Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 182 insertions, 0 deletions

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+===============================
+IEEE 802.15.4 Developer's Guide
+===============================
+
+Introduction
+============
+The IEEE 802.15.4 working group focuses on standardization of the bottom
+two layers: Medium Access Control (MAC) and Physical access (PHY). And there
+are mainly two options available for upper layers:
+
+- ZigBee - proprietary protocol from the ZigBee Alliance
+- 6LoWPAN - IPv6 networking over low rate personal area networks
+
+The goal of the Linux-wpan is to provide a complete implementation
+of the IEEE 802.15.4 and 6LoWPAN protocols. IEEE 802.15.4 is a stack
+of protocols for organizing Low-Rate Wireless Personal Area Networks.
+
+The stack is composed of three main parts:
+
+- IEEE 802.15.4 layer;  We have chosen to use plain Berkeley socket API,
+  the generic Linux networking stack to transfer IEEE 802.15.4 data
+  messages and a special protocol over netlink for configuration/management
+- MAC - provides access to shared channel and reliable data delivery
+- PHY - represents device drivers
+
+Socket API
+==========
+
+::
+
+    int sd = socket(PF_IEEE802154, SOCK_DGRAM, 0);
+
+The address family, socket addresses etc. are defined in the
+include/net/af_ieee802154.h header or in the special header
+in the userspace package (see either https://linux-wpan.org/wpan-tools.html
+or the git tree at https://github.com/linux-wpan/wpan-tools).
+
+6LoWPAN Linux implementation
+============================
+
+The IEEE 802.15.4 standard specifies an MTU of 127 bytes, yielding about 80
+octets of actual MAC payload once security is turned on, on a wireless link
+with a link throughput of 250 kbps or less.  The 6LoWPAN adaptation format
+[RFC4944] was specified to carry IPv6 datagrams over such constrained links,
+taking into account limited bandwidth, memory, or energy resources that are
+expected in applications such as wireless Sensor Networks.  [RFC4944] defines
+a Mesh Addressing header to support sub-IP forwarding, a Fragmentation header
+to support the IPv6 minimum MTU requirement [RFC2460], and stateless header
+compression for IPv6 datagrams (LOWPAN_HC1 and LOWPAN_HC2) to reduce the
+relatively large IPv6 and UDP headers down to (in the best case) several bytes.
+
+In September 2011 the standard update was published - [RFC6282].
+It deprecates HC1 and HC2 compression and defines IPHC encoding format which is
+used in this Linux implementation.
+
+All the code related to 6lowpan you may find in files: net/6lowpan/*
+and net/ieee802154/6lowpan/*
+
+To setup a 6LoWPAN interface you need:
+1. Add IEEE802.15.4 interface and set channel and PAN ID;
+2. Add 6lowpan interface by command like:
+# ip link add link wpan0 name lowpan0 type lowpan
+3. Bring up 'lowpan0' interface
+
+Drivers
+=======
+
+Like with WiFi, there are several types of devices implementing IEEE 802.15.4.
+1) 'HardMAC'. The MAC layer is implemented in the device itself, the device
+exports a management (e.g. MLME) and data API.
+2) 'SoftMAC' or just radio. These types of devices are just radio transceivers
+possibly with some kinds of acceleration like automatic CRC computation and
+comparation, automagic ACK handling, address matching, etc.
+
+Those types of devices require different approach to be hooked into Linux kernel.
+
+HardMAC
+-------
+
+See the header include/net/ieee802154_netdev.h. You have to implement Linux
+net_device, with .type = ARPHRD_IEEE802154. Data is exchanged with socket family
+code via plain sk_buffs. On skb reception skb->cb must contain additional
+info as described in the struct ieee802154_mac_cb. During packet transmission
+the skb->cb is used to provide additional data to device's header_ops->create
+function. Be aware that this data can be overridden later (when socket code
+submits skb to qdisc), so if you need something from that cb later, you should
+store info in the skb->data on your own.
+
+To hook the MLME interface you have to populate the ml_priv field of your
+net_device with a pointer to struct ieee802154_mlme_ops instance. The fields
+assoc_req, assoc_resp, disassoc_req, start_req, and scan_req are optional.
+All other fields are required.
+
+SoftMAC
+-------
+
+The MAC is the middle layer in the IEEE 802.15.4 Linux stack. This moment it
+provides interface for drivers registration and management of slave interfaces.
+
+NOTE: Currently the only monitor device type is supported - it's IEEE 802.15.4
+stack interface for network sniffers (e.g. WireShark).
+
+This layer is going to be extended soon.
+
+See header include/net/mac802154.h and several drivers in
+drivers/net/ieee802154/.
+
+Fake drivers
+------------
+
+In addition there is a driver available which simulates a real device with
+SoftMAC (fakelb - IEEE 802.15.4 loopback driver) interface. This option
+provides a possibility to test and debug the stack without usage of real hardware.
+
+Device drivers API
+==================
+
+The include/net/mac802154.h defines following functions:
+
+.. c:function:: struct ieee802154_dev *ieee802154_alloc_device (size_t priv_size, struct ieee802154_ops *ops)
+
+Allocation of IEEE 802.15.4 compatible device.
+
+.. c:function:: void ieee802154_free_device(struct ieee802154_dev *dev)
+
+Freeing allocated device.
+
+.. c:function:: int ieee802154_register_device(struct ieee802154_dev *dev)
+
+Register PHY in the system.
+
+.. c:function:: void ieee802154_unregister_device(struct ieee802154_dev *dev)
+
+Freeing registered PHY.
+
+.. c:function:: void ieee802154_rx_irqsafe(struct ieee802154_hw *hw, struct sk_buff *skb, u8 lqi)
+
+Telling 802.15.4 module there is a new received frame in the skb with
+the RF Link Quality Indicator (LQI) from the hardware device.
+
+.. c:function:: void ieee802154_xmit_complete(struct ieee802154_hw *hw, struct sk_buff *skb, bool ifs_handling)
+
+Telling 802.15.4 module the frame in the skb is or going to be
+transmitted through the hardware device
+
+The device driver must implement the following callbacks in the IEEE 802.15.4
+operations structure at least::
+
+   struct ieee802154_ops {
+        ...
+        int     (*start)(struct ieee802154_hw *hw);
+        void    (*stop)(struct ieee802154_hw *hw);
+        ...
+        int     (*xmit_async)(struct ieee802154_hw *hw, struct sk_buff *skb);
+        int     (*ed)(struct ieee802154_hw *hw, u8 *level);
+        int     (*set_channel)(struct ieee802154_hw *hw, u8 page, u8 channel);
+        ...
+   };
+
+.. c:function:: int start(struct ieee802154_hw *hw)
+
+Handler that 802.15.4 module calls for the hardware device initialization.
+
+.. c:function:: void stop(struct ieee802154_hw *hw)
+
+Handler that 802.15.4 module calls for the hardware device cleanup.
+
+.. c:function:: int xmit_async(struct ieee802154_hw *hw, struct sk_buff *skb)
+
+Handler that 802.15.4 module calls for each frame in the skb going to be
+transmitted through the hardware device.
+
+.. c:function:: int ed(struct ieee802154_hw *hw, u8 *level)
+
+Handler that 802.15.4 module calls for Energy Detection from the hardware
+device.
+
+.. c:function:: int set_channel(struct ieee802154_hw *hw, u8 page, u8 channel)
+
+Set radio for listening on specific channel of the hardware device.
+
+Moreover IEEE 802.15.4 device operations structure should be filled.