Messages in this thread | | | Subject | Re: [PATCH v4 0/7] Support inhibiting input devices | From | Hans de Goede <> | Date | Wed, 10 Jun 2020 15:52:15 +0200 |
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Hi,
On 6/10/20 12:38 PM, Rafael J. Wysocki wrote: > On Wed, Jun 10, 2020 at 11:50 AM Hans de Goede <hdegoede@redhat.com> wrote:
<snip>
>> A different, but related issue is how to make devices actually use the >> new inhibit support on the builtin keyboard + touchpad when say the lid >> is closed. Arguably this is an userspace problem, but it is a tricky >> one. Currently on most modern Linux distributions suspend-on-lid-close >> is handled by systemd-logind and most modern desktop-environments are >> happy to have logind handle this for them. >> >> But most knowledge about input devices and e.g. heurisitics to decide >> if a touchpad is internal or external are part of libinput. Now we could >> have libinput use the new inhibit support (1), but then when the lid >> closes we get race between whatever process is using libinput trying >> to inhibit the touchpad (which must be done before to suspend to disable >> it as wakeup source) and logind trying to suspend the system. >> >> One solution here would be to move the setting of the inhibit sysfs >> attr into logind, but that requires adding a whole bunch of extra >> knowledge to logind which does not really belong there IMHO. >> >> I've been thinking a bit about this and to me it seems that the kernel >> is in the ideal position to automatically inhibit some devices when >> some EV_SW transitions from 0->1 (and uninhibit again on 1->0). The >> issue here is to chose on which devices to enable this. I believe >> that the auto inhibit on some switches mechanism is best done inside >> the kernel (disabled by default) and then we can have a sysfs >> attr called auto_inhibit_ev_sw_mask which can be set to e.g. >> (1 << SW_LID) to make the kernel auto-inhibit the input-device whenever >> the lid is closed, or to ((1 << SW_LID) | (1 << SW_TABLET_MODE)) to >> inhibit both when the lid is closed or when switched to tablet mode. > > I agree that the kernel is the right place to handle this, but it > requires some extra knowledge about dependencies between devices. > > It'd be kind of like power resources in ACPI, so for each state of a > "master" device (in principle, there may be more states of it than > just two) there would be a list of "dependent" intput devices that > need to be inhibited when the "master" device goes into that state.
So a big part of the reason to punt the decision on which input devices to enable this auto-inhibit is that we don't really have information about those relationsships / device-links you are suggesting here. libinput is already doing inhibiting inside userspace for e.g. the tablet-mode switch but it relies on heuristics + quirk tables to decide which keyboards should be inhibited and which not.
E.g. for a 360 degree hinges 2-in-1 we want to disable the builtin keyboard, when folded into in tablet mode, but not any external ones.
Mostly the builtin kbd will be PS2 but I have one such 2-in-1 here in my home office with a USB kbd ...
In general of the master devices there will be only 1, there will be only 1 lid switch and only 1 tablet-mode switch. So my idea with the auto_inhibit_ev_sw_mask, is for it to be a per input-device setting.
So using your terms, all input devices with the (1 << SW_LID) bit set in their auto_inhibit_ev_sw_mask will be dependents of the (master) device which actually is reporting the SW_LID bit.
The idea here is for this to work the same as how the rfkill code from net/rfkill/input.c works, except instead of binding e.g. KEY_WLAN to toggling the sw-state of rfkill devices with a type of RFKILL_TYPE_WLAN. This will bind SW_LID to inhibiting input devices with the SW_LID bit set in their auto_inhibit_ev_sw_mask.
Regards,
Hans
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