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Message-ID: <Z02jHuRaDGfObqlV@duo.ucw.cz>
Date: Mon, 2 Dec 2024 13:07:58 +0100
From: Pavel Machek <pavel@...x.de>
To: Sasha Levin <sashal@...nel.org>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Benjamin Tissoires <bentiss@...nel.org>,
	Tatsuyuki Ishi <ishitatsuyuki@...il.com>,
	Jiri Kosina <jkosina@...e.com>, jikos@...nel.org,
	linux-input@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 4.19 4/4] HID: bpf: Fix NKRO on Mistel MD770

Hi!

> From: Benjamin Tissoires <bentiss@...nel.org>
> 
> [ 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";

-- 
DENX Software Engineering GmbH,        Managing Director: Erika Unter
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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