Re: udev rules for new firewire driver stack

[David Moore <dcm@MIT.EDU>]

On Wed, 2008-08-20 at 21:39 +0200, Stefan Richter wrote:

> # Set GROUP="video" for some IEEE 1394 device types, driven by the new firewire stack.
> # We cannot use the GROUP directive because the significant device type attributes
> # live in child devices. So change the group after the fact with chgrp.
> 
> # IIDC devices: industrial cameras and some webcams
> SUBSYSTEM="firewire", ATTR{specifier_id}="0x00a02d", ATTR{version}="0x00010?",\
>  PROGRAM="/bin/chgrp video /dev/%P"
> 
> # AV/C devices: camcorders, set-top boxes, TV sets, various audio devices, and more
> SUBSYSTEM="firewire", ATTR{specifier_id}="0x00a02d", ATTR{version}="0x010001",\
>  PROGRAM="/bin/chgrp video /dev/%P"
> 

I tried playing with rules like this about a year ago, but it didn't
work because the spec_id was only available in the child nodes of the
firewire device, so udev couldn't match on it (see more below).  Has
that changed so these work now?

> 3.e)  Aliases for firewire character devices (symlinks)
> 
> Right now no application program is known to exist that would be able to
> make use of aliases of (symlinks to) /dev/fw* character device files.
> However, I spotted the following in udev/rules/redhat/40-redhat.rules:
> 
> KERNEL="fw*", PROGRAM="fw_unit_symlinks.sh %k %n", SYMLINK+="$result"
> 
> BTW, instead of the KERNEL match, I would recommend a SUBSYSTEM match.
> 
> A web search turned up that fw_unit_symlinks.sh looks or looked like
> this:
> 
.....

> So this will create symlinks like iidc3, sbp2-7, avc5 end the likes.
> These aren't persistent (only unique), because %n will change all the
> time.  Since they provide symlinks which encode the types of available
> units on the node, these symlinks may be of (some limited) use in the
> future, provided that they would be available on all distributions.

> So, all things considered, I think we don't need any of such symlinks at
> all.
> 

Yes, I think it was me who originally came up with this symlink script.
See here:

https://bugzilla.redhat.com/show_bug.cgi?id$0770

It was created because udev rules could not see the spec_id of the
devices and we wanted to selectively chgrp iidc and avc devices to the
console owner.  Thus, this script would create named symlinks and then
udev could simply chgrp based on the filename.

Now that ACLs are used in Fedora for dealing with console ownership,
this script and its udev rule are probably not very useful to anyone.

However, for other distributions that may not use ACLs, have you
confirmed that spec_id's are truly visible to udev rules now?

-David