Re: udev doesn't know about devices further up the tree.

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

On Fri, 2006-06-16 at 09:50 +0100, Simon Huggins wrote:
> On Fri, Jun 16, 2006 at 10:35:33AM +0200, Kay Sievers wrote:
> > On Fri, 2006-06-16 at 09:05 +0100, Simon Huggins wrote:
> > > I wrote my first udev rule the other day.
> > > It reads:
> > > KERNEL="sd*", PROGRAM="/home/huggie/bin/camera %k", SYMLINK+="%c"
> > > where bin/camera does:
> > > DEV=$1
> > > DISK=`echo $DEV|sed -e 's/.*\(sd.\).*/\1/;'`
> > > udevinfo -a -p /block/$DISK/$DEV|grep manuf|grep PENTAX >/dev/null 2>&1 && \
> > >         echo camera && exit 0
> > > i.e. basically if the usb device (or any device because I'm not that
> > > fussy) above the block device is made by PENTAX then echo camera
> > > otherwise I just echo $DEV back again.
> > > But it strikes me as a bug that I have to spawn out of udevd to run
> > > udevinfo in order to just name the device based on what it is.
> > > Why aren't SYSFS attributes from higher up the device path available
> > > somehow when writing rules?
> > Adding a single SYSFS attribute:
> >   SYSFS{vendor}="PENTAX"
> > or
> >   SYSFS{manufacturer}="PENTAX"
> 
> > should do it and will try to find the value on all devices up the chain,
> > but you can't mix SYSFS, BUS or ID values from different devices.
> 
> Hmm, ok it's working now.  I must have fucked up the rule somehow
> originally sorry for wasting your time.
> 
> Can I suggest that the part in
> http://www.reactivated.net/writing_udev_rules.html
> which says:
> 
> 	This is to demonstrate that you generally can not mix-and-match
> 	attributes from different sections of the udevinfo output - your
> 	rule will not work. 
> 
> be reworded or removed then.  I'm not quite sure what it should say - I
> just failed and then read more of the docs and came across this and
> thought that what I was trying was never going to work.
> 
> I now have:
> KERNEL="sd*", SUBSYSTEM="block", SYSFS{manufacturer}="PENTAX",
> SYMLINK+="camera"
> which appears to work fine yet the block and the PENTAX are indeed in
> different sections of the udevinfo output.

Right, I means, you can't mix attributes of different parent devices.
The attributes for the device itself, which "block" belongs to, will
always match. Say:
  SYSFS{vendor}="PENTAX", SYSFS{manufacturer}="PENTAX"
would not match, even when both single keys are matching.

Kay



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