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

[Niclas Zeising]

On 2020-09-16 10:07, Grzegorz Junka wrote:
> 
> On 16/09/2020 07:37, Alexey Dokuchaev 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.
>>
> 
> Linux way doesn't mean it's a bad way. As a user I don't really care if 
> it's Linux way or not as long as it supports the hardware that I spent 
> my money on.
> 
> As a developer I do care about a solution that is simpler to code and 
> use, but not if it's Linux or not. Can you actually define what you mean 
> by Linux way?
> 
> However, the most important thing that I care about is that the code I 
> am learning and using is copyfree. If someone was kind enough to rewrite 
> the whole Linux using a FreeBSD license then I wouldn't mind switching 
> to do that to make a better use of the hardware that I have.

In this case, it is copyfree.  We have a udev/evdev compat layer in the 
FreeBSD kernel that is BSD licensed, since it was developed on and for 
FreeBSD.  For the rest of the stack, which means libinput and the device 
handling in X and wayland, it is MIT licensed, since upstream code 
generally is MIT licensed.
Regards
-- 
Niclas Zeising