Hi, > From: Benjamin Tissoires [mailto:benjamin.tissoires@xxxxxxxxxx] > Subject: Re: [systemd-devel] [WIP PATCH 0/4] Rework the unreliable LID switch exported by ACPI > > On Jun 16 2017 or thereabouts, Zheng, Lv wrote: > > Hi, Benjamin > > > > Let me just say something one more time. > > > > > From: Benjamin Tissoires [mailto:benjamin.tissoires@xxxxxxxxxx] > > [snip] > > > > > > > > > > > > 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. > > > > > > > > Do you see practical issues? > > > > > > Yes, libinput can't rely on the LID switch information to disable > > > touchpads/touchscreens that are potentially sending false positive. > > > > "potential" doesn't mean "practical", right? > > I was using potential to say that some actual devices are sending > rightful states, while others are not (we already named them a lot in > those countless threads). So potential here is from a user space > perspective where you are not sure if the state is reliable or not > (given we currently don't have this information about reliability). > > > After applying my last version. > > There are no false-positives IMO. > > There are only delays for the reliable key events. > > ^^^^^^ > > While the "delay" is very common in computing world. > > No, if there is a delay, there is a false positive, because the initial > state is wrong with respect to the device physical state. > > > > > > > After resume, SW_LID state could remain unreliable "close" for a while. > > > > > > This is not an option. It is not part of the protocol, having an > > > unreliable state. > > > > > > > But that's just a kind of delay happens in all computing programs. > > > > I suppose all power managing programs have already handled that. > > > > I confirmed no breakage for systemd 233. > > > > For systemd 229, it cannot handle it well due to bugs. > > > > But my latest patch series has worked the bug around. > > > > So I don't see any breakage related to post-resume incorrect state period. > > > > Do you see problems that my tests haven't covered? > > > > > > The problems are that you are not following the protocol. And if systemd > > > 233 works around it, that's good, but systemd is not the only listener > > > of the LID switch input node, and you are still breaking those by > > > refusing to follow the specification of the evdev protocol. > > > > As you are talking about protocol, let me just ask once. > > > > In computing world, > > 1. delay is very common > > There are bus turnaround, network turnaround, ... > > Even measurement itself has delay described by Shannon sampling. > > Should the delay be a part of the protocol? > > Please, you are either trolling or just kidding. If there are delays in > the "computing world", these has to be handled by the kernel, and not > exported to the user space if the kernel protocol says that the state is > reliable. > > > 2. programs are acting according to rules (we call state machines) > > States are only determined after measurement (like "quantum states") > > I have Schroedinger's cat in my mind. > > Events are determined as they always occur after measurement to trigger "quantum jumps". > > So for EV_SW protocol, > > Should programs rely on the reliable "quantum jumps", > > Or should programs rely on the unreliable "quantum states"? > > No comments, this won't get us anywhere. > > > > > I think most UI programs care no about state stored in the input node, > > they only receive events raised from the input node. > > Bullshit. When you launch such a program, you need to query the state > because you won't receive the event that happened way before the launch. > > > Why should the kernel export a fade-in/fade-out input node to the UI programs and ask them to change? > > > > The only program that cares about the state stored in the input node is libinput. > > So why should every user program be changed to make libinput easier? > > No, all program that listen to LID switches input nodes care about the > state. We already told you that, you just don't listen: > > - systemd cares about the state as it does polling on the input node in > case it misses an event > - libinput cares about the state as previously mentioned > - gnome-setting-daemons cares about the state given it decides whether > or not lighting up the monitors depending on the state. And if you > relaunch the daemon, it'll query the state to decide what is the best > arrangement for the screens Let's consider this case with delay: After resume, gnome-setting-daemon queries SW_LID and got "close". Then it lights up the wrong monitors. Then I believe "open" will be delivered to it several seconds later. Should gnome-setting-daemon light-up correct monitors this time? So it just looks like user programs behave with a delay accordingly because of the "platform turnaround" delay. > - KDE should do the same (as it is not a daemon that can catch any > events) Cheers, Lv ��.n��������+%������w��{.n�����{��)��^n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
