1 .. SPDX-License-Identifier: GPL-2.0-only 2 3 .. Copyright (C) 2020-21 Intel Corporation 4 5 .. _iosm_driver_doc: 6 7 =========================================== 8 IOSM Driver for Intel M.2 PCIe based Modems 9 =========================================== 10 The IOSM (IPC over Shared Memory) driver is a WWAN PCIe host driver developed 11 for linux or chrome platform for data exchange over PCIe interface between 12 Host platform & Intel M.2 Modem. The driver exposes interface conforming to the 13 MBIM protocol [1]. Any front end application ( eg: Modem Manager) could easily 14 manage the MBIM interface to enable data communication towards WWAN. 15 16 Basic usage 17 =========== 18 MBIM functions are inactive when unmanaged. The IOSM driver only provides a 19 userspace interface MBIM "WWAN PORT" representing MBIM control channel and does 20 not play any role in managing the functionality. It is the job of a userspace 21 application to detect port enumeration and enable MBIM functionality. 22 23 Examples of few such userspace application are: 24 - mbimcli (included with the libmbim [2] library), and 25 - Modem Manager [3] 26 27 Management Applications to carry out below required actions for establishing 28 MBIM IP session: 29 - open the MBIM control channel 30 - configure network connection settings 31 - connect to network 32 - configure IP network interface 33 34 Management application development 35 ================================== 36 The driver and userspace interfaces are described below. The MBIM protocol is 37 described in [1] Mobile Broadband Interface Model v1.0 Errata-1. 38 39 MBIM control channel userspace ABI 40 ---------------------------------- 41 42 /dev/wwan0mbim0 character device 43 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 44 The driver exposes an MBIM interface to the MBIM function by implementing 45 MBIM WWAN Port. The userspace end of the control channel pipe is a 46 /dev/wwan0mbim0 character device. Application shall use this interface for 47 MBIM protocol communication. 48 49 Fragmentation 50 ~~~~~~~~~~~~~ 51 The userspace application is responsible for all control message fragmentation 52 and defragmentation as per MBIM specification. 53 54 /dev/wwan0mbim0 write() 55 ~~~~~~~~~~~~~~~~~~~~~~~ 56 The MBIM control messages from the management application must not exceed the 57 negotiated control message size. 58 59 /dev/wwan0mbim0 read() 60 ~~~~~~~~~~~~~~~~~~~~~~ 61 The management application must accept control messages of up the negotiated 62 control message size. 63 64 MBIM data channel userspace ABI 65 ------------------------------- 66 67 wwan0-X network device 68 ~~~~~~~~~~~~~~~~~~~~~~ 69 The IOSM driver exposes IP link interface "wwan0-X" of type "wwan" for IP 70 traffic. Iproute network utility is used for creating "wwan0-X" network 71 interface and for associating it with MBIM IP session. The Driver supports 72 up to 8 IP sessions for simultaneous IP communication. 73 74 The userspace management application is responsible for creating new IP link 75 prior to establishing MBIM IP session where the SessionId is greater than 0. 76 77 For 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 1 80 81 The driver will automatically map the "wwan0-1" network device to MBIM IP 82 session 1. 83 84 References 85 ========== 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 and 90 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 mobile 95 broadband (2G/3G/4G) devices and connections" 96 - http://www.freedesktop.org/wiki/Software/ModemManager/
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