Hi!
> From: Benjamin Tissoires <bentiss@xxxxxxxxxx>
>
> [ Upstream commit 9bc089307e8dff7797233308372b4a90ce8f79be ]
>
> Mistel MD770 keyboard (using Holtek Semiconductor, Inc. controller) has
> a quirk in report descriptor in one of its interfaces (more detail in
> the source file). Fix up the descriptor to allow NKRO to work again.
>
> Tested by loading the BPF program and confirming that 8 simultaneous
> keypresses work.
Ummm. No. drivers/hid/bpf/progs/ not existing in 4.19 should be a
hint.
Best regards,
Pavel
> +++ b/drivers/hid/bpf/progs/Mistel__MD770.bpf.c
> @@ -0,0 +1,154 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2024 Tatsuyuki Ishi
> + */
> +
> +#include "vmlinux.h"
> +#include "hid_bpf.h"
> +#include "hid_bpf_helpers.h"
> +#include <bpf/bpf_tracing.h>
> +
> +#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";
--
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