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Subject: Re: [PATCH 1/2] platform/x86: asus-wmi: Call new led hw_changed API
 on kbd brightness change
To:     Benjamin Berg <benjamin@sipsolutions.net>,
        Chris Chiu <chiu@endlessm.com>
Cc:     Bastien Nocera <hadess@hadess.net>,
        Darren Hart <dvhart@infradead.org>,
        Daniel Drake <drake@endlessm.com>,
        Corentin Chary <corentin.chary@gmail.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Platform Driver <platform-driver-x86@vger.kernel.org>,
        acpi4asus-user <acpi4asus-user@lists.sourceforge.net>,
        Linux Upstreaming Team <linux@endlessm.com>
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From:   Hans de Goede <hdegoede@redhat.com>
Message-ID: <173fdeb2-8129-57eb-fe2e-3ae16eec54b6@redhat.com>
Date:   Wed, 6 Jun 2018 17:32:52 +0200
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Hi,

On 06-06-18 16:27, Benjamin Berg wrote:
> Hi,
> 
> On Wed, 2018-06-06 at 10:50 +0800, Chris Chiu wrote:
>> On Tue, Jun 5, 2018 at 7:06 PM, Hans de Goede <hdegoede@redhat.com>
>> wrote:
>>> Hi,
>>>
>>>
>>> On 05-06-18 12:46, Benjamin Berg wrote:
>>>>
>>>> Hey,
>>>>
>>>> On Tue, 2018-06-05 at 12:31 +0200, Hans de Goede wrote:
>>>>>
>>>>> On 05-06-18 12:14, Bastien Nocera wrote:
>>>>>>
>>>>>> On Tue, 2018-06-05 at 12:05 +0200, Hans de Goede wrote:
>>>>>>>
>>>>>>> On 05-06-18 11:58, Bastien Nocera wrote:
>>>>>>>>
>>>>>>>> [SNIP]
>>>>>>>
>>>>>>>
>>>>>>> Ok, so what are you suggestion, do you really want to
>>>>>>> hardcode
>>>>>>> the cycle behavior in the kernel as these 2 patches are
>>>>>>> doing,
>>>>>>> without any option to intervene from userspace?
>>>>>>>
>>>>>>> As mentioned before in the thread there are several example
>>>>>>> of the kernel deciding to handle key-presses itself,
>>>>>>> putting
>>>>>>> policy in the kernel and they have all ended poorly (think
>>>>>>> e.g. rfkill, acpi-video dealing with LC brightnesskey
>>>>>>> presses
>>>>>>> itself).
>>>>>>>
>>>>>>> I guess one thing we could do here is code out both
>>>>>>> solutions,
>>>>>>> have a module option which controls if we:
>>>>>>>
>>>>>>> 1) Handle this in the kernel as these patches do
>>>>>>> 2) Or send a new KEY_KBDILLUMCYCLE event
>>>>>>>
>>>>>>> Combined with a Kconfig option to select which is the
>>>>>>> default
>>>>>>> behavior. Then Endless can select 1 for now and then in
>>>>>>> Fedora (which defaults to Wayland now) we could default to
>>>>>>> 2. once all the code for handling 2 is in place.
>>>>>>>
>>>>>>> This is ugly (on the kernel side) but it might be the best
>>>>>>> compromise we can do.
>>>>>>
>>>>>>
>>>>>> I don't really mind which option is used, I'm listing the
>>>>>> problems with
>>>>>> the different options. If you don't care about Xorg, then
>>>>>> definitely go
>>>>>> for adding a new key. Otherwise, processing it in the kernel
>>>>>> is the
>>>>>> least ugly, especially given that the key goes through the
>>>>>> same driver
>>>>>> that controls the brightness anyway. There's no crazy cross
>>>>>> driver
>>>>>> interaction as there was in the other cases you listed.
>>>>>
>>>>>
>>>>> Unfortunately not caring about Xorg is not really an option.
>>>>>
>>>>> Ok, new idea, how about we make g-s-d behavior upon detecting a
>>>>> KEY_KBDILLUMTOGGLE event configurable, if we're on a Mac do a
>>>>> toggle, otherwise do a cycle.
>>>>>
>>>>> Or we could do this through hwdb, then we could add a hwdb entry
>>>>> for this laptop setting the udev property to do a cycle instead of
>>>>> a toggle on receiving the keypress.
>>>>
>>>> If we are adding hwdb entries anyway to control the userspace
>>>> interpretation of the TOGGLE key, then we could also add the new CYCLE
>>>> key and explicitly re-map it to TOGGLE. That requires slightly more
>>>> logic in hwdb, but it does mean that we could theoretically just drop
>>>> the workaround if we ever stop caring about Xorg.
>>>
>>> Hmm, interesting proposal, I say go for it :)
>>>
>>
>> So maybe the next stop is that I can follow Darren's suggestion to eliminate
>> the is_kbd_led_event() and send a v2 for review?
> 
> I believe the best compromise we have right now is to do what Hans
> suggested in an earlier proposal. That is implementing the two separate
> behaviours in the kernel
> 
>   1) handle this in the kernel as if the hardware changed it, and
>   2) send a new KEY_KBDILLUMCYCLE event [default].

I think you mean or, not and, depending on a module option the
code should do either 1) or 2) not both :)

Darren, Andy could you live with a module option for this?

> Which one is used would be a compile time option for the kernel.
> 
> Then we have three different choices for handling these devices from a
> userspace/distribution point of view:
>   1. Let the kernel handle these devices (quick fix)
>   2. Assume we are on wayland and handle KEY_KBDILLUMCYCLE
>      (great if Xorg support is not a requirement)

Ack, although 2 will require some work in userspace, teach
all the layers like xkb about the new KEY_KBDILLUMCYCLE and
teach g-s-d to listen to it and do the right thing. But long
term 2. is the correct solution, so it would be good to start
working towards this.

>   3. For Xorg support:
>      - Add hwdb entry
>      - remap key to KEY_KBDILLUMTOGGLE
>      - set a flag on the keyboard
>      - detect the flag in userspace and handle KEY_KBDILLUMTOGGLE
>        as if KEY_KBDILLUMCYCLE was pressed
>      (yep, quite ugly)

I would just use 1. for Xorg compat and not bother with this mess.

Regards,

Hans