On Tue, Nov 30, 2004 at 09:17:26PM -0500, Edwin Olson wrote:
> At the risk of beating a dead horse...
> 
> >You can work backwards from a /dev node to the sysfs /class path using
> >udevinfo:
> >     udevinfo -n /dev/tts/USB0 -q all
> >     P: /class/tty/ttyUSB0
> >     N: tts/USB0
> >     S: 
> >
> >From the "P:" line above, you can follow the "device" symlink in that
> >directory to get to the directory that you need, right?
> > 
> >
> Will udev *always* return a /class path, or might it sometimes return a 
> /device path or a /bus path? Is this behavior defined?

P: will always return the location in the sysfs tree for the device that
created the node.  Only devices in /sys/block/* or /sys/class/* provide
information to userspace to create device nodes.  Symlinks in those
sysfs directories, then point back to a location in the /sys/device/
directory, for which there will also be other symlinks to the /sys/bus/
directories.

Just remember, sysfs is, "A web woven by a spider on drugs"[1] and
everything will become more clear :)

thanks,

greg k-h

[1] a quote from lwn.net that I can't find at this moment, sorry.


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