linux-kernel - Re: [PATCH] HID: input: Increase maximum number of joystick buttons

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aa40f6010c721863c09673fc8801e0a382619d89.camel@gmail.com>
Date: Sat, 03 Jan 2026 20:26:55 +0100
From: tomasz.pakula.oficjalny@...il.com
To: Ivan Gorinov <linux-kernel@...imeter.info>, Jiri Kosina
 <jikos@...nel.org>
Cc: linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: input: Increase maximum number of joystick buttons

On Sat, 2025-12-20 at 19:41 +0000, Ivan Gorinov wrote:
> This patch increases the limit from 80 to 112 key codes.
> 
> If a joystick has 80 or fewer buttons, mapping stays the same.
> 
> If a joystick has more than 80 buttons:
> 
>   Map buttons [  0 ..  15 ] to key codes starting with BTN_JOYSTICK;
>   Map buttons [ 16 ..  47 ] to key codes starting with KEY_MACRO1;
>   Map buttons [ 48 .. 111 ] to key codes starting with BTN_TRIGGER_HAPPY.
> 
> Signed-off-by: Ivan Gorinov <linux-kernel@...imeter.info>
> ---
>  drivers/hid/hid-input.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> index 2633fcd8f910..c6159f96de04 100644
> --- a/drivers/hid/hid-input.c
> +++ b/drivers/hid/hid-input.c
> @@ -763,7 +763,13 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
>  				if (code <= 0xf)
>  					code += BTN_JOYSTICK;
>  				else
> -					code += BTN_TRIGGER_HAPPY - 0x10;
> +					if (field->maxusage <= 80)
> +						code += BTN_TRIGGER_HAPPY - 0x10;
> +					else
> +						if (code <= 0x2f)
> +							code += KEY_MACRO1 - 0x10;
> +						else
> +							code += BTN_TRIGGER_HAPPY - 0x30;
>  				break;
>  		case HID_GD_GAMEPAD:
>  				if (code <= 0xf)

As stated previously by Dmitry when I tried to increase the KEY_MAX for
the same reason, the defined usages have their place and shouldn't be
misused. I finally understood that and I have to say that this is just
more confusing and a dirty hack, certainly used by some drivers because
it still works with SDL and Wine (they only care about the usage index).

I'm working on a proper solution with a new event type that will only
send button number (starting from 1 as does plain HID) and it's value.

This will support up to 65535 (u16) buttons and should be enough for
years to come :D I'll make sure to CC you when I'll send RFC.