[PATCH libinput 0/8] Add libinput_device_suspend() to disable devices

[Peter Hutterer]

On Mon, Sep 15, 2014 at 09:22:51AM +0200, Hans de Goede wrote:
> Hi,
> 
> On 09/15/2014 07:39 AM, Peter Hutterer wrote:
> > On Thu, Sep 11, 2014 at 04:34:48PM +0200, Bastien Nocera wrote:
> >> On Thu, 2014-08-21 at 16:18 +1000, Peter Hutterer wrote:
> >>> replying to myself, now that I've had a bit of a think about this all.
> >>>
> >>> On Wed, Aug 20, 2014 at 01:18:48PM +1000, Peter Hutterer wrote:
> >>>> This patchset adds two new API hooks, libinput_device_suspend() and
> >>>> libinput_device_resume() which do what it says on the box. No special event
> >>>> is sent when suspending or resuming, so this is really the hook to ignore a
> >>>> specific device.
> >>>>
> >>>> The main idea here is two-fold:
> >>>> some devices simply shouldn't send events, in which case suspending them
> >>>> means fewer wakeup calls. The other use-case is touchpads. GNOME and other
> >>>> DE's provide hooks to disable the touchpad altogether - suspending it
> >>>> achieves that.
> >>>
> >>>> Now, there are some issues that we should discuss:
> >>>> * the touchpad use-case seems to be mainly caused by bad palm detection in
> >>>>   the synaptics driver. Presumably having near-perfect palm detection
> >>>>   would remove the need for that toggle (except on the
> >>>>   devices that have that magic "disable touchpad button" on the touchpad
> >>>>   itself). So there's an argument that we don't necessarily need this, but I
> >>>>   don't know yet how good palm detection can be.
> >>>>
> >>>> * the second problem: I don't think we provide enough information to
> >>>>   callers to identify which device we don't need. Short of name matching
> >>>>   there is no way currently to a touchpad before disabling it. Same goes for
> >>>>   identifying any other device we don't care about.
> >>>>   To allow that, we'd need some sort of device identification system beyond
> >>>>   simple capabilities.
> >>>
> >>> [...]
> >>>
> >>> I think the suspend/resume approach is not the right one, at least not in
> >>> this form. A better option is to make this a config setting on the device,
> >>> specifically something like:
> >>>
> >>> libinput_device_config_set_disabled_mode(device, <which>)
> >>> with the parameter being one of:
> >>> - ...ENABLED
> >>> - ...DISABLED
> >>> - ...TOUCHPAD_SMART_DISABLE
> >>>
> >>> ENABLED is what it is, DISABLED still leaves the top button enabled, routed
> >>> through the trackstick where applicable.
> >>>
> >>> SMART_DISABLE solves the above use-case nicely. Identifying which device has
> >>> that feature becomes relatively simple (is the flag set in
> >>> libinput_device_config_get_disabled_modes()?) and what exactly is the
> >>> SMART_DISABLE is left to the implementation. The default would be to disable
> >>> when an external mouse is connected, otherwise leave enabled.
> >>>
> >>> Finally, from a semantic point of view, having this as configuration is more
> >>> logical as we expect this to be pretty much set once and done with it.
> >>
> >> SMART_DISABLE. As a potential consumer of the API, I find it too vague.
> >> I wouldn't know what's smart about it, and what use cases it would
> >> enable. See below.
> > 
> > just fyi, this was changed in the most recent patchset, providing 
> > ENABLED/DISABLED/DISABLED_ON_EXTERNAL_MOUSE at the moment
> > http://lists.freedesktop.org/archives/wayland-devel/2014-September/017042.html
> > 
> >>
> >> As for the possible use cases for disabling the touchpad:
> >> - The hardware's broken (yeah, that happens) or so awful that you don't
> >> want to ever see it. I just disable it and use an external mouse.
> > 
> > I think this would be something better solved by a udev option that libinput
> > reads. Broken hardware is a permanent option and doesn't need to be modified
> > in the session.
> 
> Brokenness is a relative thing here, one user may consider some cheaper touchpads
> broken / unusable others may not. If it really really is broken at a fundamental
> level, we should actually have the kernel not expose an evdev device for it. If the
> kernel does expose an evdev device for it, then I would expect it to work at least
> to some extent.

sure, but it still results in: user decides once that HW is broken, disables
it permanently. Which is the use-case we need to worry about most, if it's
so broken the kernel doesn't expose an evdev device we can ignore that case
within libinput anyway.

Cheers,
   Peter


> >> - Partial disabling, disable touchpad when using trackpoint:
> >>   https://bugzilla.gnome.org/show_bug.cgi?id=658980
> > 
> > I've got some general ideas on how to improve that, I'm not sure yet whether
> > a separate option here is necessary. That bug wants palm detection, and if
> > we have a "touchpad disabled" option anyway, a separate option of "disable
> > while I'm using the trackpoint" shouldn't be needed.
> 
> Some users tend to witch between workflows depending on if their coding /
> browsing the web / etc. For those "disable while I'm using the trackpoint"
> may make sense. I agree that it would be better to just get our palm detection
> code good enough though, and that that is where we should focus on.
> 
> >> - Partial disabling, disable trackpoint altogether:
> >>   https://bugzilla.gnome.org/show_bug.cgi?id=617932
> > 
> > commented on that bug, not sure why this is needed. trackpoints are not
> > known for their erratic events.
> 
> Ack.
> 
> >> - Disabling touchpad when in tablet mode. For Lenovo Twists, Yoga, 
> >>   X201T, etc.:
> >>   https://bugzilla.gnome.org/show_bug.cgi?id=698226
> > 
> > if the kernel gives us the event, we can make this happen automatically.
> 
> Ack.
> 
> Regards,
> 
> Hans