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96 lines
3.6 KiB
96 lines
3.6 KiB
.. SPDX-License-Identifier: GPL-2.0-only |
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.. Copyright (C) 2020-21 Intel Corporation |
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.. _iosm_driver_doc: |
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=========================================== |
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IOSM Driver for Intel M.2 PCIe based Modems |
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=========================================== |
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The IOSM (IPC over Shared Memory) driver is a WWAN PCIe host driver developed |
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for linux or chrome platform for data exchange over PCIe interface between |
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Host platform & Intel M.2 Modem. The driver exposes interface conforming to the |
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MBIM protocol [1]. Any front end application ( eg: Modem Manager) could easily |
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manage the MBIM interface to enable data communication towards WWAN. |
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Basic usage |
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=========== |
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MBIM functions are inactive when unmanaged. The IOSM driver only provides a |
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userspace interface MBIM "WWAN PORT" representing MBIM control channel and does |
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not play any role in managing the functionality. It is the job of a userspace |
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application to detect port enumeration and enable MBIM functionality. |
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Examples of few such userspace application are: |
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- mbimcli (included with the libmbim [2] library), and |
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- Modem Manager [3] |
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Management Applications to carry out below required actions for establishing |
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MBIM IP session: |
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- open the MBIM control channel |
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- configure network connection settings |
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- connect to network |
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- configure IP network interface |
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Management application development |
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================================== |
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The driver and userspace interfaces are described below. The MBIM protocol is |
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described in [1] Mobile Broadband Interface Model v1.0 Errata-1. |
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MBIM control channel userspace ABI |
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---------------------------------- |
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/dev/wwan0mbim0 character device |
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
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The driver exposes an MBIM interface to the MBIM function by implementing |
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MBIM WWAN Port. The userspace end of the control channel pipe is a |
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/dev/wwan0mbim0 character device. Application shall use this interface for |
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MBIM protocol communication. |
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Fragmentation |
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~~~~~~~~~~~~~ |
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The userspace application is responsible for all control message fragmentation |
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and defragmentation as per MBIM specification. |
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/dev/wwan0mbim0 write() |
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~~~~~~~~~~~~~~~~~~~~~~~ |
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The MBIM control messages from the management application must not exceed the |
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negotiated control message size. |
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/dev/wwan0mbim0 read() |
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~~~~~~~~~~~~~~~~~~~~~~ |
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The management application must accept control messages of up the negotiated |
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control message size. |
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MBIM data channel userspace ABI |
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------------------------------- |
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wwan0-X network device |
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~~~~~~~~~~~~~~~~~~~~~~ |
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The IOSM driver exposes IP link interface "wwan0-X" of type "wwan" for IP |
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traffic. Iproute network utility is used for creating "wwan0-X" network |
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interface and for associating it with MBIM IP session. The Driver supports |
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upto 8 IP sessions for simultaneous IP communication. |
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The userspace management application is responsible for creating new IP link |
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prior to establishing MBIM IP session where the SessionId is greater than 0. |
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For example, creating new IP link for a MBIM IP session with SessionId 1: |
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ip link add dev wwan0-1 parentdev-name wwan0 type wwan linkid 1 |
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The driver will automatically map the "wwan0-1" network device to MBIM IP |
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session 1. |
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References |
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========== |
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[1] "MBIM (Mobile Broadband Interface Model) Errata-1" |
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- https://www.usb.org/document-library/ |
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[2] libmbim - "a glib-based library for talking to WWAN modems and |
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devices which speak the Mobile Interface Broadband Model (MBIM) |
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protocol" |
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- http://www.freedesktop.org/wiki/Software/libmbim/ |
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[3] Modem Manager - "a DBus-activated daemon which controls mobile |
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broadband (2G/3G/4G) devices and connections" |
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- http://www.freedesktop.org/wiki/Software/ModemManager/
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