Message-ID: <20170530145618.081c1511@kitsune.suse.cz>
Date:   Tue, 30 May 2017 14:56:18 +0200
From:   Michal Suchánek <msuchanek@...e.de>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        Peter Hutterer <peter.hutterer@...-t.net>
Subject: Re: [PATCH] macintosh: move mac_hid driver to input/mouse.

On Tue, 30 May 2017 14:02:55 +0200
Benjamin Tissoires <benjamin.tissoires@...hat.com> wrote:

> On May 30 2017 or thereabouts, Michal Suchánek wrote:
> > On Tue, 30 May 2017 12:33:21 +0200
> > Benjamin Tissoires <benjamin.tissoires@...hat.com> wrote:
> >   
> > > Hi Michal,
> > > 
> > > On May 30 2017 or thereabouts, Michal Suchánek wrote:  
> > > > On Mon, 29 May 2017 22:06:06 -0700
> > > > Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> > > >     
> > > > > On Mon, May 29, 2017 at 08:03:25PM +0200, Michal Suchánek
> > > > > wrote:    
> > > > > > On Sun, 28 May 2017 10:55:40 -0700
> > > > > > Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> > > > > >       
> > > > > > > On Sun, May 28, 2017 at 11:47:58AM +0200, Michal Suchanek
> > > > > > > wrote:      
> >   
> > > >     
> > > > >     
> > > > > > 
> > > > > > More importantly how is that mapping supposed to be
> > > > > > represented in a hwdb file?
> > > > > > 
> > > > > > The help text in the hwdb file says:
> > > > > > 
> > > > > > # Scan codes are specified as:
> > > > > > #   KEYBOARD_KEY_<hex scan code>=<key code identifier>
> > > > > > # The scan code should be expressed in hex lowercase. The
> > > > > > key codes # are retrieved and normalized from the kernel
> > > > > > input API header.
> > > > > > 
> > > > > > So they are converted in some unspecified way.
> > > > > > 
> > > > > > The example below defines some mappings, presumably:
> > > > > > 
> > > > > > evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn*
> > > > > > evdev:atkbd:dmi:bvn*:bvr*:bd*:svnGateway*:pnA0A1*:pvr*
> > > > > > evdev:atkbd:dmi:bvn*:bvr*:bd*:svneMachines:pneMachines*E725:pvr*
> > > > > >  KEYBOARD_KEY_a5=help                                   #
> > > > > > Fn+F1
> > > > > > KEYBOARD_KEY_a6=setup                                  #
> > > > > > Fn+F2
> > > > > > KEYBOARD_KEY_a7=battery                                #
> > > > > > Fn+F3
> > > > > > 
> > > > > > /usr/include/linux/input-event-codes.h has occurence of
> > > > > > battery in
> > > > > > 
> > > > > > #define KEY_BATTERY		236
> > > > > > 
> > > > > > meaning that the unspecified conversion is probably
> > > > > > performed by
> > > > > > 
> > > > > > 1) stripping KEY_ prefix
> > > > > > 2) converting to lowercase
> > > > > > 
> > > > > > This is what systemd hwdb check script does in reverse when
> > > > > > checking the keycode values.
> > > > > > 
> > > > > > The BTN_LEFT 0x110 value does not conflict with KEY_*
> > > > > > values, though. So technically you could include it in the
> > > > > > keymap. If you had a tool for that.      
> > > > > 
> > > > > Hmm, sounds like you want a patch to udev/systemd. For the
> > > > > kernel there is no difference between keys and buttons,
> > > > > except symbolic names. They all go into dev->keybit and are
> > > > > reported with input_report_key().    
> > > > 
> > > > So the userspace is not ready for this while the kernel already
> > > > has the driver for ages and all that is needed is to enable
> > > > it.    
> > > 
> > > The problem is more that you can have your particular issue solved
> > > here by using this particular driver. But then someone says that
> > > the mapping for right/middle doesn't fit to his/her keyboard
> > > layout, and then we will have to maintain an new set of fancy new
> > > features in a driver that is just legacy.  
> > 
> > The mapping is dynamic. You specify which keycode you translate to
> > which button by writing a sysfs file and if you do not nothing is
> > translated. So far as plain mouse emulation goes this driver is
> > perfectly fine. It will probably not emulate a scrollwheel and other
> > fancy features but that can be solved in later more flexible
> > solution once it is finished. And once it is finished then is the
> > time for retiring this driver.  
> 
> My bad. Still, it doesn't change the fact that this driver should be
> pointless and retired, because it has to be done in userspace.
> 
> >   
> > > 
> > > 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.
> > > > 
> > > > 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.
> 
> >   
> > > 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  
> 
> 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.

> 
> >   
> > >   
> > > >     
> > > > > 
> > > > > 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.

> 
> 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?
> >   
> 
> But is this a reason to stop proposing patches to those projects or
> report bugs?

The bugs are reported. I do not have a patch proposal to fix nouveau
locking so it does not trip over itself all the time nor a workaround
for ATOMBIOS bugs that crash the graphics under some less common
circumstances which unfortunately still happen and make affected system
unusable .. unless you are _very_ careful not to trigger them.

> We already told you the kernel is not the place. The kernel can do a
> lot, true, but when the input maintainer tell you this is not the
> place, you should have a pretty good hint that it is not the place.

And it has been clearly determined that if anything the place is
systemd using the in-kernel mapping. However, systemd does not have the
functionality while the mac mouse emulation does.

