On Mon, 17 Jul 2006, Aras Vaichas wrote: > Eventually they ran the test with the laptop disconnected and then > reconnected > our device to see if it still worked after each type of test. It took a while > longer, but we passed.
That's good. > >>* Is there something in the USB host management code that ignores a USB > >>device > >>which is acting strangely? > > > > Yes, there is. If a device fails to enumerate after 4 attempts, the USB > > stack will ignore it until a disconnect event occurs. However, at each > > reconnect everything should restart from the beginning. So when those > > electrical pulses stopped, the device should have been enumerated > > correctly. > > Is that in the USB specification? No, it's just the way the Linux USB stack is written. Other operating systems will behave differently. > > It would be better to tackle the shortcomings of the host by fixing the > > host's software. To start with, you should compile the host's kernel with > > CONFIG_USB_DEBUG and then post the host's system log for the test period. > > I'll try and include some form of host logging for the next barrage of tests > if > I can. I couldn't do anything this time because we couldn't delay the tests > and > miss our pre-booked (and expensive) testing window. > > I'll try and think of a way to simulate this test in the office if I can. I > think the test was a short 1000V pulse, every 300ms on the power line. It > must > have caused the ground to bounce around relative to the laptop which detected > it as a USB disconnect (I guess). I could probably rig up something similar > that applies the same principle to the USB cable (not with a 1000V though!). These rapid repeated disconnects are a kind of stress testing the Linux USB host code is hardly ever exposed to. It's not surprising that eventually it would fail. Alan Stern ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel