+++ /dev/null
-
- Linux IEEE 802.15.4 implementation
-
-
-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 http://wpan.cakelab.org/ or the
-git tree at https://github.com/linux-wpan/wpan-tools).
-
-
-Kernel side
-=============
-
-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/.
-
-
-Device drivers API
-==================
-
-The include/net/mac802154.h defines following functions:
- - struct ieee802154_hw *
- ieee802154_alloc_hw(size_t priv_data_len, const struct ieee802154_ops *ops):
- allocation of IEEE 802.15.4 compatible hardware device
-
- - void ieee802154_free_hw(struct ieee802154_hw *hw):
- freeing allocated hardware device
-
- - int ieee802154_register_hw(struct ieee802154_hw *hw):
- register PHY which is the allocated hardware device, in the system
-
- - void ieee802154_unregister_hw(struct ieee802154_hw *hw):
- freeing registered PHY
-
- - 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
-
- - 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);
- ...
-};
-
- - int start(struct ieee802154_hw *hw):
- handler that 802.15.4 module calls for the hardware device initialization.
-
- - void stop(struct ieee802154_hw *hw):
- handler that 802.15.4 module calls for the hardware device cleanup.
-
- - 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.
-
- - int ed(struct ieee802154_hw *hw, u8 *level):
- handler that 802.15.4 module calls for Energy Detection from the hardware
- device.
-
- - 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.
-
-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.
-
-See sources in drivers/net/ieee802154 folder for more details.
-
-
-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
projects / mirror_ubuntu-kernels.git / commitdiff