Hotplug is a separate package that hooks into the kernel through a kernel
module and does all this dynamic config change stuff. It works quite
happily in 2.4, and is developed on into 2.5/2.6. It was written really
for USB and then worked in with the PCMCIA and PCI hotplug stuff. It does
require some hooks in the device drivers.
It does not assign to users, it does give sensible names to devices. There
was also recently a patch to further help partition devices which might he
helpful here. Thus if you plug in a USB Zip drive, it will make sure that
the usb-storage module is loaded which will allocate is a /dev/sd? number.
The patch goes a bit further and creates a logical device (/dev/zipx) which
can then be the subject of a mount request. The reason for needing this is
that if you have a camera and a zip drive, which /dev/sd? you get depends
on which order you plug them in, and this makes fstab entries difficult to
use. With the patch it gets easier because you do not normally have more
than one camera or zip drive in a PC. Now on a mainframe this is more
difficult, and a slightly different approach may be required, but the
principle holds. You might for instance have the device named by its
label, so /dev/dasd/<label> rather than /dev/dasd? where ? is a number. I
think the framework is flexible enough to do this.
David
Alan Altmark
<[EMAIL PROTECTED] To: [EMAIL PROTECTED]
s.ibm.com> cc:
Sent by: Linux Subject: Re: Linux390 + VM + Tape 3490
on 390 Port
<[EMAIL PROTECTED]
ARIST.EDU>
13/06/2003
15:00
Please respond
to Linux on 390
Port
On Friday, 06/13/2003 at 02:28 CET, David Goodenough
<[EMAIL PROTECTED]> wrote:
> This sounds a lot like the kind of processing that hotplug should do?
>
> David
In 2.5/2.6, things will change because of the generalized Linux support
for dynamic I/O config changes, with automatic execution of device
startup/cleanup scripts, etc. (If that's what you mean by "hotplug"....
not sure what the official Linux name for this function is.) But I think
you do not want automatic assignment of a drive that comes online
(attached, in VM terms). That needs to wait until the drive is actually
needed.
The point is that assignment of a drive when it comes online or at driver
load time prevents any kind of multi-host sharing. It's not a Linux
problem, per se, but a driver issue.
The real point of discussion is whether the mt, UTS or a combination
approach is best. One of the advantages I see in the UTS approach is that
the driver can prevent access to the standard label, just as the dasd
drivers do for disks.
Alan Altmark
Sr. Software Engineer
IBM z/VM Development
