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

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Message-ID: <20260104004831.GA5238@altimeter-info>
Date: Sun, 4 Jan 2026 00:48:31 +0000
From: Ivan Gorinov <linux-kernel@...imeter.info>
To: tomasz.pakula.oficjalny@...il.com
Cc: Jiri Kosina <jikos@...nel.org>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: input: Increase maximum number of joystick buttons

On Sat, Jan 03, 2026 at 08:26:55PM +0100, tomasz.pakula.oficjalny@...il.com wrote:
> 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.
> > 
> 
> 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.

Thank you! I learned how to map more than 80 buttons by overriding function
hid_driver.input_mapping from your contribution to JacKeTUs/universal-pdiff
and used the same idea in my recent changes in the hid-winwing module.

Good luck in your work on new event type!
I will test your changes with my Orion2/TGRIP-18 combo.

Meanwhile, this patch could allow existing software (for example, X-Plane 12)
to work with more input devices without any changes in userspace.