xcd,        //  Usage (Play/Pause)                 57
  55  * 0x09, 0xb7,        //  Usage (Stop)                       59
  56  * 0x09, 0xb6,        //  Usage (Scan Previous Track)        61
  57  * 0x09, 0xb5,        //  Usage (Scan Next Track)            63
  58  * 0x09, 0xe2,        //  Usage (Mute)                       65
  59  * 0x09, 0xea,        //  Usage (Volume Down)                67
  60  * 0x09, 0xe9,        //  Usage (Volume Up)                  69
  61  * 0x0a, 0x21, 0x02,  //  Usage (AC Search)                  71
  62  * 0x0a, 0x23, 0x02,  //  Usage (AC Home)                    74
  63  * 0x0a, 0x24, 0x02,  //  Usage (AC Back)                    77
  64  * 0x0a, 0x25, 0x02,  //  Usage (AC Forward)                 80
  65  * 0x0a, 0x26, 0x02,  //  Usage (AC Stop)                    83
  66  * 0x0a, 0x27, 0x02,  //  Usage (AC Refresh)                 86
  67  * 0x0a, 0x2a, 0x02,  //  Usage (AC Bookmarks)               89
  68  * 0x81, 0x02,        //  Input (Data,Var,Abs)               92
  69  * 0x95, 0x01,        //  Report Count (1)                   94
  70  * 0x75, 0x0e,        //  Report Size (14)                   96
  71  * 0x81, 0x01,        //  Input (Cnst,Arr,Abs)               98
  72  * 0xc0,              // End Collection                      100
  73  * 0x05, 0x01,        // Usage Page (Generic Desktop)        101
  74  * 0x09, 0x02,        // Usage (Mouse)                       103
  75  * 0xa1, 0x01,        // Collection (Application)            105
  76  * 0x09, 0x01,        //  Usage (Pointer)                    107
  77  * 0xa1, 0x00,        //  Collection (Physical)              109
  78  * 0x85, 0x03,        //   Report ID (3)                     111
  79  * 0x05, 0x09,        //   Usage Page (Button)               113
  80  * 0x19, 0x01,        //   Usage Minimum (1)                 115
  81  * 0x29, 0x08,        //   Usage Maximum (8)                 117
  82  * 0x15, 0x00,        //   Logical Minimum (0)               119
  83  * 0x25, 0x01,        //   Logical Maximum (1)               121
  84  * 0x75, 0x01,        //   Report Size (1)                   123
  85  * 0x95, 0x08,        //   Report Count (8)                  125
  86  * 0x81, 0x02,        //   Input (Data,Var,Abs)              127
  87  * 0x05, 0x01,        //   Usage Page (Generic Desktop)      129
  88  * 0x09, 0x30,        //   Usage (X)                         131
  89  * 0x09, 0x31,        //   Usage (Y)                         133
  90  * 0x16, 0x01, 0x80,  //   Logical Minimum (-32767)          135
  91  * 0x26, 0xff, 0x7f,  //   Logical Maximum (32767)           138
  92  * 0x75, 0x10,        //   Report Size (16)                  141
  93  * 0x95, 0x02,        //   Report Count (2)                  143
  94  * 0x81, 0x06,        //   Input (Data,Var,Rel)              145
  95  * 0x09, 0x38,        //   Usage (Wheel)                     147
  96  * 0x15, 0x81,        //   Logical Minimum (-127)            149
  97  * 0x25, 0x7f,        //   Logical Maximum (127)             151
  98  * 0x75, 0x08,        //   Report Size (8)                   153
  99  * 0x95, 0x01,        //   Report Count (1)                  155
 100  * 0x81, 0x06,        //   Input (Data,Var,Rel)              157
 101  * 0x05, 0x0c,        //   Usage Page (Consumer Devices)     159
 102  * 0x0a, 0x38, 0x02,  //   Usage (AC Pan)                    161
 103  * 0x95, 0x01,        //   Report Count (1)                  164
 104  * 0x81, 0x06,        //   Input (Data,Var,Rel)              166
 105  * 0xc0,              //  End Collection                     168
 106  * 0xc0,              // End Collection                      169
 107  * 0x05, 0x01,        // Usage Page (Generic Desktop)        170
 108  * 0x09, 0x06,        // Usage (Keyboard)                    172
 109  * 0xa1, 0x01,        // Collection (Application)            174
 110  * 0x85, 0x04,        //  Report ID (4)                      176
 111  * 0x05, 0x07,        //  Usage Page (Keyboard)              178
 112  * 0x95, 0x01,        //  Report Count (1)                   180
 113  * 0x75, 0x08,        //  Report Size (8)                    182
 114  * 0x81, 0x03,        //  Input (Cnst,Var,Abs)               184
 115  * 0x95, 0xe8,        //  Report Count (232)                 186
 116  * 0x75, 0x01,        //  Report Size (1)                    188
 117  * 0x15, 0x00,        //  Logical Minimum (0)                190
 118  * 0x25, 0x01,        //  Logical Maximum (1)                192
 119  * 0x05, 0x07,        //  Usage Page (Keyboard)              194
 120  * 0x19, 0x00,        //  Usage Minimum (0)                  196
 121  * 0x29, 0xe7,        //  Usage Maximum (231)                198
 122  * 0x81, 0x00,        //  Input (Data,Arr,Abs)               200  <- change to 0x81, 0x02 (Data,Var,Abs)
 123  * 0xc0,              // End Collection                      202
 124  */
 125
 126 SEC(HID_BPF_RDESC_FIXUP)
 127 int BPF_PROG(hid_rdesc_fixup_mistel_md770, struct hid_bpf_ctx *hctx)
 128 {
 129         __u8 *data = hid_bpf_get_data(hctx, 0, HID_MAX_DESCRIPTOR_SIZE);
 130
 131         if (!data)
 132                 return 0; /* EPERM check */
 133
 134         if (data[201] == 0x00)
 135                 data[201] = 0x02;
 136
 137         return 0;
 138 }
 139
 140 HID_BPF_OPS(mistel_md770) = {
 141         .hid_rdesc_fixup = (void *)hid_rdesc_fixup_mistel_md770,
 142 };
 143
 144 SEC("syscall")
 145 int probe(struct hid_bpf_probe_args *ctx)
 146 {
 147         ctx->retval = ctx->rdesc_size != RDESC_SIZE;
 148         if (ctx->retval)
 149                 ctx->retval = -EINVAL;
 150
 151         return 0;
 152 }
 153
 154 char _license[] SEC("license") = "GPL";