Date:   Wed, 7 Jun 2017 14:29:30 +0200
From:   Michal Suchánek <msuchanek@...e.de>
To:     Peter Hutterer <peter.hutterer@...-t.net>
Cc:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH] macintosh: move mac_hid driver to input/mouse.

On Wed, 31 May 2017 14:26:52 +1000
Peter Hutterer <peter.hutterer@...-t.net> wrote:

> On Tue, May 30, 2017 at 02:56:18PM +0200, Michal Suchánek wrote:
> > > > > I concede userspace doesn't have the feature, but you should
> > > > > really have a look at libinput (i.e. open a bug on
> > > > > bugs.freedesktop.org) and request the feature here.
> > > > >     
> > > > > >       
> > > > > > >       
> > > > > > > > And if it is not rejected by the kernel.        
> > > > > > > 
> > > > > > > It should not. setkeycodes definitely works on atkbd.
> > > > > > >       
> > > > > > > > And if it does not
> > > > > > > > crash your X server which is very picky about receiving
> > > > > > > > pointer events from a keyboard or the other way
> > > > > > > > around.        
> > > > > > > 
> > > > > > > Sounds like you want to make X server more
> > > > > > > resilient ;)      
> > > > > > 
> > > > > > This is an inherent design flaw in the X server known for
> > > > > > years. It has separate keyboard and pointer devices and
> > > > > > while people are trying to patch it up occasionally a bug
> > > > > > pops out that crashes the Xserver when an event is received
> > > > > > from non-matching device type.  
> 
> fwiw, the pointer/keyboard split problem was fixed in
> xf86-input-libinput with 1f43f3921f6c in late 2015. it's possible to
> fix it in the same manner for the evdev driver, but someone would
> have to be very motivated.

That is a good news. A problem considered unsurmountable for years is
finally overcome.

> 
> > > > > > 
> > > > > > Once X server dies and is replaced be Y server or Z server
> > > > > > or whatever it will make life easier in so many ways.      
> > > > > 
> > > > > We already have libinput that tends to replace the Xorg input
> > > > > part (at least everything which is not protocol).     
> > > > 
> > > > And the protocol still has the split to pointer and keyboard.
> > > > It is technically possible to map mouse button presses with XKB
> > > > but it only works in X and is undocumented and really difficult
> > > > to do. And it does not work outside of X.    
> > > 
> > > I never talked about XKB. Libinput has a view on all input
> > > devices and can redirect whatever events it sees into any other
> > > input device. From a X perspective it's as if the emulated button
> > > would have been generated by the touchpad itself.

As much as when it is generated by XKB. It is just different layer
inside the X server.

> > >   
> > > >     
> > > > > So if the feature is in
> > > > > libinput, it should be available in X.org directly, and you
> > > > > will be saved.    
> > > > 
> > > > Not everything uses libinput. So no, using libinput is not the
> > > > answer.    
> > > 
> > > If you do not want to upgrade and use the latest development
> > > tools, then sure, you can always use the mac_hid emulation. But
> > > we will not resurrect it because it's something from the past.
> > >   
> > > > 
> > > > Also libinput people suggest to use hwdb for mapping which is
> > > > back to where we were:
> > > > https://lists.freedesktop.org/archives/wayland-devel/2015-December/026223.html    
> 
> Note: in this thread I specifically say that remapping for *broken*
> keys should go in the hwdb, anything else needs to go into userspace.

These keys are either broken by design or worn down. 
The touchpad contains switches under the touch surface and you press
keys by pressing the touch area and tilting it to one side making it
impossible to press both buttons at once. Or on touchpads that have
separate physical buttons the left button tends to get more use
and wears much faster resulting in different force required to trigger
those two buttons. In either case it is not possible to trigger
gestures that require both buttons pressed simultaneously such as the
X11 middle button emulation so other mapping for mouse buttons is
required.

> 
> > > Libinput people are basically Peter Hutterer alone. And in the
> > > keyboard layout mapping, yes users should use hwdb/systemd for
> > > that. In your precise case, libinput should have a setting that
> > > redirect the incoming key onto a button of a different device.
> > > It's not implemented, it's doable, but you won't receive a NACK
> > > as you get here, because you have a valid use case for it.  
> > 
> > Libinput is not the place either. Libinput is a library for using
> > the input subsystem, not the input subsystem. So while it might be
> > advisable to use it when you can there will always be applications
> > that do not use it and those should receive correct input as well.  
> 
> I'm gonna chime in here and say that emulating button events from
> keys + mouse events is (probably) not something I'd merge into
> libinput anyway. I'd like to see the touchpads that are unable to
> even detect two fingers first. I haven't seen one of those released
> in 8 years and the ones that are left are probably at the end of
> their lifecycle. [However, you'll be happy to know that with libiput
> 1.7 and 1.6.2 we added clickfinger support for the apple onebutton
> touchpads. And that was only January this year. Both users have been
> partying non-stop since, I suspect.]

On the other hand, I would like to see a single touchpad that can
detect two fingers reliably. In absence of such I want to use
multitouch as little as possible relying on input technology not broken
by design - such as physical separate buttons.

> 
> Almost all touchpads these days are clickpads, i.e. they only have a
> single (left) button and anything else is software emulated. So
> anything that handles touchpads will have to deal with this before
> too long.

