Project

General

Profile

QMI

QMI (Qualcomm MSM Interface)

This is the general term for all related messaging between processors and their software stacks on Qualcomm cellular processors.

In case of data cards / data modems, QMI is often exposed to the host PC via USB. On Linux hosts, the open source libqmi-glib (https://www.freedesktop.org/wiki/Software/libqmi/) is often used to inplement the QMI protocols to control the cellular modem.

QMI offers various different services (e.g. WDS, the wireless data service) which are exposed via the QMI protocol stack on one or many QMI ports.

In the context of multi-processor Qualcomm chipsets, such as the MDM9615/9x07 used in cellular modems / data cards, or also in the case of Android smartphones, QMI ports are exposed to the Linux-running application CPU core inside the chip. There can be many different transport mechanisms, but in the case of modern integrated chips, it is primarily SMD (Shared Memory Device).

On the OE based Linux in the cellular modems, there is a proprietary QMI multiplex daemon (qmuxd), which acts as a proxy between the shared memory device and various userspace processes accessing QMI services. Those client programs communicate with qmuxd over a unix-domain socket. There are (proprietary) libraries (libqmi.so, libqmi-framework.so) that encapsulate the qmuxd and QMI communication protocols, the message encoding/decoding and state machines.

On Android phones using integrated Qualcomm chipsets, there is an Android RIL daemon that converts from RIL to QMI.

IDL

  • int32_t qmi_idl_get_service_id(service_obj, service_id)
    get service ID for a given service object
  • qmi_idl_message_decode()
    Decode from TLV to C structure
  • qmi_idl_message_encode()
    Encode from C structure to wire format TLV

IDL Structures

Individual services are implemented in a data-driven manner by data
structures describing the type of messsages and the message TLV
structure.

In the end, a service describes itself using the master structure
qmi_idl_service_object, consisting of
  • library version (0x04)
  • idl version
  • service ID
  • maximum message length
  • number of command/response/indication messges in tables
  • tables describing messages (qmi_idl_service_message_table_entry)
  • tables describing types (qmi_idl_type_table_object)

The data structures describing a given service are generated by an IDL
compiler.

If you have a binary libqmi* providing IDL definitions, you can use the following
commadn to extract the IDL service definitions supported:

strings libqmi* | grep _idl_service_object | sort | uniq

CSI (Common Service Interface)

Data model (see qmi_csi_common.h for more info):

  • each service list has a list of active services
  • each service has a table of transports associated with it
  • each service also has a list of connected clients
  • each client has a pointer to the transport it connected from
  • each client also has a list of outstanding transactions

CSI has only a single transport on Linux, using te AF_MSM_IPC type
sockets as a basis.

SAP (Service Access Proxy)

Intended to export a service off-chip using QMUX daemon.

Encodes/Decodes messages for registering services:
  • register_service request/response
  • deregister_service request/response
  • client_connect indication
  • client_disconnect indication

QMUX (QMI Multiplex)

The related code can either talk directly to the shared-memory devices
on Linux and thus the hardware (see qmi_platform_qmux_io.c).

It can however also establish a connection via a multiplex daemon.
This connection utilizes unix domain STREAM type sockets in
/dev/socket, specifically:
  • /dev/socket/qmux_audio/qmux_{client,connect}_socket
  • /dev/socket/qmux_bluetooth/qmux_{client,connect}_socket
  • /dev/socket/qmux_radio/qmux_{client,connect}_socket
  • /dev/socket/qmux_gps/qmux_{client,connect}_socket
  • /var/qmux_{client,connect}_socket on non-android devices

QCCI (QMI Common Client Interface)

The QCCI layer wraps QMI into the respective transport. The
transports supported are:

  • IPC router (linux kernel socket family)
  • QMUXD (using qmi_qmux_... API, via unix domain sockets)
  • UDP packets (base port 10000)

The CCI API is what QMI clients normally would call to initiate a
client connection to a service. The CCI functions would then normally
be wrapped by some service specific code that wraps the IDL
definitions for message encoding/decoding and provides
service-specific API to the client.

