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Re: (Semi-random) thoughts on device tree structure and devfs

On Mon, 08 Mar 2010 01:56:28 +0100
Johnny Billquist <> wrote:

> If you want predictable device enumetaion, you can have that, and have 
> been able to have that for over twenty years...
The problem is: Over twenty years ago a hardware reconfiguration was a
infrequent and intrusive task. It required a power down and probably
rewireing the NPR grand chain on your UniBus backplane with a wire wrap
tool... System configuration was static in those good, old days where
Unix machines where administered by a professional sysadmin and cost a

Today we have all sorts of hot plug devices. SCSI, SAS, FibreChannel,
(e)SATA, USB, FireWire, PCcard, ExpressCard, hot plugable PCI(-Express),
Bluetooth, ... System configuration is verry dynamic today and every
user is its own Root. We need a better way to deal with this.

Linux had a devfs and droped it. Now it has udevd(8). Most likely the
penguins had a reason for this. udevd(8) gives the user land control
over device enumeration. Maybe no bad idea. (Disclaimer: I don't like

BTW: OSF/1 aka DEC-Unix aka Tru64-Unix did somthing like Linux +
udevd(8) over 10 years ago.



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