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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 000000000000..4118384cf8eb --- /dev/null +++ b/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst @@ -0,0 +1,197 @@ +.. 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 v1 (data / control) + +MAP header fields are in big endian format. + +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. Command packet is used for transport level flow control. Data +packets are standard IP packets. + +Reserved bits must be zero when sent and ignored when received. + +Padding is the number of bytes to be appended to the payload to +ensure 4 byte alignment. + +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 v4 (data / control) + +MAP header fields are in big endian format. + +Packet format:: + + Bit 0 1 2-7 8-15 16-31 + Function Command / Data Reserved Pad Multiplexer ID Payload length + + Bit 32-(x-33) (x-32)-x + Function Raw bytes Checksum offload header + +Command (1)/ Data (0) bit value is to indicate if the packet is a MAP command +or data packet. Command packet is used for transport level flow control. Data +packets are standard IP packets. + +Reserved bits must be zero when sent and ignored when received. + +Padding is the number of bytes to be appended to the payload to +ensure 4 byte alignment. + +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. + +Checksum offload header, has the information about the checksum processing done +by the hardware.Checksum offload header fields are in big endian format. + +Packet format:: + + Bit 0-14 15 16-31 + Function Reserved Valid Checksum start offset + + Bit 31-47 48-64 + Function Checksum length Checksum value + +Reserved bits must be zero when sent and ignored when received. + +Valid bit indicates whether the partial checksum is calculated and is valid. +Set to 1, if its is valid. Set to 0 otherwise. + +Padding is the number of bytes to be appended to the payload to +ensure 4 byte alignment. + +Checksum start offset, Indicates the offset in bytes from the beginning of the +IP header, from which modem computed checksum. + +Checksum length is the Length in bytes starting from CKSUM_START_OFFSET, +over which checksum is computed. + +Checksum value, indicates the checksum computed. + +c. MAP packet v5 (data / control) + +MAP header fields are in big endian format. + +Packet format:: + + Bit 0 1 2-7 8-15 16-31 + Function Command / Data Next header 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. Command packet is used for transport level flow control. Data +packets are standard IP packets. + +Next header is used to indicate the presence of another header, currently is +limited to checksum header. + +Padding is the number of bytes to be appended to the payload to +ensure 4 byte alignment. + +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. + +d. Checksum offload header v5 + +Checksum offload header fields are in big endian format. + + Bit 0 - 6 7 8-15 16-31 + Function Header Type Next Header Checksum Valid Reserved + +Header Type is to indicate the type of header, this usually is set to CHECKSUM + +Header types += ========================================== +0 Reserved +1 Reserved +2 checksum header + +Checksum Valid is to indicate whether the header checksum is valid. Value of 1 +implies that checksum is calculated on this packet and is valid, value of 0 +indicates that the calculated packet checksum is invalid. + +Reserved bits must be zero when sent and ignored when received. + +e. MAP packet v1/v5 (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 += ========================================== + +f. 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 |