AT command implementation (QMI ATCOP service layer)

This is used by client programs to register AT command call-backs within the modems AT command interpreter.

The QMI ATCOP service layer seems to be pre-IDL, as it doesn't have the usual IDL compiler code structure.

The baseband firmware appears have a compile-time white-list of AT commands for which the AT command forwarding is permitted. Any other commands are rejected with error 48 (invalid argument)

Qualcomm default seems to permit +CLVL, +CKPD, +CMUT, +CTSA, +CBKLT, +CFUN, +CDIS, +CRSL, +CMAR, +CSO, +CSS, +CBC, $QCPWRDN and this may be extended by vendor-specific commands, such as +QFOTADL in the Quectel case

qmi_atcop_fwd_at_urc_req()

used to send unsolicited response codes to modem

qmi_atcop_fwd_at_cmd_resp()

used by client to send response to an AT command previously forwarded
to the client from the modem

qmi_atcop_reg_at_command_fwd_req()

used by client to registre any AT commands that need to be forwarded
to it from the modem

qmi_atcop_srvc_init_client()

intialization

qmi_atcop_srvc_release_client()

cleanup

QMI Services (via IDL)

See EC20_QMI and EC25_QMI for the IDLs included in the respective modem firmware

Test Service

Part of qmi-framework. IDL descriptions for

  • ping req/resp
  • test_ind
  • data req/resp
  • large_data req/resp
  • data_ind_reg req/resp
  • test_data_ind
  • get_service_name req/resp

common_v01

  • get_supported_msgs req/resp
  • get_supported_fields req/resp

application_traffic_pairing_v01

card_application_toolkit_v02

SIM/USIM toolkit related

circuit_switched_video_telephony_v01

coexistence_manager_v01

bt/wifi coexistance?

control_service_v01

data_system_determination_v01

check for availability of wlan/modem/... data bearers and set related
policy

device_management_service_v01

  • inquiry about device maker/model/version
  • MSISDN, ICCID, IMSI, MAC address inquiry
  • PIN entry/management
  • locking

ip_multimedia_subsystem_application_v01

ip_multimedia_subsystem_dcm_v01

ip_multimedia_subsystem_presence_v01

ip_multimedia_subsystem_rtp_v01

ip_multimedia_subsystem_settings_v01

ip_multimedia_subsystem_video_telephony_v01

network_access_service_common_v01

network_access_service_v01

  • network scan / registration
  • network preference
  • forbidden networks
  • rf band information
  • operator name
  • rx diversity

persistent_device_configuration_v01

phonebook_manager_service_v01

qmi_adc_service_v01

  • ADC conversion/calibration

qmi_ims_vt_v01

qualcomm_mobile_access_point_msgr_v01

qualcomm_mobile_access_point_v01

See QCMAP

radio_frequency_radiated_performance_enhancement_v01

sar_vs_service_v01

specific_absorption_rate_v01

user_identity_module_remote_v01

APDU forwarding of SIM/USIM to remote location?

Probably more te opposite: A way how a modem can export a CCID device
towards a PC and then map the APDUs in something that the modem can
digest?

user_identity_module_v01

SIM/USIM card access

  • read/write transparent / record EF
  • verify / unblock / change pin
  • card power up/down
  • authenticate
  • raw APDU
  • SAP
  • logicla channels
  • ATR
  • multi sim (slot) management

voice_service_common_v02

voice_service_v02

call control

wireless_data_administrative_service_v01

wireless_data_service_v01

cellular data

wireless_messaging_service_v01

SMS-PP, SMS-CB

further reading

http://www.lanedo.com/documents/Qualcomm%20Gobi%20devices%20on%20Linux.pdf
File has since been removed. After extracting it from Archive.org it has been attached here.

Add picture from clipboard (Maximum size: 48.8 MB)