Le 16/11/2017 à 10:25, Casper Ti. Vector a écrit :
On Wed, Nov 15, 2017 at 02:53:21PM +0000, Laurent Bercot wrote:
  Is it really the only place in Xorg that depends on libudev?
I'd think it would be much, much more entangled with libudev than
this.
Unfortunately, just as noted by Guillermo, libudev is also, in more
complicated ways, needed by quite a few x11 drivers and (perhaps most
importantly) xserver itself.  I apologise for (again) not thoroughly
investigating the issues before replying :(

  So, yeah. If you want a patch for xf86-input-evdev that will
make it stop depend on libudev, I can write one in an hour. But
that patch will likely never go upstream, because it goes against
policy; and complying with the policy would basically amount to
rewriting libudev and making a new udevd. Which I believe I'm quite
able to do, and better than the existing ones, but it would still be
bad software design, and I have no interest in contributing to the
problem.
(Again, I am not someone fluent in low level programming, so please feel
free to correct me if I make stupid mistakes in the following.)

 From my cursory glance at the x11 code that use libudev, and the libudev
documentation, the main functionalities of libudev seem to fall into two
almost orthogonal categories: those that abstract the sysfs interface,
and those that handle the udev event queue.  I have not come up with a
good idea on how to provide the latter in a vender-neutral way, but a
neutral design of the former seems obvious: if sysfs was really never
intended to be a stable interface at all, at least make a minimalist
library outside udev that provide the necessary functionalities.

However, as you noted, "sysfs has not changed interfaces to the point of
breaking stuff in 12 years and counting", so the intended instability is
not really an excuse; and even if we pretend that sysfs is so unstable,
stating that sysfs is "a private export only to be consumed by udev" [1]
(ie. not mdev, nldev, vdev, etc.) has no technical basis.  But noticing
that the actors in the drama include GKH and KS, this is unsurprising;
this is also the reason I refered to the conspiracy theory again.

[1] <https://landley.net/notes-2015.html#05-07-2015>

I agree that there is a conspiracy. The mails exchanged by Rob Landley are very explicit.

I don't think Linus Torvalds would tolerate on the long term that a group of people develop a private kernel interface for the purpose of forcing systemd to all Linux users. In fact I guess he is aware of this, and even sensitive to the bad quality of their code, but he will not move because only one person complains.

Rob Landley would have a stronger argument if a large number of users had their desktops running mdev and undocumented changes in sysfs breaks it.

    Didier


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