Re: Permissions of usb hub and its children

[Greg KH <greg@kroah.com>]

On Tue, Sep 05, 2006 at 11:50:03PM +0200, Fabian Steiner wrote:
> Greg KH wrote:
> > On Tue, Sep 05, 2006 at 11:52:54AM +0200, Fabian Steiner wrote:
> >> Hello!
> >>
> >> I am trying to change the permissions of my usb hub with the follwing
> >> udev rule:
> >>
> >> SUBSYSTEM="usb", DEVPATH="/devices/pci0000:00/0000:00:02.1/usb1/1-3",
> >> OWNER="fabi", MODE="600
> > 
> > What are you trying to change here?  The permissions of the usb hub in
> > usbfs?
> 
> Yes, my intension was to assign proper permissions to the usb hub so
> that all devices that are connected to that hub get the same permissions.

Ah, multi-user type setup?

> >> Doing so I hoped that all usb devices that will be connected to that hub
> >> would receive the same permissions but obviously it doesn't work.
> > 
> > No, hub permissions do not propagate down to the devices, sorry.
> > 
> >> Is there any possibility to achieve this goal using udev?
> > 
> > Yes, use much the same rule as above :)
> 
> What does the rule have to look like then? ;-) The main problem is that
> I don't know what kind of devices are plugged in the hub. So the udev
> rule has to match quite a lot of devices (block devices, scanner, mouse,
> etc.).
> 
> Having a more closer look at different manpages and howtos I have found
> a solution that is almost suitable:
> 
> SUBSYSTEM="*",
> ENV{PHYSDEVPATH}="/devices/pci0000:00/0000:00:02.1/usb1/1-3*",
> OWNER:="fabi", MODE:="600"
> 
> I am not quite sure whether this rule will fulfill all of my
> requirements but so far it looks good. I.e. I don't know for sure
> whether ENV{PHYSDEVPATH} is set for all devices and whether it contains
> a sysfs address. Perhaps you could give me a hint :-)

Yes, that should work.  But remember, "usb1" the next time you boot
might not be the same root hub you thought it was last time.  That all
depends on PCI bus numbering (which can change, but rarely), and USB
host controller driver loading order (which changes often due to the
phase of the moon and such.)

So be careful about that.

good luck,

greg k-h

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