Re: udev-021 rule based permissions (+patch)

[Greg KH <greg@kroah.com>]

On Wed, Mar 03, 2004 at 04:34:43PM +0100, Hyriand wrote:
> On Wednesday 03 March 2004 16:10, you wrote:
> > On Wed, Mar 03, 2004 at 03:15:45PM +0100, Hyriand wrote:
> > > Dear Greg,
> > >
> > > First of all, thanks for your excellent work on udev (and related tools),
> > > I really enjoyed giving devfs a big kick and wiping every trace of it
> > > from my kernel.
> >
> > Thanks for your kind words.
> >
> > > But now for the direct cause of this e-mail, rule-based permissions.
> > > Quite simple actually, it adds OWNER, GROUP and MODE fields to the device
> > > rules, and applies those if no applicable rule is found in the
> > > permissions table. I know this might be against conventions, but it adds
> > > some flexibility since you can't change permissions based on a symlink
> > > name.
> >
> > Hm, I don't understand.  What is wrong with the current scheme of using
> > the udev.permissions file for this?
> 
> An over-simplified case would be a laptop that has a slot in which you can 
> insert a cd-recorder or a dvd-rom drive. If the cd-rw is inserted, the group 
> of the "hdc" device should be "cdrw" (well, depends on how you arrange 
> security of course), and if the dvd-rom drive is inserted, the group should 
> be something else. There's currently one way of achieving that, making the 
> device name change (cdrom or dvdrom), settings up permissions for that and 
> symlinking it to %k (for compatibility reasons), but I thought this was a 
> slightly cleaner way (configuration wise) of setting up different permissions 
> for a device without having to symlink it.
> 
> Or in other words, "hdc" (or whatever other device file) might not always 
> refer to the same device, and should have different permissions accordingly.

Then provide a different name for the device, which allows you to have
different permissions.  That's the simplest solution for this, correct?

thanks,

greg k-h


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