DragonFly BSD
DragonFly kernel List (threaded) for 2004-04
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Re: devfs vs udev/hotplug

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Thu, 22 Apr 2004 17:15:42 -0700 (PDT)

:Altough loading all the necessary modules when something is plugged in would
:solve this for usb, several people relied in other things; ej: floppies or
:cdroms drivers are compiled as modules in linux these days, and things now
:just don't work for them. Because altough doing cat /dev/cdromdevicenode
:will load the cdrom modules when the device node is accessed, with udev
:that device node won't exist (since it's compiled as a module and not loaded)
:and unlike with devfs, nobody will notice that someone is trying to access a
:device node which doesn't exists and load a module in consequence.

    I really don't see the problem.  Fixed devices in the system will either
    have a PCI id to match against, or they will be at known legacy locations
    that can be probed for.  Everything else will have a probable identifier.
    Why go to the trouble of creating a demand-loading system based on
    /dev access when the relatively few devices that would ever need such
    a system could simply be compiled into the kernel or their module
    loaded by default?  Or, for that matter, probed during boot by the RC
    subsystem.  There's no reason to waste time writing a filesystem
    integrated demand-loader based on an attempt to access a non-existant

    This is a case of using an elephant to solve a problem that could just
    as easily be solved by a mouse.


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