On Jan 20, 2010, at 8:25 AM, Michal Hlavinka wrote:

I'd like to know your opinion for bug
http://bugzilla.redhat.com/show_bug.cgi?id=544121

Recently serial connected UPSes stopped working because ModemManager steals tty devices (it tries to open every tty device to check if there is modem sitting there), this means device is blocked for about 10 seconds. This prevents nut daemon to start. I've reassigned bug against ModemManager because I think it's its fault, but ModemManager maintainer says it nut fault, because nut should not give up to open device and it should retry later. What do you
think? Some more details can be found in the bug comments.

If ModemManager probes serial devices, IMHO it should be optional, and easy to disable. At the very least, there should be an option to block ModemManager from using a specific port.

Sending AT commands to an UPS is not well-defined. Some UPSes may handle this gracefully, but I think that if someone has an UPS connected to a system, the uptime requirements of the system are probably more important than the convenience of auto-detecting a modem.

We have auto-reconnect code for some USB devices (only after the device has been opened successfully, IIRC) and it is a mess. I personally don't think we should add similar complexity to the serial side of NUT, and if we do, it should be disabled by default.

--
Charles Lepple

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