Re: hotplug TTD

[David Brownell <david-b@pacbell.net>]

> So. What needs to be done to finish this thing?

Can one "finish" software, ever?  :-)


A few things on my mind:  move the hotplug scripts to this new
linux-hotplug project. Create better hotplug docs, put them on
the a website.  Maybe the hotplug programs should turn into C
programs not scripts, who knows.  Volunteers?


Technically, there are open issues I think need to be addressed.

First, get hotplugging back to the behavior I saw in about test11,
which is bugfixing and testing.  Call this "kernel 2.4.1 work" for
the most part; basically, hotplugging for USB, PCI/Cardbus, and
NETworking should all work smoothly.

    - Sync up with the 2.4.0-final ABI change for usb_device_id,
      including "usbutils" and various bugs (usb-serial etc) that
      snuck in with that change.  (I think modutils is set.)

    - More testing on the "new" user mode hotplug scripts (which
      use /etc/hotplug exclusively) ... adding a PCI hotplug agent
      (steal from the old one).

    - Find out what's up with those async changes (test12) that
      sometimes seem to wedge things when I modprobe a USB HCD
      for a controller that's got a network adapter pre-connected.
      (Andrew, I've not yet made time to try your sync/async patch
      putting USB back in pure synchronous mode; chasing an oops.)

    - Similarly for the PCI/Cardbus hotplug situation; Miles has
      reported problems there.

    - Are those network API changes a 2.4.1 issue -- replacing
      init_etherdev() with prepare_etherdev()/withdraw_netdev() ?
      It was my understanding they were needed to cleanly do
      network hotplugging.

I think that all USB devices other than some of the funkier HID
devices should be ready to hotplug at this time ... the main win
from that ABI change was simpler handling for usb-storage, but we
got some destabilization too.

Second, there are various types of related functionality to be
developed.  Addressing the "can't hotplug during boot" issue
(something kudzu-like to scan /proc/bus/{usb,pci}/*/* and create
hotplug events).  Some sort of generic analogue to "cardctl eject"
would be good.  And as Miles noted, "pcmcia_cs" is a degenerate
case of (generic) hotplug ...

There's also device/driver specific initialization that we should
understand better.  We know how to ensure that a USB controller
(on any PCI bus) is cleanly initted.  I don't think we know how
to do that for a disk drive (start with SCSI and generalize) or
printer.

- Dave




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