Documentation: Update Phonet doc for Pipe Controller implementation

    or zero if encapsulation is off.

Phonet Pipe-controller Implementation

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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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