On Thu, Jun 15, 2017 at 07:33:58AM +0000, Zheng, Lv wrote: > Hi, Peter > > > From: Peter Hutterer [mailto:peter.hutterer@xxxxxxxxx] > > Subject: Re: [systemd-devel] [WIP PATCH 0/4] Rework the unreliable LID switch exported by ACPI > > > > On Thu, Jun 15, 2017 at 02:52:57AM +0000, Zheng, Lv wrote: > > > Hi, Benjamin > > > > > > > From: Benjamin Tissoires [mailto:benjamin.tissoires@xxxxxxxxxx] > > > > 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@xxxxxxxxxx) 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". > > > > Sorry, can you clarify this bit please? I'm not sure what you mean here. > > Note that there's an unknown amount of time between "device node appearing > > in the system" and when a userspace process actually opens it and looks at > > its state. By then, the node may have changed state again. > > We can see: > "logind" has already implemented a timeout, and will not respond lid state > unless it can be stable within this timeout period. > I'm not an expert of logind, maybe this is because of "HoldOffTimeoutSec"? > > I feel "removing the input node for a period where its state is not trustful" > is technically identical to this mechanism. but you'd be making kernel policy based on one userspace implementation. e.g. libinput doesn't have a timeout period, it assumes the state is correct when an input node is present. Cheers, Peter -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
