Documentation/networking/cdc_mbim.rst

Source file repositories/reference/linux-study-clean/Documentation/networking/cdc_mbim.rst

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Documentation/networking/cdc_mbim.rst
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.. SPDX-License-Identifier: GPL-2.0

======================================================
cdc_mbim - Driver for CDC MBIM Mobile Broadband modems
======================================================

The cdc_mbim driver supports USB devices conforming to the "Universal
Serial Bus Communications Class Subclass Specification for Mobile
Broadband Interface Model" [1], which is a further development of
"Universal Serial Bus Communications Class Subclass Specifications for
Network Control Model Devices" [2] optimized for Mobile Broadband
devices, aka "3G/LTE modems".


Command Line Parameters
=======================

The cdc_mbim driver has no parameters of its own.  But the probing
behaviour for NCM 1.0 backwards compatible MBIM functions (an
"NCM/MBIM function" as defined in section 3.2 of [1]) is affected
by a cdc_ncm driver parameter:

prefer_mbim
-----------
:Type:          Boolean
:Valid Range:   N/Y (0-1)
:Default Value: Y (MBIM is preferred)

This parameter sets the system policy for NCM/MBIM functions.  Such
functions will be handled by either the cdc_ncm driver or the cdc_mbim
driver depending on the prefer_mbim setting.  Setting prefer_mbim=N
makes the cdc_mbim driver ignore these functions and lets the cdc_ncm
driver handle them instead.

The parameter is writable, and can be changed at any time. A manual
unbind/bind is required to make the change effective for NCM/MBIM
functions bound to the "wrong" driver


Basic usage
===========

MBIM functions are inactive when unmanaged. The cdc_mbim driver only
provides a userspace interface to the MBIM control channel, and will
not participate in the management of the function. This implies that a
userspace MBIM management application always is required to enable a
MBIM function.

Such userspace applications includes, but are not limited to:

 - mbimcli (included with the libmbim [3] library), and
 - ModemManager [4]

Establishing a MBIM IP session requires at least these actions by the
management application:

 - open the control channel
 - configure network connection settings
 - connect to network
 - configure IP interface

Management application development
----------------------------------
The driver <-> userspace interfaces are described below.  The MBIM
control channel protocol is described in [1].


MBIM control channel userspace ABI
==================================

Annotation

Implementation Notes