On Fri, Sep 04, 2009 at 12:59:10AM -0400, Felipe Sateler wrote:
> >>> The issue was raised by the udev upstream maintainer along with the udev
> >>> package maintainers of the major distributions, who all agreed that this
> >>> configuration is not supported.
> >> FYI, udev 146 ships usb-id and pci-id programs which read
> >> /usr/share/misc/usb.ids and /usr/share/misc/pci.ids .
> >> udev itself does not care about the results of these programs but other
> >> programs which used to use HAL may do, leading to subtle breakage.
> > Reading again your mail, I think we are discussing a inexistent problem.
> > You say that "some programs which use HAL may do" use /usr/share.
> Hal also lives on /usr, so I don't see the problem either.
The problem is this:
- In udev 146 and above, a number of the stock udev rules call the
/lib/udev/{pci,usb}-db helpers to query the vendor name / product name
and and this information to the udev environment.
- These helpers work by parsing the pci.ids and usb.ids databases, which
have long had standard locations that are *not* in /lib (either in /usr
or in /var, both of which are allowed to be separate filesystems under
the FHS).
- Now that there are udev rules exporting this information, arbitrary other
components in the stack may come to rely on this information being
available (but we don't seem to know what components; the rationale for
this facility being added to udev so far is pretty opaque, though
whatever it is can't be good).
- These udev rules are applied from runlevel S, before /usr or /var are
guaranteed to be mounted. That means that any device which is detected
by the kernel before this point (such as non-hotpluggable PCI devices)
will have different information exported by udev depending on whether
/usr and /var are on the root filesystem.
I still can't fathom why someone decided that udev should be responsible for
translating PCI IDs and USB IDs into text strings. This smells of crazy.
--
Steve Langasek Give me a lever long enough and a Free OS
Debian Developer to set it on, and I can move the world.
Ubuntu Developer http://www.debian.org/
slangasek@ubuntu.com vorlon@debian.org
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