Is there any performance difference between udev and evdev in xorg?

[Aryeh Friedman]

Sorry to top post but there seems to be a message missing in the thread

On Wed, Sep 16, 2020 at 3:37 AM Alexey Dokuchaev <danfe at freebsd.org> wrote:

> On Wed, Sep 16, 2020 at 08:41:28AM +0200, Niclas Zeising wrote:
> > On 2020-09-16 06:01, Alexey Dokuchaev wrote:
> > > On Tue, Sep 15, 2020 at 10:55:31PM -0400, Aryeh Friedman wrote:
> > >> What if any is the performance difference between udev and evdev when
> > >> configuring xorg?  Also do I need to use one or the other consistently
> > >> or can I intermix them?
> > >
> > > If you don't need them (e.g. because this is desktop system without
> > > fancy input devices), you'd better off with disabling both of them
> > > altogether and use good old traditional way, that is, simply install
> > > xf86-input-{keyboard,mouse} and let X.org handle those peripherals.
> > >
> > > Yes, you would still be able to plug and unplug your USB mice and
> > > they will be detected and working as expected.
> > >
> > > TL;DR: DEVD/UDEV support is overrated and usually not needed at all.
> >
> > This is bad advice.
>
> OK, let's see why is it bad. :-)
>
> > The DEVD support in xorg-server might go away, since it is a FreeBSD
> > only solution and the udev/evdev is similar to what is used on Linux.
>
> Does this imply that DEVD support in X.org is technically inferior to
> udev/evdev, or it might get deprecated just because they prefer Linux
> way, regardless of the actual design and implementation quality?  Kind
> of tangentially related question, but this might help to foresee what
> to expect from future X.org development.
>
> > If you are using Wayland, it is also the only way to use input devices.
>
> Wayland is overrated and unneeded as well.  Plus, we're discussing X11
> here and X.org server in particular, how's that even relevant?
>
> > If you are using the default configuration of xorg on FreeBSD 12.1 or
> > later, using udev is the default.  This means using xf86-input-libinput
> > as the input device driver in X, and not xf86-input-{keyboard,mouse}.
> > This gives much better support for things like synaptics touchpads and
> > similar devices.
>
> Like I've said initially, these might come handy, but for "desktop system
> without fancy input devices", what's the point of bringing another layer
> of abstraction (xf86-input-libinput) rather then let X.org talk to device
> drivers drivers directly and not having to deal with evdev/libinput bugs,
> tinker with sysctls (kern.evdev.rcpt_mask), etc.?
>
> > You can configure such devices either by adding X configuration snippets
> > to /usr/local/etc/X11/xorg.conf.d/ or by using xinput on the command line
>
> Right, and with the old way, device configuration snippets are not needed.
> Just that simple.  So, the advice does not look that bad after all. :-)
>
> TL;DR: if there's a simpler solution/approach which is sufficient for one's
> needs, e.g. for simple three-button mouse and pc104 keyboard, just dump the
> extra xf86-input-libinput bloat and stick to old, well-tested, solid code
> which just works(tm).
>
> ./danfe
>


-- 
Aryeh M. Friedman, Lead Developer, http://www.PetiteCloud.org