Re: usbd config file parse behaviour

From: Sam Lawrance (boris_at_brooknet.com.au)
Date: 03/31/04

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    Date: Wed, 31 Mar 2004 14:11:07 +1000 (EST)
To: ticso@cicely.de

    > On Tue, Mar 30, 2004 at 01:46:32AM -0700, M. Warner Losh wrote:
    >> In message: <20040330083607.GC32646@cicely12.cicely.de>
    >> Bernd Walter <ticso@cicely12.cicely.de> writes:
    >> : On Mon, Mar 29, 2004 at 07:44:34PM -0700, M. Warner Losh wrote:
    >> : > In message: <1080613926.1125.6.camel@dirk>
    >> : > Sam Lawrance
    >> <samuel.lawrance@studentmail.newcastle.edu.au> writes:
    >> : > : On Sun, 2004-03-28 at 20:47, Bernd Walter wrote:
    >> : > : > On Sun, Mar 28, 2004 at 01:31:03AM -0700, M. Warner Losh wrote:
    >> : > : > > Btw, any interest in making it possible to kldload a usb
    >> module and
    >> : > : > > having device attach to it? Right now the usb code assumes
    >> that you
    >> : > : > > can unplug the device and replug it back in. I have at least
    >> two
    >> : > : > > devices on my laptop that can't be removed (bluetooth and
    >> memory stick
    >> : > : > > reader), so I can't dynamically load drivers for them...
    >> : > : >
    >> : > : > I'll think about it.
    >> : > : > Reprobing is not so much an issue as selecting an interface for
    >> it.
    >> : > :
    >> : > : would this done by filling in uhub_driver_added() to find a better
    >> : > : driver match for a device and reattaching?
    >> : >
    >> : > Yes. Actually, it also requires some changes to newbus as well to
    >> : > allow for rebidding of devices. And there's some minor resetting of
    >> : > the device that likely needs to happen, but that's lower priority.
    >> :
    >> : Don't forget that we already have a driver for every USB device:
    >> ugen(4)
    >> : We need a better trigger to reprobe drivers - thats the real problem.
    >>
    >> No. That's not the real problem here. The real problem here is that
    >> uhub doesn't implement the driver_added callback correctly. The ugen
    >> issue, while interesting, can be overcome by not having ugen in the
    >> kernel.
    >
    > Not having ugen in the kernel is not an option.
    > I can't say that I really like the problems introduced by ugen, but
    > since I have no better idea and ugen is widely used - even by me.
    >
    >> When ugen is in the kernel, we do need to do the rebid thing in
    >> newbus, which we don't do, but there's little point in fixing one w/o
    >> fixing the other.
    >
    > You can't kldload a new driver and reshuffeling all ugen instances.
    > They are possibly used and probing for USB devices requires exclusive
    > access in many cases.
    >
    > I'm more thinking about some kind of userland tool that allows
    > retriggering an USB device in a controlled way.
    > Such a feature is required for some types of firmware downloaders too.
    > Intelligent USB chips requireing firmware download could disconneect
    > and reconnect themself from the bus e.g. the TI-TUSB* family, but
    > there are still others in the wild.
    > I've seen firmware downloaders to do evil things as reseting an USB
    > ports on their own, which is quite dangerously as it introduces a
    > race for having multiple devices with address 0 (the default for
    > freshly attached ones).

    I agree that it's bad to yank a device from under ugen automatically and
    reattach it to a better match.
    How about adding a new ioctl on /dev/usb, eg USB_REPROBE to reset a device
    if a better match exists?
    Could tack an option on to usbdevs to call it on requested devices.

    -Sam

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