udev PROGRAM key and the device chain walk

[Kay Sievers <kay.sievers@vrfy.org>]

While we try to match rule keys against a devices sysfs representaion,
we need to follow the physical device and walk up the device chain up to
the root device and match our rule against every device found.

While this is necessary to match the SYSFS and BUS keys, it has the
_very_ bad side effect, that a PROGRAM may be executed several times. In
my test setup, I've seen five executions of a callout to match one single
rule.

The only reason to do this, is the match with a callout against a sysfs
attribute of one of the physical devices along the chain by using
the %s{<attr>} key.
I don't think that this is really needed and I want to change the namedev
logic to execute the PROGRAM key only once per rule. It will be still
possible to pass the %s{<attr>} to the callout, but it will only happen
at the device itself and not follow the chain to the root device. If
such a thing is ever needed, the callout can do it itself and not rely on
udev to execute it several times.

Any objections, or I will change that to speed things up.

Thanks,
Kay


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