Re: hotplugging on an embedded system under 2.6.17(-rcX)

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

On Wed, 2006-06-07 at 14:08 +0200, Guennadi Liakhovetski wrote:
> On Wed, 7 Jun 2006, Kay Sievers wrote:
> 
> > On Wed, 2006-06-07 at 12:06 +0200, Guennadi Liakhovetski wrote:
> >>
> >> That's approximately what I've done now - disabled the default mounting of
> >> tmpfs on the top of /dev
> >
> > But you are not using /dev from flash, right?
> 
> Emn, which flash? It's not NOR-flash in this case, it's on CF... In other 
> setups we do have /dev in NOR-flash. Is it bad? We even did ext2 rw in NOR 
> as /dev - rw because you have to be able to "write" to it, ext2 because it 
> will anyway not be written TO the flash. Now with udev creating new nodes
> dynamically we wouldn't do that of course.

Well, I would always use a tmpfs filesystem on /dev, so you always start
with a well defined setup. As long as we don't have a unionfs we can
overlay over /dev, it's the safest to copy your few initial device nodes
to tmpfs and let udev mess around with it from that point. Udev also
stores temporary files in /dev/.udev may be a bit faster on tmpfs.

> >> and "synthesizing" nodes, left the static initial
> >> device nodes alone, disabled /proc/sys/kernel/hotplug, started udev to let
> >> it handle further hotplug events - seems to work quite good so far! I'll
> >> test benchmark it further, but so far it looks really good!
> >
> > Sounds good.
> 
> Yeah... Only I cannot repeat it... I mean, I have one experimantal system, 
> where it works. And another "clean" system (near to the final 
> configuration) where I cannot get it to work - I cannot get udevd to load 
> modules there... under /dev/.udev/failed I get:

You have the RUN+="/sbin/modprobe $env{MODALIAS}" rules like this,
right?
  http://www.kernel.org/git/?p=linux/hotplug/udev.git;a=blob;hb=HEAD;f=etc/udev/debian/hotplug.rules

Kay



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