Gentoo Archives: gentoo-user

From: Alan McKinnon <alan.mckinnon@×××××.com>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] no keyboard no mouse
Date: Sat, 25 Jun 2011 19:17:28
Message-Id: 5189594.mBGS0zCxMF@nazgul
In Reply to: Re: [gentoo-user] no keyboard no mouse by Alan Mackenzie
1 On Saturday 25 June 2011 09:50:15 Alan Mackenzie did opine thusly:
2 > Hi, Alan.
3 >
4 > On Fri, Jun 24, 2011 at 04:57:05PM +0200, Alan McKinnon wrote:
5 > > > Hmm. Recompiling the same source code produces a different
6 > > > binary?
7 > >
8 > > Not quite:
9 > >
10 > > Rebuilding the same sources against different headers produces a
11 > > different binary.
12 > >
13 > > > Presumably, it uses C macros in a .h file which is part of
14 > > > xorg. Or something like that.
15 > > >
16 > > > So evdev depends on xorg. Isn't there a way of expressing
17 > > > this in evdev's ebuild? Something like the DEPEND
18 > > > variable?
19 > >
20 > > It's already there, but doesn't help as the update trigger never
21 > > happens.
22 > >
23 > > Actually, you have the depend the wrong way round - evdev
24 > > depends on xorg-server; to have the driver and for it to be
25 > > useful, the xorg- server must be present, otherwise there is
26 > > nothing for the drivers to build against.
27 > >
28 > > You want to force a rebuild that is the opposite of the DEPEND,
29 > > but portage does not support that (it's a circular dependency).
30 > > It will also not rebuild the driver as part of a regular update
31 > > as there is not a new version of the driver, hence according to
32 > > normal portage logic there is no need to do so.
33 > >
34 > > Make sense?
35 >
36 > I think so - I've always had problems understanding dependencies.
37 > What I want is one of these "nice to have"s which would take an
38 > inordinate amount of work, if it's even possible.
39
40 Trouble with dependencies is they present themselves the wrong way
41 round when you try to debug them. It's the classic grandfather
42 problem:
43
44 I ask you "who is your granddad?", that's an easy one, you say it's
45 John Smith. Now I go find John Smith and ask him "who's your
46 grandson?" He says "I have more than one. Which one you interested
47 in?" and you can't answer that without more information.
48
49 When you look in an ebuild for DEPENDS, you are using the first case.
50 When you try debug portage output, you often end up at the second
51 case.
52
53 I imagine the real reason portage doesn't have excellent tools to help
54 answer that is becuase the problem is infernally difficult to do
55 correctly, and the output will always be mind-bogglingly confusing.
56
57 Moving a little off-topic, I have a similar thing at work. A perfectly
58 valid question I often get asked is "when did we last receive a mail
59 to xyz@×××××××.com?" HR want to know this so they can know when to
60 retire an address. I can't tell them, not without an exhaustive manual
61 search of mail logs.
62
63 > In the meantime, I'll carry on not starting Gnome at boot-up.
64 > Despite the existence of gentoo=nox, I feel safer starting it
65 > manually. It's a strange, depressing feeling when the only input
66 > device which works is the reset button - thank goodness that isn't
67 > handled by evdev. ;-)
68
69 Yup, loss of input devices in the most annoying pain in the arse
70 imagineable. Remember when xorg was a huge monolithic code base and
71 you always got everything every time, but the dependency issues just
72 simply never happened?
73
74
75 --
76 alan dot mckinnon at gmail dot com