Bjørn Mork <bjorn@xxxxxxx> writes: > Måns Rullgård <mans@xxxxxxxxx> writes: >> Dan Williams <dcbw@xxxxxxxxxx> writes: >> >>> TLDR; some firmware uses the DTR signal as an indicator to come out of >>> low-power mode. Without doing so you cannot talk to the modem over any >>> of it's ports, QMI, net, or serial. >> >> I must be missing something, but how does a network interface have a DTR >> signal? > > It does not. But the network function is (ab)using the Comm class USB > control message "SetControlLineState" to signal "wake up" from the host > to the device. Which is perfectly fine since the USB function in > question is vendor specific. The vendor can define any USB control > message to mean anything they want. Reusing a Comm class message > probably made sense to the firmware engineer designing this. We can > only note and adapt. > > It doesn't have anything to do with DTR. Every time you think USB can't get any worse, it does. -- Måns Rullgård
