Re: [Libusb-devel] udev craze: need /dev/bus/usb rationale

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

On Thu, Jan 26, 2006 at 06:26:15PM -0800, Johannes Erdfelt wrote:
> On Fri, Jan 27, 2006, Kay Sievers <kay.sievers@vrfy.org> wrote:
> > On Thu, Jan 26, 2006 at 06:08:11PM -0800, Johannes Erdfelt wrote:
> > > I want to understand the reason for these device nodes since they seem
> > > to duplicate the nodes found in /proc/bus/usb. Is this just part of the
> > > long term plans to remove usbdevfs?
> > 
> > Yes, we want to leave /proc with all stuff that isn't process related.
> > And as all the major distros depend on udev and have /dev on tmpfs, having
> > usb devices in /proc makes no sense anymore.
> > 
> > We also want the option to apply access control lists to device nodes,
> > to allow a set of users (fast-user-switching) access to a device and
> > this would not work with /proc files, which can only have primary
> > ownership.
> 
> Ahh, sounds great. I've checked in the change to CVS. It will only check
> /dev/bus/usb and /proc/bus/usb now, in that order.

Sounds good.

> I haven't seen any of the conversations about this,

There are no real discussions about. It just "happened" as I stumbled
across the lack of ACL support while thinking about a possible successor
for Red Hat's pam_console and SUSE's resmgr, that should become a common
service for granting access rights on Linux instead of the distro
specific mess we currently fighting against.

> but what will happen to /proc/bus/usb/devices?

It needs to be mounted to be active, so the option to use it is still there.
For SUSE we just leave it enabled in the kernel for now but don't mount it.
So users that depend on the /proc nodes, for whatever reason, can just mount
it and get the old behavior.

Our libusb patch first looks for /proc, but the other way around like you
checked into CVS is fine too, cause it's just one udev rule that need to be
commented out then to switch the behavior.

After a while we will know what needs to be fixed and then when we can remove
usbdevfs entirely from the kernel.

> Unrelated, but I may make a 0.1.12 release sometime soon because there
> have been a surprising amount of changes since 0.1.11 was released.

Nice. Thanks!

Kay


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