[OE-core] [PATCH 2/2] udev: enable multilib support

[Richard Purdie]

On Fri, 2013-04-05 at 16:29 +0300, Alex Damian wrote:
> On udev-184 they changed the default location from /sbin/
> to /lib/udev/ and I kept same as the upstream is.

Firstly, I know some people did ask me questions offlist about this and
I probably gave misleading answers. I thought this was a problem with
the location of the rules directory initially. We need to have one rules
directory regardless of multilibs.

Binaries however are a very different question. The multilib code we
have in OE is complex and does make some assumptions about layout, not
least as we have to interface into several package managers and also
work with all their assumptions. The situation is that:

* library files are expected to go into /libX
* binaries are expected to go into the usual bin/sbin dirs
* files in /etc, /usr/share and other similar directories are expected 
  to be identical
* We have sanity tests which check for these things

The package managers are taught to let certain packages "win" in
bin/sbin and to error if overlapping files outside this are not
identical.

It therefore follows that we would have to start adding exceptions to
this code if we have potential for both 32 bit and 64 bit /lib/udev/
binaries. We'd also have to add rules about which one would be expected
to "win" under which circumstances and so on.

To me, the simplest solution here is to point libexec dir at /sbin so
that we have /sbin/udev/ since this then works with the various multilib
rules. It means a user can install the 64 bit and 32 bit multilibs for
udev in parallel (for libudev for example) and that things should all
work correctly.

I appreciate upstream don't agree with that approach but equally they
don't have the generic multilib support we have to worry about. Hacking
the multilib code to pieces just to match upstream in this case is going
to be a lot more painful, I appreciate its the not optimal solution
though.

There is some pressure here since I would like the release to have
working multilib support as well as sysvinit and systemd :/.

Cheers,

Richard