Re: Module Ideas: Persistence, PnP, and more...

Alon Ziv (alonz@cs.Technion.AC.IL)
Sat, 5 Sep 1998 02:42:03 +0300 (IDT)


On Fri, 4 Sep 1998, David Howells wrote:
> > 2. Plug-and-Play support
> >
> > To properly support PnP, we need a method for userspace `bus managers' to
> > identify drivers by their IDs on thebus, and to configure them.
>
> This is what I envision happening in the configuration manager I wrote:
>

Whoa. This looks infernally complex; are you *sure* it all belongs in the
kernel?

> 1) The idea is for the kernel to tell insmod (or some similar tool) that it
> wants a particular device or class of device.

Why do you put the configuration manager in the kernel? Isn't it enough
to have (at most) a bus-scan module, and put the configuration manager
itself in userspace?

> 2) insmod would then scan module files for "tag tables" which describe the
> range of devices that a driver can handle (by device ID or by device
> class), and should it find a suitable module, it would then load it.

My idea is to leave this to modprobe, with suitable depmod support to
build an index of IDs (tags) <-> modules. The index may well be just a
file of aliases, in the form `alias isapnp-DFX0000_1493 serial'.

> 3) Whilst loading, the module would register it's drivers with the cmgr.
> 4) The cmgr would then look through the tags tables pointed to by the drivers,
> and attach devices appropriately.
> 5) Whilst attaching a device to a driver, the cmgr will negotiate a
> configuration between the device config interface (PnP, PCI, etc), the
> driver, and any conflicting devices on the system.

This is the overly complex part.
Why not just let a userspace configuration manager decide on appropriate
settings *before* it loads the module, and pass them at insmod time?

I explained my method for this in one of my previous postings.

If a conflict is detected, and it requires changing some other driver's
settings, it will probably require shutting down the other driver and
reloading it in any case. If an irreconcilable conflict is detected...
Well, it's irreconcilable!

-az

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