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docs: networking: convert cdc_mbim.txt to ReST

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- add SPDX header;
- mark code blocks and literals as such;
- use :field: markup;
- adjust identation, whitespaces and blank lines;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Mauro Carvalho Chehab 2020-04-28 00:01:25 +02:00 committed by David S. Miller
parent a362032eca
commit 92f06f4226
2 changed files with 47 additions and 30 deletions
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76
Documentation/networking/cdc_mbim.txt → Documentation/networking/cdc_mbim.rst
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@ -1,5 +1,8 @@
cdc_mbim - Driver for CDC MBIM Mobile Broadband modems
========================================================
.. 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
@ -19,9 +22,9 @@ by a cdc_ncm driver parameter:
prefer_mbim
-----------
Type: Boolean
Valid Range: N/Y (0-1)
Default Value: Y (MBIM is preferred)
: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
@ -44,11 +47,13 @@ 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 reequires at least these actions by the
management application:
- open the control channel
- configure network connection settings
- connect to network
@ -76,7 +81,7 @@ complies with all the control channel requirements in [1].
The cdc-wdmX device is created as a child of the MBIM control
interface USB device. The character device associated with a specific
MBIM function can be looked up using sysfs. For example:
MBIM function can be looked up using sysfs. For example::
bjorn@nemi:~$ ls /sys/bus/usb/drivers/cdc_mbim/2-4:2.12/usbmisc
cdc-wdm0
@ -119,13 +124,15 @@ negotiated control message size.
/dev/cdc-wdmX ioctl()
--------------------
---------------------
IOCTL_WDM_MAX_COMMAND: Get Maximum Command Size
This ioctl returns the wMaxControlMessage field of the CDC MBIM
functional descriptor for MBIM devices. This is intended as a
convenience, eliminating the need to parse the USB descriptors from
userspace.
::
#include <stdio.h>
#include <fcntl.h>
#include <sys/ioctl.h>
@ -178,7 +185,7 @@ VLAN links prior to establishing MBIM IP sessions where the SessionId
is greater than 0. These links can be added by using the normal VLAN
kernel interfaces, either ioctl or netlink.
For example, adding a link for a MBIM IP session with SessionId 3:
For example, adding a link for a MBIM IP session with SessionId 3::
ip link add link wwan0 name wwan0.3 type vlan id 3
@ -207,6 +214,7 @@ the stream to the end user in an appropriate way for the stream type.
The network device ABI requires a dummy ethernet header for every DSS
data frame being transported. The contents of this header is
arbitrary, with the following exceptions:
- TX frames using an IP protocol (0x0800 or 0x86dd) will be dropped
- RX frames will have the protocol field set to ETH_P_802_3 (but will
not be properly formatted 802.3 frames)
@ -218,7 +226,7 @@ adding the dummy ethernet header on TX and stripping it on RX.
This is a simple example using tools commonly available, exporting
DssSessionId 5 as a pty character device pointed to by a /dev/nmea
symlink:
symlink::
ip link add link wwan0 name wwan0.dss5 type vlan id 261
ip link set dev wwan0.dss5 up
@ -236,7 +244,7 @@ map frames to the correct DSS session and adding 18 byte VLAN ethernet
headers with the appropriate tag on TX. In this case using a socket
filter is recommended, matching only the DSS VLAN subset. This avoid
unnecessary copying of unrelated IP session data to userspace. For
example:
example::
static struct sock_filter dssfilter[] = {
/* use special negative offsets to get VLAN tag */
@ -249,11 +257,11 @@ example:
BPF_JUMP(BPF_JMP|BPF_JGE|BPF_K, 512, 3, 0), /* 511 is last DSS VLAN */
/* verify ethertype */
BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 2 * ETH_ALEN),
BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, ETH_P_802_3, 0, 1),
BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 2 * ETH_ALEN),
BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, ETH_P_802_3, 0, 1),
BPF_STMT(BPF_RET|BPF_K, (u_int)-1), /* accept */
BPF_STMT(BPF_RET|BPF_K, 0), /* ignore */
BPF_STMT(BPF_RET|BPF_K, (u_int)-1), /* accept */
BPF_STMT(BPF_RET|BPF_K, 0), /* ignore */
};
@ -266,6 +274,7 @@ network device.
This mapping implies a few restrictions on multiplexed IPS and DSS
sessions, which may not always be practical:
- no IPS or DSS session can use a frame size greater than the MTU on
IP session 0
- no IPS or DSS session can be in the up state unless the network
@ -280,7 +289,7 @@ device.
Tip: It might be less confusing to the end user to name this VLAN
subdevice after the MBIM SessionID instead of the VLAN ID. For
example:
example::
ip link add link wwan0 name wwan0.0 type vlan id 4094
@ -290,7 +299,7 @@ VLAN mapping
Summarizing the cdc_mbim driver mapping described above, we have this
relationship between VLAN tags on the wwanY network device and MBIM
sessions on the shared USB data channel:
sessions on the shared USB data channel::
VLAN ID MBIM type MBIM SessionID Notes
---------------------------------------------------------
@ -310,30 +319,37 @@ sessions on the shared USB data channel:
References
==========
[1] USB Implementers Forum, Inc. - "Universal Serial Bus
Communications Class Subclass Specification for Mobile Broadband
Interface Model", Revision 1.0 (Errata 1), May 1, 2013
1) USB Implementers Forum, Inc. - "Universal Serial Bus
Communications Class Subclass Specification for Mobile Broadband
Interface Model", Revision 1.0 (Errata 1), May 1, 2013
- http://www.usb.org/developers/docs/devclass_docs/
[2] USB Implementers Forum, Inc. - "Universal Serial Bus
Communications Class Subclass Specifications for Network Control
Model Devices", Revision 1.0 (Errata 1), November 24, 2010
2) USB Implementers Forum, Inc. - "Universal Serial Bus
Communications Class Subclass Specifications for Network Control
Model Devices", Revision 1.0 (Errata 1), November 24, 2010
- http://www.usb.org/developers/docs/devclass_docs/
[3] libmbim - "a glib-based library for talking to WWAN modems and
devices which speak the Mobile Interface Broadband Model (MBIM)
protocol"
3) libmbim - "a glib-based library for talking to WWAN modems and
devices which speak the Mobile Interface Broadband Model (MBIM)
protocol"
- http://www.freedesktop.org/wiki/Software/libmbim/
[4] ModemManager - "a DBus-activated daemon which controls mobile
broadband (2G/3G/4G) devices and connections"
4) ModemManager - "a DBus-activated daemon which controls mobile
broadband (2G/3G/4G) devices and connections"
- http://www.freedesktop.org/wiki/Software/ModemManager/
[5] "MBIM (Mobile Broadband Interface Model) Registry"
5) "MBIM (Mobile Broadband Interface Model) Registry"
- http://compliance.usb.org/mbim/
[6] "/sys/kernel/debug/usb/devices output format"
6) "/sys/kernel/debug/usb/devices output format"
- Documentation/driver-api/usb/usb.rst
[7] "/sys/bus/usb/devices/.../descriptors"
7) "/sys/bus/usb/devices/.../descriptors"
- Documentation/ABI/stable/sysfs-bus-usb

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Documentation/networking/index.rst
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@ -45,6 +45,7 @@ Contents:
ax25
baycom
bonding
cdc_mbim
.. only:: subproject and html