Re: Hardware Inventory [was: Re: ISA slot detection on PCI systems?]

From: Patrick Mochel (
Date: Mon Jan 07 2002 - 14:19:06 EST

On Mon, 7 Jan 2002, Greg KH wrote:

> On Mon, Jan 07, 2002 at 07:11:03PM +0100, Dave Jones wrote:
> > On Mon, 7 Jan 2002, Patrick Mochel wrote:
> >
> > > One of the ideas that I've kicked around with some people here and the
> > > ACPI guys is the notion of trigger device enumeration from userspace
> > > completely.
> > >
> > > During the initramfs stage, a program (say devmgr) figures out what type
> > > of system you have, where the PCI buses are, etc. It tells the kernel this
> > > information, which then probes for existence, then loads drivers.
> >
> > Sounds remarkably like the work that Greg has been doing with hotplug
> > support.
> Yup :)
> But I wanted to rely on the existing PCI and USB core code to do the
> probing of the busses and devices, as it knows how to do this the best
> right now. Whenever it finds a new device it calls out to /sbin/hotplug
> with the device info. The userspace program at that location then loads
> the proper driver for the device, if it knows about it. This is the
> same code and process that runs when the kernel is up and running today.
> No code duplication is a good thing :)
> And the /sbin/hotplug program knows about _all_ devices that the
> currently compiled kernel can handle due to the MODULE_DEVICE_TABLE tags
> in the drivers.
> See the linux-hotplug project's documentation for more info on this:
> A paper and presentation about the linux-hotplug process:
> dietHotplug, a _very_ tiny implementation of /sbin/hotplug which is was
> created exactly for the initramfs stage:

It's very closely related; kinda like kissing cousins.

/sbin/hotplug is called from the kernel only, right?

I see no reason to change that at all for notification of devices that are
plugged in/removed by suprise.

I was thinking, though, more along the lines of triggering the probe for
devices that the kernel has a tough time finding on its own. E.g. peer
Host/PCI bridges, batteries, etc.


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