I don't know where you live. Where I live about half of the notebooks I
coming from decent vendors have touchpads with actual physical
buttons. Two of them. I can understand that fitting something like a
scrollwheel and making it work reliably is too much of an engineering
challenge for laptop makers. So it is fine to use multitouch feature
instead of a scrollwheel. It is not fine to use multitouch for features
that can be feasibly implemented reliably such as multiple mouse
buttons.

> 
> Spoiler alert: libinput was started not just because "Woo Wayland!"
> but because the Wayland compositor model requires each compositor to
> reimplement input handling. And handling input is hard, even if it
> doesn't look like it from a high vantage point. So having this in one
> central place, ready to be re-used is the way to go. Anything that
> doesn't want to use libinput is welcome to do so but you'll have to
> mix the ingredients yourself before you get to eat the cake.

Not everyone writes in C so it is not always easy to use libinput with
their code.

Regardless of that the kernel documentation says that /dev/event* is
the preferred interface to Linux input subsystem. Hence libinput is
only an optional convenience library and correct events should be seen
when read from /dev/event* using libinput or not. If correct for a
particular piece of hardware means that scancode 70065 sends BTN_RIGHT
then applications reading from /dev/event* directly including tools
like evtest should see the scancode and BTN_RIGHT.

> 
> > > > > > > But really, it all is better solved in userspace, where
> > > > > > > you can surface all options to the user. For example
> > > > > > > Chrome OS uses Alt + mouse button (or tap) to do right
> > > > > > > click, I am sure Gnome or KDE has similar support for
> > > > > > > right and middle buttons.      
> > > > > > 
> > > > > > I do not consider Gnome or KDE more suitable driver for my
> > > > > > keyboard than the Linux kernel. In fact I find both very
> > > > > > unsuitable as a driver, heavyweight, and causing problems
> > > > > > with graphical desktop usability. Not      
> > > > > 
> > > > > Well, with wayland, the compositor embeds the input stack and
> > > > > part of the graphic stack, and it's actually faster than
> > > > > X.    
> > > > 
> > > > That's pointless when it does not work as a desktop in practice.
> > > > 
> > > > And it does not make GNOME or KDE a suitable driver for
> > > > keyboard, even if you run Wayland.    
> > > 
> > > I am just not following what is your use case. Do you want to
> > > enable this feature in a TTY, in a full blown desktop, in a plain
> > > X that you launched with "/usr/bin/Xorg"?  
> > 
> > All of them. Why should my pointer behave differently depending on
> > the application I run? Is that the 'usability' you had in mind?
> > 
> > Yes, current X server and Wayland uses libinput so those are
> > covered. Hopefully I will never need to test anything with X server
> > so old that it does not have libinput based drivers but who knows.
> > 
> > However, not all is X and there are applications using gpm or
> > reading events directly or whatever which do not run under X.
> > Granted, I do not use them often but do I have to figure out why
> > the mouse is not working in those every time I try?
> > 
> > I want a solution that works as uniformly across all system as
> > possible.  
> 
> that puts you in a pickle. you want emulation of features not
> supported by the hardware to be pushed into the kernel. I face a
> similar request most days where users want features not supported by
> their toolkit or application to be pushed into libinput because it's
> easier. It's not always a good case, and often the answer is 'no'
> because long-term, it makes everything harder.

The hardware has buttons. Kernel does mapping of hardware buttons to
logical buttons for *every* hardware, anyway. I want it to map my
particular piece of hardware in a way that makes it usable. In every
application.

> 
> gpm *should* be able to handle this, and applications that read input
> directly should handle input. Because there are plenty of other
> features that have similar requirements. Have a look at consolation
> for example which uses libinput to be similar to gpm
> https://alioth.debian.org/projects/consolation/

I was more concerned about applications that used to use GPM for event
input. However, main purpose of GPM was to normalize different mouse
protocols to one event format which the kernel already does with evdev.
GPM protocol did not offer many different events so applications
talking to GPM (if any still remain) can be ported to evdev quite
easily I would expect. Porting to libinput might be a different story
altogether.

> 
> > > And if you just want Xorg with whatever desktop
> > > manager/environment, you should already be using libinput given
> > > that xorg-xf86-libinput is now the only maintained X driver for
> > > keyboards and touchpads. 
> > > >     
> > > > >     
> > > > > > to mention they cannot be used at all when not running a
> > > > > > graphical desktop and often cause system crashes due to
> > > > > > stressing the graphics hardware.      
> > > > > 
> > > > > If you experience crashes, they are probably bugs, and please
> > > > > report them to the appropriate project.    
> > > > 
> > > > And the answer is they know it crashes but it's too much work to
> > > > fix. Or that it works for them and you are just unlucky that
> > > > all of your half dozen cards crash with their driver and they
> > > > cannot do anything about it.
> > > > Maybe next year. Or the year after. Or with different piece of
> > > > hardware. Who knows?  
> 
> I don't know why you presume all these answers, but this is not a 
> good way to improve the discussion. 

I do not presume them. I have seen them as answers to bug reports which
I or other users of the hardware filed.

> We don't just exist to make your
> hardware work for free, any of us has more than enough work so we
> have to select what we work on. This should not come as a surprise.

And it should not come as a surprise that I do not want to use a piece
of software which is huge, gets in the way of using the desktop
environment, and potentially crashes my system due to reliance on
unfinished GPU drivers as a driver for my input device.

I can see it will take huge amount of work to make it stable, and
another huge amount of work to make it usable for me. So I do not
use it and rather want the system base to be fixed so the software that
works right now is usable with the hardware available and right now.

Thanks

Michal

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