linux-kernel - Re: [PATCH 1/2] platform/x86: asus-wmi: Call new led hw

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Date:   Tue, 5 Jun 2018 13:06:02 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Benjamin Berg <benjamin@...solutions.net>,
        Bastien Nocera <hadess@...ess.net>,
        Chris Chiu <chiu@...lessm.com>,
        Darren Hart <dvhart@...radead.org>
Cc:     Daniel Drake <drake@...lessm.com>,
        Corentin Chary <corentin.chary@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        acpi4asus-user <acpi4asus-user@...ts.sourceforge.net>,
        Linux Upstreaming Team <linux@...lessm.com>
Subject: Re: [PATCH 1/2] platform/x86: asus-wmi: Call new led hw_changed API
 on kbd brightness change

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 :)

Regards,

Hans