> 
> > >   
> > > >     
> > > > > 
> > > > > Solving this at kernel is wrong place, similarly how we avoid
> > > > > parsing user gestures (edge scrolling, 2-finger scrolling,
> > > > > pitch/zoom, etc) in kernel. Yes, we have legacy drivers (like
> > > > > mousedev) that are artefacts of times when userspace support
> > > > > was not there and it made sense to covert everything to
> > > > > emulated PS/2, but that time is long gone.    
> > > > 
> > > > Unlike 2-finger scrolling, pitch/zoom, and whatnot key mapping
> > > > is something kernel can do, does, and should do.    
> > > 
> > > Looks like we are all on the same page. Kernel does key mapping
> > > already and doesn't do 2-finger scrolling and other gestures.
> > > 
> > > The difference in approach is that you want the kernel to emulate
> > > devices when userspace has much more information to know how to
> > > emulate those devices.  
> > 
> > Any piece of software has the information when the user tells it.
> > The thing is the kernel is also able to emulate the device and the
> > userspace is not. And seriously, this is a hardware problem which is
> > simple to solve once for good in kernel. Do you advocate that
> > instead  
> 
> It is a hardware problem that is not solvable in the kernel (or should
> not). Would the keyboard had specific keys designed to send buttons,
> yes, we would have do our best. But here you are trying to counter a
> hardware design issue by using a hack at the wrong level. That's all
> we are saying.

And if the vendor put a LMB and RMB stickers on some keyboard keys then
it would be fine? I mean then it would be designed to send mouse
buttons even if it sends key events in practice, right :>

Then I can fix it and put a sticker on the key myself :>

> 
> > everyone should set up mouse emulation in N application frameworks
> > and implement it in those that miss it?  
> 
> Well, given the amount of people involved in the input community, you
> can be sure that adding this in libinput is just enough.
> 
> >   
> > > 
> > > The kernel job is to forward events from the devices to userspace
> > > without losing information and in a standard way. Anything beyond
> > > that should be handled in userspace.  
> >  
> > Then why do you do keycode translation at all?   
> 
> Because keycode translations are used for fixing hardware when the
> keycode sent is non standard, and instead of requiring people to send
> kernel patches for it, it's better to ask them to drop a hwdb entry
> for them. This doesn't contradict what I said: it helps forwarding a
> random event from the device into a standard one.
> 
> keycode translation also helps setting layouts on TTY. Because when
> you are on a TTY there is not much you can do in userspace to fix it.

So the kernel *is* responsible for translating the keys to whatever the
user sets up. Because it is the only place possible to make it work for
all applications.

> 
> > I guess because it is the job of the kernel to make the information
> > usable by the applications as well.  
> 
> Yes and no. The kernel forwards the information in a standard way to
> applications. If you want to locally remap any key to any other event,
> fine. But it shouldn't be the default.

And I do not propose for it to be the default. I just want that the
driver to send the different key not be arch-dependent. So you can
build it on any arch if you want to use it. You still have to configure
it to do the translation on your particular system because by default
it does nothing.

> 
> >   
> > >   
> > > > 
> > > > The difference between the plain mapping and mac mouse
> > > > emulation is that mac mouse emulation probably creates a
> > > > separate pointer device which is as compatible with legacy
> > > > software as it gets. Unlike application-specific solutions it
> > > > works in any software that accepts input events including X.
> > > > And unlike the systemd solution it works today.    
> > > 
> > > And we can argue that the issue with the mac mouse emulation is
> > > that it filters on all connected keyboard.
> > > Meaning that if you connect an external keyboard just from time to
> > > time, those two keys will send the emulated buttons instead of
> > > sending plain key events.  
> > 
> > Well, that's a limitation of simple solution. 
> >   
> > > 
> > > While on a libinput approach, the filtering will only affect the
> > > internal keyboard, making the whole experience better.  
> > 
> > Unless it happens to crash the X server.  
> 
> How can you know it'll crash the X server when the feature is not even
> implemented?

It may not, of course.

> 
> Luckily, Peter is also in charge of XInput, so I guess if it crashes
> the server, it will be detected/fixed way before it is public.

Sadly, such bugs escaped more than once and were only found by users
because the mappings which send key presses on a mouse or mouse button
presses on a keyboard are uncommon and not well tested.

> 
> >   
> > >   
> > > > 
> > > > Given the state of userspace at this point I find using the mac
> > > > mouse emulation most sensible thing to do. Improving the keymap
> > > > support in systemd is certainly more flexible so it is the way
> > > > to go long term but if a patch is written and accepted today it
> > > > will take years until support is commonplace. On the other
> > > > hand, the change required in Linux is trivial and updating the
> > > > kernel without breaking the whole system is much more viable
> > > > than updating systemd.    
> > > 
> > > With a libinput approach, the time to distro is much reduced
> > > (unless you are running a *very* old libinput release that is not
> > > ABI compatible anymore).  
> > 
> > There is no libinput approach. They eschew mapping since there is
> > one in systemd and one in X already.   
> 
> Please see above. Open a bug and we can start talking.
> 
> >   
> > > 
> > > And we can return the argument for the kernel. The time for a new
> > > option in the kernel to land in some distribution can also be
> > > counted in years.
> > >   
> > 
> > Indeed. However, running own kernel is much more likely to succeed
> > than running own systemd.  
> 
> And recompiling a local libinput is way faster than recompiling the
> kernel. I never talked about systemd, but libinput.

But you newer showed how implementing a feature in libinput fixes the
problem either.

Thanks

Michal

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