func scanLoop(jaz *app) {
        for {
                jaz.logf("scanLoop: starting")
                opt := jaz.options.Get()
                begin := time.Now()
                dev.Scan(jaz.table, jaz.table.ListDevices(), jaz.logger, opt, jaz.requestChan)
                elap := time.Since(begin)
                sleep := opt.ScanInterval - elap
                if sleep < 1 {
                        sleep = 0
                }
                jaz.logf("scanLoop: sleeping for %s (target: scanInterval=%s)", sleep, opt.ScanInterval)
                time.Sleep(sleep)
        }
}