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1.. SPDX-License-Identifier: GPL-2.0-only2 3.. Copyright (C) 2020-21 Intel Corporation4 5.. _iosm_driver_doc:6 7===========================================8IOSM Driver for Intel M.2 PCIe based Modems9===========================================10The IOSM (IPC over Shared Memory) driver is a WWAN PCIe host driver developed11for linux or chrome platform for data exchange over PCIe interface between12Host platform & Intel M.2 Modem. The driver exposes interface conforming to the13MBIM protocol [1]. Any front end application ( eg: Modem Manager) could easily14manage the MBIM interface to enable data communication towards WWAN.15 16Basic usage17===========18MBIM functions are inactive when unmanaged. The IOSM driver only provides a19userspace interface MBIM "WWAN PORT" representing MBIM control channel and does20not play any role in managing the functionality. It is the job of a userspace21application to detect port enumeration and enable MBIM functionality.22 23Examples of few such userspace application are:24- mbimcli (included with the libmbim [2] library), and25- Modem Manager [3]26 27Management Applications to carry out below required actions for establishing28MBIM IP session:29- open the MBIM control channel30- configure network connection settings31- connect to network32- configure IP network interface33 34Management application development35==================================36The driver and userspace interfaces are described below. The MBIM protocol is37described in [1] Mobile Broadband Interface Model v1.0 Errata-1.38 39MBIM control channel userspace ABI40----------------------------------41 42/dev/wwan0mbim0 character device43~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~44The driver exposes an MBIM interface to the MBIM function by implementing45MBIM WWAN Port. The userspace end of the control channel pipe is a46/dev/wwan0mbim0 character device. Application shall use this interface for47MBIM protocol communication.48 49Fragmentation50~~~~~~~~~~~~~51The userspace application is responsible for all control message fragmentation52and defragmentation as per MBIM specification.53 54/dev/wwan0mbim0 write()55~~~~~~~~~~~~~~~~~~~~~~~56The MBIM control messages from the management application must not exceed the57negotiated control message size.58 59/dev/wwan0mbim0 read()60~~~~~~~~~~~~~~~~~~~~~~61The management application must accept control messages of up the negotiated62control message size.63 64MBIM data channel userspace ABI65-------------------------------66 67wwan0-X network device68~~~~~~~~~~~~~~~~~~~~~~69The IOSM driver exposes IP link interface "wwan0-X" of type "wwan" for IP70traffic. Iproute network utility is used for creating "wwan0-X" network71interface and for associating it with MBIM IP session. The Driver supports72up to 8 IP sessions for simultaneous IP communication.73 74The userspace management application is responsible for creating new IP link75prior to establishing MBIM IP session where the SessionId is greater than 0.76 77For example, creating new IP link for a MBIM IP session with SessionId 1:78 79 ip link add dev wwan0-1 parentdev-name wwan0 type wwan linkid 180 81The driver will automatically map the "wwan0-1" network device to MBIM IP82session 1.83 84References85==========86[1] "MBIM (Mobile Broadband Interface Model) Errata-1"87 - https://www.usb.org/document-library/88 89[2] libmbim - "a glib-based library for talking to WWAN modems and90 devices which speak the Mobile Interface Broadband Model (MBIM)91 protocol"92 - http://www.freedesktop.org/wiki/Software/libmbim/93 94[3] Modem Manager - "a DBus-activated daemon which controls mobile95 broadband (2G/3G/4G) devices and connections"96 - http://www.freedesktop.org/wiki/Software/ModemManager/97