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diff --git a/Documentation/networking/phonet.txt b/Documentation/networking/phonet.txt
index cf76608a2d35..cccf5ff07ec2 100644
--- a/Documentation/networking/phonet.txt
+++ b/Documentation/networking/phonet.txt
@@ -182,6 +182,59 @@ The pipe protocol provides two socket options at the SOL_PNPIPE level:
or zero if encapsulation is off.
+Phonet Pipe-controller Implementation
+-------------------------------------
+
+Phonet Pipe-controller is enabled by selecting the CONFIG_PHONET_PIPECTRLR Kconfig
+option. It is useful when communicating with those Nokia Modems which do not
+implement Pipe controller in them e.g. Nokia Slim Modem used in ST-Ericsson
+U8500 platform.
+
+The implementation is based on the Data Connection Establishment Sequence
+depicted in 'Nokia Wireless Modem API - Wireless_modem_user_guide.pdf'
+document.
+
+It allows a phonet sequenced socket (host-pep) to initiate a Pipe connection
+between itself and a remote pipe-end point (e.g. modem).
+
+The implementation adds socket options at SOL_PNPIPE level:
+
+ PNPIPE_CREATE
+ It accepts an integer argument where-in
+ lower order 16 bits: pn_dev and pn_port pair for remote pep.
+ higher order 16 bits: 8 bit pipe-handle
+
+ It sends a PNS_PEP_CONNECT_REQ on sequenced socket itself. On getting
+ PNS_PEP_CONNECT_RESP, it sends PNS_PEP_CONNECT_REQ to remote pep. On
+ getting response from remote pep, it selects the best possible Flow
+ control mechanism supported by remote-pep (modem) and then it sends
+ PNS_PEP_CREATED_IND to the sequenced socket and to the remote pep.
+
+ It then updates the pipe state associated with the sequenced socket to
+ be PIPE_DISABLED.
+
+ PNPIPE_ENABLE
+ It follows the same sequence as above for enabling a pipe by sending
+ PNS_PEP_ENABLE_REQ initially and then sending PNS_PEP_ENABLED_IND after
+ getting responses from sequenced socket and remote-pep.
+ It will also update the pipe state associated with the sequenced socket
+ to PIPE_ENABLED.
+
+ PNPIPE_DESTROY
+ This will send out PNS_PEP_DISCONNECT_REQ on the sequenced socket and
+ the remote pep.
+ It will also update the pipe state associated with the sequenced socket
+ to PIPE_IDLE
+
+ PNPIPE_INQ
+ This getsocktopt allows the user-space running on the sequenced socket
+ to examine the pipe state associated with that socket ie. whether the
+ pipe is created (PIPE_DISABLED) or enabled (PIPE_ENABLED) or disabled
+ (PIPE_DISABLED) or no pipe exists (PIPE_IDLE).
+
+After a pipe has been created and enabled successfully, the Pipe data can be
+exchanged between the host-pep and remote-pep (modem).
+
Authors
-------
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