Re: [PATCH v3 1/2] ACPI / button: Add KEY_LID_CLOSE for new usage model

From: Bastien Nocera
Date: Mon Jul 18 2016 - 11:51:45 EST

On Mon, 2016-07-18 at 09:53 +0200, Benjamin Tissoires wrote:
> I don't think this is a good solution to have a kernel parameter. I
> thought the final decision were to have userspace decide which event
> was valid, and so we just need to export and emit both of events.
> _If_ you export a kernel parameter, it makes sense to have a dmi
> blacklist to have a good default experience, which is what you wanted
> to avoid.
> So if you just export and use both events at the same time, you will
> have:
> - correct ACPI machines will just have an extra KEY_LID_CLOSE event
> emitted, which will not harm logind
> - wrong ACPI machines will not have their SW_LID input event updated
> because it will be kept closed. But given that logind will ignore it,
> there is no harm either
> As Dmitry said, we could also have a KEY_LID_OPEN emitted for
> symmetrical purposes, but I am not entirely sure if this will confuse
> userspace or not. On the other hand, there are few users of these
> states, and we can teach them how to properly use them.
> So in the end, I think you should just get rid of the kernel
> parameter, export SW_LID, KEY_LID_CLOSE, KEY_LID_OPEN in the event
> node, and only add the KEY_LID_CLOSE|OPEN events on an actual acpi
> notification.
> Then a small hwdb entry set will teach logind/powerd if they need to
> ignore the SW_LID event or not.

So user-space would have its own blacklist (likely in udev through an
hwdb), instead of having it in the kernel? That seems like a fine idea
to me, and one of the first consumers, logind, would have all the
necessary data straight away.