Re: [PATCH net-next-2.6 12/13] net-caif: add CAIF documentation

From: Sjur Braendeland <redacted>

Documentation of the CAIF Protocol.

Signed-off-by: Sjur Braendeland <redacted>
---
 Documentation/networking/caif/Linux-CAIF.txt |  235 ++++++++++++++++++++++++++
 Documentation/networking/caif/README         |   27 +++
 2 files changed, 262 insertions(+), 0 deletions(-)

diff --git a/Documentation/networking/caif/Linux-CAIF.txt b/Documentation/networking/caif/Linux-CAIF.txt
new file mode 100644
index 0000000..5576e42
--- /dev/null
+++ b/Documentation/networking/caif/Linux-CAIF.txt

@@ -0,0 +1,235 @@
+Linux CAIF
+===========
+copyright (C) ST-Ericsson AB 2010
+Author: Sjur Brendeland/ sjur.brandeland@stericsson.com
+License terms: GNU General Public License (GPL) version 2
+
+
+Introduction
+------------
+CAIF is a MUX protocol used by ST-Ericsson cellular modems for
+communication between Modem and host. The host processes can open virtual AT
+channels, initiate GPRS Data connections, Video channels and Utility Channels.
+The Utility Channels are general purpose pipes between modem and host.
+
+ST-Ericsson modems support a number of transports between modem
+and host. Currently, UART and Loopback are available for Linux.
+
+
+Architecture:
+------------
+The implementation of CAIF is divided into:
+* CAIF Socket Layer, Kernel API, and  Net Device.
+* CAIF Generic Protocol Implementation
+* CAIF Link Layer, implemented as NET devices.
+
+
+  RTNL/IOCTL
+   !
+   !	 +------+   +------+   +------+
+   !	+------+!  +------+!  +------+!
+   !	! Sock !!  !Kernel!!  ! Net  !!
+   !	! API  !+  ! API  !+  ! Dev  !+	  <- CAIF Client APIs
+   !	+------+   +------!   +------+
+   !	   !	      !		 !
+   !	   +----------!----------+
+   !		   +------+		  <- CAIF Protocol Implementation
+   +------->	   ! CAIF !
+		   +------+
+	     +--------!--------+
+	     !		       !
+	  +------+	    +-----+
+	  !Loop	 !	    ! TTY !	  <- Link Layer (Net Devices)
+	  +------+	    +-----+
+
+
+Using CAIF (IP) Net Device
+----------------------
+CAIF Net device can be created by use of Socket IOCTLs,
+or RT Netlink.
+
+  static struct ifcaif_param param = {
+    .ipv4_connid = 1,
+    .loop = 0
+  };
+  static struct ifreq ifr = {
+    .ifr_name = "caif%d",
+    .ifr_ifru.ifru_data = &param
+
+  };
+  s = socket(AF_CAIF, SOCK_SEQPACKET, CAIFPROTO_AT);
+  ioctl(s, SIOCCAIFNETNEW, &ifr);
+
+
+Using the Kernel API
+----------------------
+The Kernel API is used for accessing CAIF channels from the
+kernel.
+The user of the API has to implement two callbacks for receive
+and control.
+The receive callback gives a CAIF packet as a SKB. The control
+callback will
+notify of channel initialization complete, and flow-on/flow-
+off.
+
+
+  struct caif_device caif_dev = {
+    .caif_config = {
+     .name = "MYDEV"
+     .type = CAIF_CHTY_AT
+    }
+   .receive_cb = my_receive,
+   .control_cb = my_control,
+  };
+  caif_add_device(&caif_dev);
+  caif_transmit(&caif_dev, skb);
+
+See the caif_kernel.h for details about the CAIF kernel API.
+
+
+I M P L E M E N T A T I O N
+===========================
+===========================
+
+Generic CAIF Protocol Layer
+=========================================
+
+caif/generic is a generic CAIF protocol implementation. It implements the CAIF
+protocol as defined by ST-Ericsson.
+It implements the CAIF protocol stack in a layered approach, where
+each layer described in the specification is implemented as a separate layer.
+The architecture is inspired by the design patterns "Protocol Layer" and
+"Protocol Packet".
+
+== CAIF structure ==
+
+The goal is to have generic CAIF as OS and system independent as possible.
+All generic CAIF code can be found under net/caif/generic and
+include/net/caif/generic.
+
+The generic CAIF implementation is:
+      -	Simple implementation of CAIF.
+      -	Layered architecture (a la Streams), each layer in the CAIF
+	specification is implemented in a separate c-file.
+      -	Clients must implement PHY layer to access physical HW
+	with receive and transmit functions.
+      -	Clients must call configuration function to add PHY layer.
+      -	Clients must implement adaptation layer to consume/produce
+	CAIF payload with receive and transmit functions.
+      -	Clients must call configuration function to add adaptation
+	layer.
+      - When receiving / transmitting CAIF Packets (cfpkt), ownership is passed
+	to the called function (except for framing layers' receive functions
+	or if a transmit function returns an error, in which case the caller
+	must free the packet).
+
+Layered Architecture
+--------------------
+The CAIF protocol can be divided into two parts: Support functions and Protocol
+Implementation. The support functions include:
+
+      - CFPKT CAIF Packet. Implementation of CAIF Protocol Packet. The
+	CAIF Packet has functions for creating, destroying and adding content
+	and for adding/extracting header and trailers to protocol packets.
+
+      - CFLST CAIF list implementation.
+
+      - CFGLUE CAIF Glue. Contains OS Specifics, such as memory
+	allocation, endianness, etc.
+
+The CAIF Protocol implementation contains:
+
+      - CFCNFG CAIF Configuration layer. Configures the CAIF Protocol
+	Stack and has a Client interface for adding Link-Layer and
+	Driver interfaces on top of the CAIF Stack.
+
+      - CFCTRL CAIF Control layer. Encodes and Decodes control messages
+	such as enumeration and channel setup. Also matches request and
+	response messages.
+
+      - CFSERVL General CAIF Service Layer functionality; handles flow
+	control and remote shutdown requests.
+
+      - CFVEI CAIF VEI layer. Handles CAIF VEI layer (AT-Channel),
+	encodes/decodes VEI frames.
+