Re: module-init-tools/udev and module auto-loading

[Martin Schlemmer <azarah@nosferatu.za.org>]

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On Mon, 2004-02-02 at 02:10, Rusty Russell wrote:
> In message <1075674718.27454.17.camel@nosferatu.lan> you write:
> > A quick question on module-init-tools/udev and module auto-loading ...
> > lets say I have a module called 'foo', that I want the kernel to
> > auto-load.
> 
> The *idea* of udev et al is that the kernel finds the devices,
> /sbin/hotplug loads the driver etc.
> 

Right.

> This does not cover the class of things which are entirely created by
> the driver (eg. dummy devices, socket families), so cannot be
> "detected".  Many of these (eg. socket families) can be handled by
> explicit request_module() in the core and MODULE_ALIAS in the driver.
> Some of them cannot at the moment: the first the kernel knows of them
> is an attempt to open the device.  Some variant of devfs would solve
> this.
> 

I guess there will be cries of murder if 'somebody' suggested that if
a node in /dev is opened, but not there, the kernel can call
'modprobe -q /dev/foo' to load whatever alias there might have been?

Understand me correctly, I do not want devfs back.  I am just checking
if we could do something for similar behaviour.  I know it has not
_really_ hit the lists, but I have already had complaints about this
not being supported anymore.  I think the complaints will start even
more if raminitfs eventually hits functionality (as /dev will then be
then consisting only of loaded drivers (if I am not mistaken).

Once again I do not say we should give in to it, but it _does_ make
things easier.  So if there is a lightweight way to do this, then
great - and this is what I was trying to get discussion directed to.

> > Then a distant related issue - anybody thought about dynamic major
> > numbers of 2.7/2.8 (?) and the 'alias char-major-<whatever>-* whatever'
> > type modprobe rules (as the whole fact of them being dynamic, will make
> > that alias type worthless ...)?
> 
> Yes.  This could be changed to probe by device name, not number
> though.  And most names can't be dynamic: /dev/null has certain, fixed
> semantics.
> 
> The "I found this hardware, who will drive it?" mechanism of udev, and
> the "User asked for this, who will supply it?" mechanism of kmod have
> some overlap, but I think both will end up being required.
> 

Ok, was just wondering.


Thanks,

-- 
Martin Schlemmer

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