On Sun, 2 Nov 2003, ZHOU DX wrote: > Hi there, > > When I am working on my USB2 camera driver with > 2.4.20-20.9 (RH9.0), I get some "over-current change" > messages in my syslogs. The driver still works fine, > but the message makes me not very comfortable. Can > anyone tell me what it means? > > Thanks, > > Dan > > I am using a 4-port USB2 PCI add-on card with NEC > chips, and the /var/log/messages looks like: > > Nov 2 22:47:23 dan kernel: hub.c: port 3 over-current change > Nov 2 22:47:25 dan last message repeated 3 times > Nov 2 22:47:25 dan kernel: hub.c: port 5 over-current change > Nov 2 22:47:26 dan kernel: hub.c: port 3 over-current change > Nov 2 22:47:28 dan last message repeated 3 times > Nov 2 22:47:28 dan kernel: hub.c: port 5 over-current change
The "over-current change" message means just what it sounds like: there has been a change in the over-current status of a port on the hub. Either the condition existed and then stopped, or else it didn't exist and then started. In this case it may possibly indicate your add-on card has a problem, rather than the camera. I don't know if this excerpt from the USB 2.0 specification will prove very reassuring or informative, but it's the best I can do: 7.2.1.2.1 Over-current Protection The host and all self-powered hubs must implement over-current protection for safety reasons, and the hub must have a way to detect the over-current condition and report it to the USB software. Should the aggregate current drawn by a gang of downstream facing ports exceed a preset value, the over-current protection circuit removes or reduces power from all affected downstream facing ports. The over-current condition is reported through the hub to Host Controller, as described in Section 11.12.5. The preset value cannot exceed 5.0 A and must be sufficiently above the maximum allowable port current such that transient currents (e.g., during power up or dynamic attach or reconfiguration) do not trip the over-current protector. If an over-current condition occurs on any port, subsequent operation of the USB is not guaranteed, and once the condition is removed, it may be necessary to reinitialize the bus as would be done upon power-up. The over-current limiting mechanism must be resettable without user mechanical intervention. Polymeric PTCs and solid-state switches are examples of methods, which can be used for over-current limiting. Alan Stern ------------------------------------------------------- This SF.net email is sponsored by: SF.net Giveback Program. Does SourceForge.net help you be more productive? Does it help you create better code? SHARE THE LOVE, and help us help YOU! Click Here: http://sourceforge.net/donate/ _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
