On Tue, May 6, 2014 at 9:42 PM, Dan Williams <dcbw@xxxxxxxxxx> wrote: > On Tue, 2014-05-06 at 14:27 +0530, Suresh Kumar N. wrote: >> On Mon, May 5, 2014 at 8:38 PM, Dan Williams <dcbw@xxxxxxxxxx> wrote: >> > 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) >> >> In such case (pseudo-ethernet NIC) do we assume that the firmware on >> the USB Dongle is responsible to establish IP address? >> In other words how does IP address allocation occur in this case? > Thank you very much for such a clear and exhaustive explanation. > The firmware is always involved, because the IP address comes from the > cellular network, and the firmware is what receives it. The firmware > must then provide that address to the host, so that the host can > communicate with the network. This happens in a few ways: > > 1) firmware implements a DHCP server, IPv6 Router, etc; host uses DHCP > client or IPv6 Router Discovery to obtain IP address and DNS details > > 2) firmware provides static IP address and DNS details over AT commands > > 3) firmware provides static IP address and DNS details via proprietary > protocols (QMI, MBIM, etc) > > 4) firmware implements PPP over serial port and provides IP address and > DNS details via IPCP/IPV6CP Based on 1) and 2), Firmware refers to be driver code implemented on USB device-side, but 3) and 4) refer to Firmware implemented on Host-side. Does Firmware here refer to Host-side or USB device-side? > > Most modems still support #4 over at least one AT-capable serial port. > Many modems implement multiple methods (eg, Qualcomm firmware often does > #1, #3, and #4). > > Note that in all cases, connection setup (with the APN and other > details) must occur via control channels (with AT, QMI, MBIM, etc) > before you can use any of these methods to obtain an IP address from the > firmware. > > There is actually another class of "plug and play" 3G dongle that > provides a NAT-ed IP network (192.168.0.x or 10.x) to the host over what > looks like a USB ethernet NIC. These appear exactly like a normal USB > ethernet dongle or a home router to the host, and to configure the > device, you use a web browser on the host like you would with a home > router. None of the 3G stuff is exposed to the host. One example is > Huawei HiLink devices like the E3256, though not all HiLink-branded > devices operate this way. In all of the above, how do we visualize the Connect/Disconnect option provided by the Host side application? 1. Is it defined to just Enable/Disable a network interface (USB ethernet NIC) on Host side, but in that case would the Active context get Deactivated? OR 2. Is it defined to Activate/Deactivate context? > > Dan > >> > 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 >> >> Thanks for the information. >> >> > >> > 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 > > -- 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
