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Diffstat (limited to 'Documentation/networking/device_drivers/cellular')
| -rw-r--r-- | Documentation/networking/device_drivers/cellular/index.rst | 18 | ||||
| -rw-r--r-- | Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst | 95 |
2 files changed, 113 insertions, 0 deletions
diff --git a/Documentation/networking/device_drivers/cellular/index.rst b/Documentation/networking/device_drivers/cellular/index.rst new file mode 100644 index 000000000..fc1812d3f --- /dev/null +++ b/Documentation/networking/device_drivers/cellular/index.rst @@ -0,0 +1,18 @@ +.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) + +Cellular Modem Device Drivers +============================= + +Contents: + +.. toctree:: + :maxdepth: 2 + + qualcomm/rmnet + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst b/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst new file mode 100644 index 000000000..70643b58d --- /dev/null +++ b/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst @@ -0,0 +1,95 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============ +Rmnet Driver +============ + +1. Introduction +=============== + +rmnet driver is used for supporting the Multiplexing and aggregation +Protocol (MAP). This protocol is used by all recent chipsets using Qualcomm +Technologies, Inc. modems. + +This driver can be used to register onto any physical network device in +IP mode. Physical transports include USB, HSIC, PCIe and IP accelerator. + +Multiplexing allows for creation of logical netdevices (rmnet devices) to +handle multiple private data networks (PDN) like a default internet, tethering, +multimedia messaging service (MMS) or IP media subsystem (IMS). Hardware sends +packets with MAP headers to rmnet. Based on the multiplexer id, rmnet +routes to the appropriate PDN after removing the MAP header. + +Aggregation is required to achieve high data rates. This involves hardware +sending aggregated bunch of MAP frames. rmnet driver will de-aggregate +these MAP frames and send them to appropriate PDN's. + +2. Packet format +================ + +a. MAP packet (data / control) + +MAP header has the same endianness of the IP packet. + +Packet format:: + + Bit 0 1 2-7 8 - 15 16 - 31 + Function Command / Data Reserved Pad Multiplexer ID Payload length + Bit 32 - x + Function Raw Bytes + +Command (1)/ Data (0) bit value is to indicate if the packet is a MAP command +or data packet. Control packet is used for transport level flow control. Data +packets are standard IP packets. + +Reserved bits are usually zeroed out and to be ignored by receiver. + +Padding is number of bytes to be added for 4 byte alignment if required by +hardware. + +Multiplexer ID is to indicate the PDN on which data has to be sent. + +Payload length includes the padding length but does not include MAP header +length. + +b. MAP packet (command specific):: + + Bit 0 1 2-7 8 - 15 16 - 31 + Function Command Reserved Pad Multiplexer ID Payload length + Bit 32 - 39 40 - 45 46 - 47 48 - 63 + Function Command name Reserved Command Type Reserved + Bit 64 - 95 + Function Transaction ID + Bit 96 - 127 + Function Command data + +Command 1 indicates disabling flow while 2 is enabling flow + +Command types + += ========================================== +0 for MAP command request +1 is to acknowledge the receipt of a command +2 is for unsupported commands +3 is for error during processing of commands += ========================================== + +c. Aggregation + +Aggregation is multiple MAP packets (can be data or command) delivered to +rmnet in a single linear skb. rmnet will process the individual +packets and either ACK the MAP command or deliver the IP packet to the +network stack as needed + +MAP header|IP Packet|Optional padding|MAP header|IP Packet|Optional padding.... + +MAP header|IP Packet|Optional padding|MAP header|Command Packet|Optional pad... + +3. Userspace configuration +========================== + +rmnet userspace configuration is done through netlink library librmnetctl +and command line utility rmnetcli. Utility is hosted in codeaurora forum git. +The driver uses rtnl_link_ops for communication. + +https://source.codeaurora.org/quic/la/platform/vendor/qcom-opensource/dataservices/tree/rmnetctl |