// SPDX-License-Identifier: GPL-2.0 /* Copyright (c) 2024 Tatsuyuki Ishi */ #include "vmlinux.h" #include "hid_bpf.h" #include "hid_bpf_helpers.h" #include #define VID_HOLTEK 0x04D9 #define PID_MD770 0x0339 #define RDESC_SIZE 203 HID_BPF_CONFIG( HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_HOLTEK, PID_MD770) ); /* * The Mistel MD770 keyboard reports the first 6 simultaneous key presses * through the first interface, and anything beyond that through a second * interface. Unfortunately, the second interface's report descriptor has an * error, causing events to be malformed and ignored. This HID-BPF driver * fixes the descriptor to allow NKRO to work again. * * For reference, this is the original report descriptor: * * 0x05, 0x01, // Usage Page (Generic Desktop) 0 * 0x09, 0x80, // Usage (System Control) 2 * 0xa1, 0x01, // Collection (Application) 4 * 0x85, 0x01, // Report ID (1) 6 * 0x19, 0x81, // Usage Minimum (129) 8 * 0x29, 0x83, // Usage Maximum (131) 10 * 0x15, 0x00, // Logical Minimum (0) 12 * 0x25, 0x01, // Logical Maximum (1) 14 * 0x95, 0x03, // Report Count (3) 16 * 0x75, 0x01, // Report Size (1) 18 * 0x81, 0x02, // Input (Data,Var,Abs) 20 * 0x95, 0x01, // Report Count (1) 22 * 0x75, 0x05, // Report Size (5) 24 * 0x81, 0x01, // Input (Cnst,Arr,Abs) 26 * 0xc0, // End Collection 28 * 0x05, 0x0c, // Usage Page (Consumer Devices) 29 * 0x09, 0x01, // Usage (Consumer Control) 31 * 0xa1, 0x01, // Collection (Application) 33 * 0x85, 0x02, // Report ID (2) 35 * 0x15, 0x00, // Logical Minimum (0) 37 * 0x25, 0x01, // Logical Maximum (1) 39 * 0x95, 0x12, // Report Count (18) 41 * 0x75, 0x01, // Report Size (1) 43 * 0x0a, 0x83, 0x01, // Usage (AL Consumer Control Config) 45 * 0x0a, 0x8a, 0x01, // Usage (AL Email Reader) 48 * 0x0a, 0x92, 0x01, // Usage (AL Calculator) 51 * 0x0a, 0x94, 0x01, // Usage (AL Local Machine Browser) 54 * 0x09, 0xcd, // Usage (Play/Pause) 57 * 0x09, 0xb7, // Usage (Stop) 59 * 0x09, 0xb6, // Usage (Scan Previous Track) 61 * 0x09, 0xb5, // Usage (Scan Next Track) 63 * 0x09, 0xe2, // Usage (Mute) 65 * 0x09, 0xea, // Usage (Volume Down) 67 * 0x09, 0xe9, // Usage (Volume Up) 69 * 0x0a, 0x21, 0x02, // Usage (AC Search) 71 * 0x0a, 0x23, 0x02, // Usage (AC Home) 74 * 0x0a, 0x24, 0x02, // Usage (AC Back) 77 * 0x0a, 0x25, 0x02, // Usage (AC Forward) 80 * 0x0a, 0x26, 0x02, // Usage (AC Stop) 83 * 0x0a, 0x27, 0x02, // Usage (AC Refresh) 86 * 0x0a, 0x2a, 0x02, // Usage (AC Bookmarks) 89 * 0x81, 0x02, // Input (Data,Var,Abs) 92 * 0x95, 0x01, // Report Count (1) 94 * 0x75, 0x0e, // Report Size (14) 96 * 0x81, 0x01, // Input (Cnst,Arr,Abs) 98 * 0xc0, // End Collection 100 * 0x05, 0x01, // Usage Page (Generic Desktop) 101 * 0x09, 0x02, // Usage (Mouse) 103 * 0xa1, 0x01, // Collection (Application) 105 * 0x09, 0x01, // Usage (Pointer) 107 * 0xa1, 0x00, // Collection (Physical) 109 * 0x85, 0x03, // Report ID (3) 111 * 0x05, 0x09, // Usage Page (Button) 113 * 0x19, 0x01, // Usage Minimum (1) 115 * 0x29, 0x08, // Usage Maximum (8) 117 * 0x15, 0x00, // Logical Minimum (0) 119 * 0x25, 0x01, // Logical Maximum (1) 121 * 0x75, 0x01, // Report Size (1) 123 * 0x95, 0x08, // Report Count (8) 125 * 0x81, 0x02, // Input (Data,Var,Abs) 127 * 0x05, 0x01, // Usage Page (Generic Desktop) 129 * 0x09, 0x30, // Usage (X) 131 * 0x09, 0x31, // Usage (Y) 133 * 0x16, 0x01, 0x80, // Logical Minimum (-32767) 135 * 0x26, 0xff, 0x7f, // Logical Maximum (32767) 138 * 0x75, 0x10, // Report Size (16) 141 * 0x95, 0x02, // Report Count (2) 143 * 0x81, 0x06, // Input (Data,Var,Rel) 145 * 0x09, 0x38, // Usage (Wheel) 147 * 0x15, 0x81, // Logical Minimum (-127) 149 * 0x25, 0x7f, // Logical Maximum (127) 151 * 0x75, 0x08, // Report Size (8) 153 * 0x95, 0x01, // Report Count (1) 155 * 0x81, 0x06, // Input (Data,Var,Rel) 157 * 0x05, 0x0c, // Usage Page (Consumer Devices) 159 * 0x0a, 0x38, 0x02, // Usage (AC Pan) 161 * 0x95, 0x01, // Report Count (1) 164 * 0x81, 0x06, // Input (Data,Var,Rel) 166 * 0xc0, // End Collection 168 * 0xc0, // End Collection 169 * 0x05, 0x01, // Usage Page (Generic Desktop) 170 * 0x09, 0x06, // Usage (Keyboard) 172 * 0xa1, 0x01, // Collection (Application) 174 * 0x85, 0x04, // Report ID (4) 176 * 0x05, 0x07, // Usage Page (Keyboard) 178 * 0x95, 0x01, // Report Count (1) 180 * 0x75, 0x08, // Report Size (8) 182 * 0x81, 0x03, // Input (Cnst,Var,Abs) 184 * 0x95, 0xe8, // Report Count (232) 186 * 0x75, 0x01, // Report Size (1) 188 * 0x15, 0x00, // Logical Minimum (0) 190 * 0x25, 0x01, // Logical Maximum (1) 192 * 0x05, 0x07, // Usage Page (Keyboard) 194 * 0x19, 0x00, // Usage Minimum (0) 196 * 0x29, 0xe7, // Usage Maximum (231) 198 * 0x81, 0x00, // Input (Data,Arr,Abs) 200 <- change to 0x81, 0x02 (Data,Var,Abs) * 0xc0, // End Collection 202 */ SEC(HID_BPF_RDESC_FIXUP) int BPF_PROG(hid_rdesc_fixup_mistel_md770, struct hid_bpf_ctx *hctx) { __u8 *data = hid_bpf_get_data(hctx, 0, HID_MAX_DESCRIPTOR_SIZE); if (!data) return 0; /* EPERM check */ if (data[201] == 0x00) data[201] = 0x02; return 0; } HID_BPF_OPS(mistel_md770) = { .hid_rdesc_fixup = (void *)hid_rdesc_fixup_mistel_md770, }; SEC("syscall") int probe(struct hid_bpf_probe_args *ctx) { ctx->retval = ctx->rdesc_size != RDESC_SIZE; if (ctx->retval) ctx->retval = -EINVAL; return 0; } char _license[] SEC("license") = "GPL";