On Thu, 18 Mar 2004, Alan Stern wrote:
> On Thu, 18 Mar 2004, David Brownell wrote:
>
> > Matthias Andree wrote:
> > > I call it excessive because I wonder if it's correct to feed a hotplug
> > > event just because $USER_SPACE_PROGRAM has decided to open a
> > > /proc/bus/usb/MMM/NNN device.
> >
> > Are you sure that's what's making it happen? Or is your
> > software maybe trying to set the configuration? That would
> > get rid of the old devices, and create new ones.
>
> Something definitely is setting the configuration. The interface
> registration events are in the system log.
>
> > Software that tries to change the device configuration would
> > certainly cause lots of hotplugging. Basically that's a bad
> > idea. There's a call to just _reset_ the configuration, that
> > verges on reasonable ... for devices that only have a single
> > driver on the device interfaces.
>
> That's part of the problem. Another part is that whatever program is
> running as the hotplug agent is using timeouts of 0.1 seconds to read the
> device and configuration descriptors. It should be using something more
> like 5 seconds.
I believe I've identified the trigger of the problem. Log attached
(Linux 2.6), with usb.agent running with "set -x".
I don't understand why this hotplug version executes several processes
of usb.agent for the same device at the same time, but that's probably
off-topic for this list.
Hotplug's usb.agent runs usbmodules, and just sampling one of the
usbmodules invocations from the log and feeding them through strace
yields:
...
close(3) = 0
munmap(0x40016000, 4096) = 0
open("/proc/bus/usb/003/002", O_RDWR) = 3
ioctl(3, USBDEVFS_CONTROL, 0xbfffefb0) = 18
ioctl(3, USBDEVFS_CONTROL, 0xbfffeb70) = 9
ioctl(3, USBDEVFS_CONTROL, 0xbfffeb70) = 32
close(3) = 0
exit_group(0) = ?
So we do know that usbmodules run on behalf of hotplug issues
USBDEVFS_CONTROL.
I'll now see what 2.4 does and spam Yet Another Log into this list.
--
Matthias Andree
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