linux-kernel - Re: [PATCH v2] Input: xen-kbdfront

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Date:   Thu, 09 Mar 2023 17:09:05 +0100
From:   Mattijs Korpershoek <mkorpershoek@...libre.com>
To:     Jason Andryuk <jandryuk@...il.com>
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        Phillip Susi <phill@...susis.net>, stable@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input@...r.kernel.org
Subject: Re: [PATCH v2] Input: xen-kbdfront - drop keys to shrink modalias

Hi Jason,

On mer., mars 08, 2023 at 11:26, Jason Andryuk <jandryuk@...il.com> wrote:

> On Thu, Dec 15, 2022 at 8:54 AM Mattijs Korpershoek
> <mkorpershoek@...libre.com> wrote:
>>
>> On Fri, Dec 09, 2022 at 09:26, Jason Andryuk <jandryuk@...il.com> wrote:
>>
>> > xen kbdfront registers itself as being able to deliver *any* key since
>> > it doesn't know what keys the backend may produce.
>> >
>> > Unfortunately, the generated modalias gets too large and uevent creation
>> > fails with -ENOMEM.
>> >
>> > This can lead to gdm not using the keyboard since there is no seat
>> > associated [1] and the debian installer crashing [2].
>> >
>> > Trim the ranges of key capabilities by removing some BTN_* ranges.
>> > While doing this, some neighboring undefined ranges are removed to trim
>> > it further.
>> >
>> > An upper limit of KEY_KBD_LCD_MENU5 is still too large.  Use an upper
>> > limit of KEY_BRIGHTNESS_MENU.
>> >
>> > This removes:
>> > BTN_DPAD_UP(0x220)..BTN_DPAD_RIGHT(0x223)
>> > Empty space 0x224..0x229
>> >
>> > Empty space 0x28a..0x28f
>> > KEY_MACRO1(0x290)..KEY_MACRO30(0x2ad)
>> > KEY_MACRO_RECORD_START          0x2b0
>> > KEY_MACRO_RECORD_STOP           0x2b1
>> > KEY_MACRO_PRESET_CYCLE          0x2b2
>> > KEY_MACRO_PRESET1(0x2b3)..KEY_MACRO_PRESET3(0xb5)
>> > Empty space 0x2b6..0x2b7
>> > KEY_KBD_LCD_MENU1(0x2b8)..KEY_KBD_LCD_MENU5(0x2bc)
>> > Empty space 0x2bd..0x2bf
>> > BTN_TRIGGER_HAPPY(0x2c0)..BTN_TRIGGER_HAPPY40(0x2e7)
>> > Empty space 0x2e8..0x2ff
>> >
>> > The modalias shrinks from 2082 to 1550 bytes.
>> >
>> > A chunk of keys need to be removed to allow the keyboard to be used.
>> > This may break some functionality, but the hope is these macro keys are
>> > uncommon and don't affect any users.
>> >
>> > [1] https://github.com/systemd/systemd/issues/22944
>> > [2] https://lore.kernel.org/xen-devel/87o8dw52jc.fsf@vps.thesusis.net/T/
>> >
>> > Cc: Phillip Susi <phill@...susis.net>
>> > Cc: stable@...r.kernel.org
>> > Signed-off-by: Jason Andryuk <jandryuk@...il.com>
>>
>> Reviewed-by: Mattijs Korpershoek <mkorpershoek@...libre.com>
>
> Thank you, Mattjis.
>
> Any other thoughts?  Can this patch be applied?

That's not up to to decide, Dmitry might pick this up or give you a
review whenever he has time.

>
> Thanks,
> Jason