linux-kernel - Re: [PATCH AUTOSEL 4.19 3/3] HID: bpf: add in-tree HID-BPF fix for the HP Elite Presenter Mouse

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Date: Mon, 27 May 2024 16:44:29 +0200
From: Benjamin Tissoires <bentiss@...nel.org>
To: Sasha Levin <sashal@...nel.org>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org, 
	Peter Hutterer <peter.hutterer@...-t.net>, jikos@...nel.org, linux-input@...r.kernel.org, 
	bpf@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 4.19 3/3] HID: bpf: add in-tree HID-BPF fix for
 the HP Elite Presenter Mouse

On May 27 2024, Sasha Levin wrote:
> From: Benjamin Tissoires <bentiss@...nel.org>
> 
> [ Upstream commit 4e6d2a297dd5be26ad409b7a05b20bd033d1c95e ]
> 
> Duplicate of commit 0db117359e47 ("HID: add quirk for 03f0:464a HP Elite
> Presenter Mouse"), but in a slightly better way.
> 
> This time we actually change the application collection, making clearer
> for userspace what the second mouse is.
> 
> Note that having both hid-quirks fix and this HID-BPF fix is not a
> problem at all.

Please drop this patch in all backports (and FWIW, any fix in drivers/hid/bpf/progs/).

HID-BPF is only available since kernel v6.3, and the compilation output
of the in-tree file is not used directly, but shipped from udev-hid-bpf.

TL;DR: this just adds noise to those stable kernel trees.

Cheers,
Benjamin

> 
> Link: https://lore.kernel.org/r/20240410-bpf_sources-v1-4-a8bf16033ef8@kernel.org
> Reviewed-by: Peter Hutterer <peter.hutterer@...-t.net>
> Signed-off-by: Benjamin Tissoires <bentiss@...nel.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  .../hid/bpf/progs/HP__Elite-Presenter.bpf.c   | 58 +++++++++++++++++++
>  1 file changed, 58 insertions(+)
>  create mode 100644 drivers/hid/bpf/progs/HP__Elite-Presenter.bpf.c
> 
> diff --git a/drivers/hid/bpf/progs/HP__Elite-Presenter.bpf.c b/drivers/hid/bpf/progs/HP__Elite-Presenter.bpf.c
> new file mode 100644
> index 0000000000000..3d14bbb6f2762
> --- /dev/null
> +++ b/drivers/hid/bpf/progs/HP__Elite-Presenter.bpf.c
> @@ -0,0 +1,58 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2023 Benjamin Tissoires
> + */
> +
> +#include "vmlinux.h"
> +#include "hid_bpf.h"
> +#include "hid_bpf_helpers.h"
> +#include <bpf/bpf_tracing.h>
> +
> +#define VID_HP 0x03F0
> +#define PID_ELITE_PRESENTER 0x464A
> +
> +HID_BPF_CONFIG(
> +	HID_DEVICE(BUS_BLUETOOTH, HID_GROUP_GENERIC, VID_HP, PID_ELITE_PRESENTER)
> +);
> +
> +/*
> + * Already fixed as of commit 0db117359e47 ("HID: add quirk for 03f0:464a
> + * HP Elite Presenter Mouse") in the kernel, but this is a slightly better
> + * fix.
> + *
> + * The HP Elite Presenter Mouse HID Record Descriptor shows
> + * two mice (Report ID 0x1 and 0x2), one keypad (Report ID 0x5),
> + * two Consumer Controls (Report IDs 0x6 and 0x3).
> + * Prior to these fixes it registers one mouse, one keypad
> + * and one Consumer Control, and it was usable only as a
> + * digital laser pointer (one of the two mouses).
> + * We replace the second mouse collection with a pointer collection,
> + * allowing to use the device both as a mouse and a digital laser
> + * pointer.
> + */
> +
> +SEC("fmod_ret/hid_bpf_rdesc_fixup")
> +int BPF_PROG(hid_fix_rdesc, struct hid_bpf_ctx *hctx)
> +{
> +	__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 4096 /* size */);
> +
> +	if (!data)
> +		return 0; /* EPERM check */
> +
> +	/* replace application mouse by application pointer on the second collection */
> +	if (data[79] == 0x02)
> +		data[79] = 0x01;
> +
> +	return 0;
> +}
> +
> +SEC("syscall")
> +int probe(struct hid_bpf_probe_args *ctx)
> +{
> +	ctx->retval = ctx->rdesc_size != 264;
> +	if (ctx->retval)
> +		ctx->retval = -EINVAL;
> +
> +	return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> -- 
> 2.43.0
>