irda (7)
Leading comments
Jean II - HPL - 03 irda.7
NAME
irda - The Linux-IrDA protocol stackSYNOPSIS
#include <linux/irda.h>stream_s = socket(PF_INET, SOCK_STREAM, 0);
seqpkt_s = socket(PF_INET, SOCK_SEQPACKET, 0);
dgram_s = socket(PF_INET, SOCK_DGRAM, IRDAPROTO_UNITDATA);
ultra_s = socket(PF_INET, SOCK_DGRAM, IRDAPROTO_ULTRA);
DESCRIPTION
Linux-IrDA is a complete implementation of the various IrDA protocols and IrDA drivers for Linux.The configuration of the low level of the IrDA stack (IrDA ports) and the various IrDA drivers are described in irattach(8).
The usage of the higher layers of the IrDA stack (IrCOMM, IrLPT, IrNET, IrLAN, OBEX...) are described in their respective man pages.
The core of the Linux-IrDA protocol stack is composed of the IrLAP, IrLMP, IrTTP and IrIAS protocols and is implemented as a kernel module. The programmer's interface for the IrDA stack is socket based. For more information on sockets, see socket(7).
Note that higher level IrDA protocols may offer a different programmer's interface. For example IrCOMM offers a TTY based interface and OBEX is available through a user space library.
SOCKETS TYPE
The Linux-IrDA socket interface offers 4 types of sockets:
- Stream socket - SOCK_STREAM, 0
-
Stream sockets provides a reliable, stream oriented, full duplex
connection between two sockets on top of
IrTTP,
similar to TCP sockets. IrTTP guarantees that the data arrives in
order and manages flow contol, IrLAP retransmits lost packets.
Stream sockets does not preserve record boundaries. - SeqPacket socket - SOCK_SEQPACKET, 0
-
SeqPacket sockets provides a reliable, datagram oriented, full duplex
connection between two sockets on top of
IrTTP.
IrTTP guarantees that the data arrives in order and manages flow
contol, IrLAP retransmits lost packets.
SeqPacket sockets preserve record boundaries. Large datagrams will be fragmented as needed. - Datagram socket - SOCK_DGRAM, IRDAPROTO_UNITDATA
-
SeqPacket sockets provides a reliable, datagram oriented, full duplex
connection between two sockets on top of
IrLMP.
There is no guarantees that the data arrives in order and there is no
flow contol, however IrLAP retransmits lost packets.
Datagram sockets preserve record boundaries. No fragmentation is provided, datagrams larger than the IrDA link MTU are truncated or discarded. - Ultra socket - SOCK_DGRAM, IRDAPROTO_ULTRA
-
Ultra sockets provides a connectionless, unreliable datagram packet
service on top of
IrLAP-Ultra.
Ultra datagrams are sent and receive only when no IrLAP connection is
established and otherwise discarded. They are always transmitted at
9600 bauds. Datagrams may be lost, reordered, and there is no flow
control.
Ultra sockets preserve record boundaries. No fragmentation is provided, datagrams larger than the Ultra MTU (382 bytes) are truncated or discarded.
ADDRESS FORMAT
An IrDA socket address is defined as a combination of an IrDA interface address and a service name. Service names are automatically resolved to lsap through the IrIAP protocol.
struct sockaddr_irda {
sa_family_t sir_family; /* AF_IRDA */
__u8 sir_lsap_sel; /* LSAP selector */
__u32 sir_addr; /* Device address */
char sir_name[25]; /* Usually <service>:IrDA:TinyTP */
};
sin_family is always set to AF_IRDA. sir_lsap_sel is usually not used. sir_addr is the address of the peer and optional (and that case the first peer discoverd will be used). sir_name is the service name of the socket.
SOCKET OPTIONS
IrDA sockets supports some protocol specific socket options that can be set with setsockopt(2) and read with getsockopt(2). The socket option level for IrDA is SOL_IRLMP.Options that can be set:
- IRLMP_IAS_SET
- Set an entry in the local IAS database.
- IRLMP_IAS_DEL
- Delete an entry from the local IAS database.
- IRLMP_MAX_SDU_SIZE
- Set maximum receive MTU for SeqPacket sockets.
- IRLMP_HINTS_SET
- Set IrDA hint bits to be advertised to peers.
- IRLMP_HINT_MASK_SET
- Set IrDA hint bits filter to be used when performing discovery.
Options that can be get:
- IRLMP_ENUMDEVICES
- Perform link level discovery and return the content of the discovery log.
- IRLMP_MAX_SDU_SIZE
- Get maximum receive MTU.
- IRLMP_IAS_GET
- Get an entry from the local IAS database.
- IRLMP_IAS_QUERY
- Query an entry in IAS database of a peer using IrIAP.
- IRLMP_WAITDEVICE
- Block until a new device is discovered. Experimental feature, use with caution.