[PATCH net-next v2 1/3] docs: networking: Add documentation for MAPv5

[Sharath Chandra Vurukala]

Adding documentation explaining the new MAPv5 packet format
and the corresponding checksum offload header.

Signed-off-by: Sharath Chandra Vurukala <sharathv@xxxxxxxxxxxxxx>
---
 .../device_drivers/cellular/qualcomm/rmnet.rst     | 53 ++++++++++++++++++++--
 1 file changed, 49 insertions(+), 4 deletions(-)

diff --git a/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst b/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst
index 70643b5..8c81f19 100644
--- a/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst
+++ b/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst
@@ -27,7 +27,7 @@ these MAP frames and send them to appropriate PDN's.
 2. Packet format
 ================
 
-a. MAP packet (data / control)
+a. MAP packet v1 (data / control)
 
 MAP header has the same endianness of the IP packet.
 
@@ -35,8 +35,9 @@ 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
+
+  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
@@ -52,7 +53,51 @@ 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)::
+b. MAP packet v5 (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  Next Header  Pad   Multiplexer ID   Payload length
+
+  Bit            32 - 38        1               40              41-63
+  Function     Header Type    Next Header     Checksum Valid    Reserved
+
+  Bit            64-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.
+
+Next header is used to indicate the presence of another header, currently is
+limited to checksum header.
+
+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.
+
+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 are usually zeroed out and to be ignored by receiver.
+
+c. MAP packet v1/v5 (command specific)::
 
     Bit             0             1           2-7      8 - 15           16 - 31
     Function   Command         Reserved     Pad   Multiplexer ID    Payload length
-- 
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