Re: On demand modules loading with {tmp,ram}fs and udev

[Tomasz Torcz <zdzichu@irc.pl>]

On Fri, Oct 24, 2003 at 05:42:34PM -0700, Greg KH wrote:
> On Sat, Oct 25, 2003 at 02:00:18AM +0200, Tomasz Torcz wrote:
> > Hi,
> > 
> > I was thinking about small addition to tmpfs. When mounted with 'dev'
> > option, any lookup of non existing file should result in calling
> > modprobe with filename as argument.
> > When coupled with mount tmpfs over /dev (or /udev) this functionality
> > would allow on-demand module loading (as with devfs and plain old 
> > device nodes).
> 
> How will you do the mapping of /dev names to modules in kernel space?
> How are you going to know which of the 50 or so sound drivers to load
> when opening /dev/dsp?

Just call modprobe. Modprobe will check /etc/modprobe.conf for dsp
aliases and load module. Then udev will make devnode.
 
> And what's wrong with the current scheme of, "load a driver when the
> device is seen"?  This is how Linux currently works, and has been moving
> to for quite some time.  In the past we didn't have that capability, so
> the "load the driver when we open the /dev node" hack was added.

Few days ago I did dd if=something of=/dev/floppy/0; then I saw
in logs that floppy module was loaded. That was because I use devfs
which run modprobe when it's needed.
With udev dd would fail with non-existant /dev/floppy/0. There
is no mechanism to call modprobe.

I'm also surprised that"load the driver when we open the /dev node" 
is a hack. I get used to this standard Linux functionality as
something obvious. Other OSed (*BSD, Solaris etc.) don't work like
that?

-- 
Tomasz Torcz            There exists no separation between gods and men:
zdzichu@irc.-nie.spam-.pl   one blends softly casual into the other. 
Please CC.


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