On Mon, 2014-05-05 at 11:07 +0530, Suresh Kumar N. wrote: > Hi, > > I am new to udev and device enumeration. > > I am interested to know how USB Data Card would get enumerated. > > Based on my understanding Data Card can get enumerated below 2 possible ways - > 1. As a modem > 2. As a Network Interface Card (NIC) Or both at the same time. > Is there a Standard defining the way a Data Card should be enumerated? There is no single standard. There is a few "standards" and multiple proprietary mechanisms, and sometimes these are combined in the same device. The device simply enumerates as a normal USB device, providing to the host computer one or more USB interfaces. Each USB interface can be any one of: 1) serial interface (AT, QCDM, WMC, WDM, CDC-ACM, etc) 2) pseudo-ethernet NIC (proprietary, CDC-ETHER, CDC-NCM, etc) 3) proprietary control protocols (CnS, QMI, etc) 4) standard non-serial control protocols (MBIM) A modem can provide any of these in combination. Which port speaks what protocol is detected by one or more of the following methods: a) USB VID/PID and interface number hardcoded in the drivers or in userland udev rules b) USB interface type (eg, serial port or NIC port, done in userland) c) probing with known request/response to determine different communication protocols used if the port type is indeterminate Dan > Please correct if my understanding is not correct or incomplete. > > Thanks in advance for your clarifications. > > Warm Regards, > Suresh > -- > To unsubscribe from this list: send the line "unsubscribe linux-usb" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
