linux-kernel - RE: [systemd-devel] [WIP PATCH 0/4] Rework the unreliable LID switch exported by ACPI

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Date:   Thu, 15 Jun 2017 02:52:57 +0000
From:   "Zheng, Lv" <lv.zheng@...el.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Lennart Poettering <mzxreary@...inter.de>
CC:     "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        "Brown, Len" <len.brown@...el.com>, Lv Zheng <zetalog@...il.com>,
        Peter Hutterer <peter.hutterer@...-t.net>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "systemd-devel@...ts.freedesktop.org" 
        <systemd-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>
Subject: RE: [systemd-devel] [WIP PATCH 0/4] Rework the unreliable LID
 switch exported by ACPI

Hi, Benjamin

> From: Benjamin Tissoires [mailto:benjamin.tissoires@...hat.com]
> Subject: Re: [systemd-devel] [WIP PATCH 0/4] Rework the unreliable LID switch exported by ACPI
> 
> Hi,
> 
> [Sorry for the delay, I have been sidetracked from this]
> 
> On Jun 07 2017 or thereabouts, Lennart Poettering wrote:
> > On Thu, 01.06.17 20:46, Benjamin Tissoires (benjamin.tissoires@...hat.com) wrote:
> >
> > > Hi,
> > >
> > > Sending this as a WIP as it still need a few changes, but it mostly works as
> > > expected (still not fully compliant yet).
> > >
> > > So this is based on Lennart's comment in [1]: if the LID state is not reliable,
> > > the kernel should not export the LID switch device as long as we are not sure
> > > about its state.
> >
> > Ah nice! I (obviously) like this approach.
> 
> Heh. Now I just need to convince Lv that it's the right approach.

I feel we don't have big conflicts.
And I already took part of your idea into this patchset:
https://patchwork.kernel.org/patch/9771121/
https://patchwork.kernel.org/patch/9771119/
I tested my surface pros with Ubuntu, they are working as expected.

> > > Note that systemd currently doesn't sync the state when the input node just
> > > appears. This is a systemd bug, and it should not be handled by the kernel
> > > community.
> >
> > Uh if this is borked, we should indeed fix this in systemd. Is there
> > already a systemd github bug about this? If not, please create one,
> > and we'll look into it!
> 
> I don't think there is. I haven't raised it yet because I am not so sure
> this will not break again those worthless unreliable LID, and if we play
> whack a mole between the kernel and user space, things are going to be
> nasty. So I'd rather have this fixed in systemd along with the
> unreliable LID switch knowledge, so we are sure that the kernel behaves
> the way we expect it to be.

This is my feeling:
We needn't go that far.
We can interpret "input node appears" into "default input node state".
That's what you want for acpi button driver - we now defaults to "method" mode.

What's your opinion?

Thanks
Lv