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Re: debian and UDEV

Marco d'Itri wrote on 15/05/2006 14:03:
> brederlo@informatik.uni-tuebingen.de wrote:
>>You can't wait for an hotplug/udev event to be done processing. That
>>is always done asynchron without any feedback of completion.
> This is not correct. Look at the while loop in the init script and and
> the udevsettle source.

Which init script? And udevsettle? I don't see any such tool, manpage or
package in Debian, let alone some source for it that I could find.

>>will randomly fail or succeed depending on current scheduling. Any
>>sequence of loading a module and using the expected device node has to
>>utilize a sleep statement and prey udev runs fast enough to complete
>>in the given time.
> Wrong.

While your comments might be right [1], udev is pretty difficult for
admins to complete grasp and configure in the way they want it, let
alone "simple users".
With static device nodes (or devfs for that matter), "insmod <driver>;
mount <expected_device> <mountpoint>" always works. With udev, I had
that fail a number of times, unreproducible, since to reproduce it, I
tried to do it manually. Of course udev is faster than I am, so doing
those commands in sequence manually always worked.

Also, when doing "insmod <usb-storage-1>; insmod <usb-storage-2>" (where
usb-storage-[12] are two drivers for different usb storage devices), you
are not guaranteed that the first one actually get's the lower device
numbers. Of course, numbered devices (/dev/sda, '/dev/sdb etc.) are not
really what was in udev's initiators' minds, but it is still usefull to
always find the first SCSI/USB/SATA disc in a system at /dev/sda.


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