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-rw-r--r--Documentation/networking/can.txt44
-rw-r--r--Documentation/networking/phonet.txt175
2 files changed, 215 insertions, 4 deletions
diff --git a/Documentation/networking/can.txt b/Documentation/networking/can.txt
index 297ba7b1ccaf..2035bc4932f2 100644
--- a/Documentation/networking/can.txt
+++ b/Documentation/networking/can.txt
@@ -35,8 +35,9 @@ This file contains
35 6.1 general settings 35 6.1 general settings
36 6.2 local loopback of sent frames 36 6.2 local loopback of sent frames
37 6.3 CAN controller hardware filters 37 6.3 CAN controller hardware filters
38 6.4 currently supported CAN hardware 38 6.4 The virtual CAN driver (vcan)
39 6.5 todo 39 6.5 currently supported CAN hardware
40 6.6 todo
40 41
41 7 Credits 42 7 Credits
42 43
@@ -584,7 +585,42 @@ solution for a couple of reasons:
584 @133MHz with four SJA1000 CAN controllers from 2002 under heavy bus 585 @133MHz with four SJA1000 CAN controllers from 2002 under heavy bus
585 load without any problems ... 586 load without any problems ...
586 587
587 6.4 currently supported CAN hardware (September 2007) 588 6.4 The virtual CAN driver (vcan)
589
590 Similar to the network loopback devices, vcan offers a virtual local
591 CAN interface. A full qualified address on CAN consists of
592
593 - a unique CAN Identifier (CAN ID)
594 - the CAN bus this CAN ID is transmitted on (e.g. can0)
595
596 so in common use cases more than one virtual CAN interface is needed.
597
598 The virtual CAN interfaces allow the transmission and reception of CAN
599 frames without real CAN controller hardware. Virtual CAN network
600 devices are usually named 'vcanX', like vcan0 vcan1 vcan2 ...
601 When compiled as a module the virtual CAN driver module is called vcan.ko
602
603 Since Linux Kernel version 2.6.24 the vcan driver supports the Kernel
604 netlink interface to create vcan network devices. The creation and
605 removal of vcan network devices can be managed with the ip(8) tool:
606
607 - Create a virtual CAN network interface:
608 ip link add type vcan
609
610 - Create a virtual CAN network interface with a specific name 'vcan42':
611 ip link add dev vcan42 type vcan
612
613 - Remove a (virtual CAN) network interface 'vcan42':
614 ip link del vcan42
615
616 The tool 'vcan' from the SocketCAN SVN repository on BerliOS is obsolete.
617
618 Virtual CAN network device creation in older Kernels:
619 In Linux Kernel versions < 2.6.24 the vcan driver creates 4 vcan
620 netdevices at module load time by default. This value can be changed
621 with the module parameter 'numdev'. E.g. 'modprobe vcan numdev=8'
622
623 6.5 currently supported CAN hardware
588 624
589 On the project website http://developer.berlios.de/projects/socketcan 625 On the project website http://developer.berlios.de/projects/socketcan
590 there are different drivers available: 626 there are different drivers available:
@@ -603,7 +639,7 @@ solution for a couple of reasons:
603 639
604 Please check the Mailing Lists on the berlios OSS project website. 640 Please check the Mailing Lists on the berlios OSS project website.
605 641
606 6.5 todo (September 2007) 642 6.6 todo
607 643
608 The configuration interface for CAN network drivers is still an open 644 The configuration interface for CAN network drivers is still an open
609 issue that has not been finalized in the socketcan project. Also the 645 issue that has not been finalized in the socketcan project. Also the
diff --git a/Documentation/networking/phonet.txt b/Documentation/networking/phonet.txt
new file mode 100644
index 000000000000..0e6e592f4f55
--- /dev/null
+++ b/Documentation/networking/phonet.txt
@@ -0,0 +1,175 @@
1Linux Phonet protocol family
2============================
3
4Introduction
5------------
6
7Phonet is a packet protocol used by Nokia cellular modems for both IPC
8and RPC. With the Linux Phonet socket family, Linux host processes can
9receive and send messages from/to the modem, or any other external
10device attached to the modem. The modem takes care of routing.
11
12Phonet packets can be exchanged through various hardware connections
13depending on the device, such as:
14 - USB with the CDC Phonet interface,
15 - infrared,
16 - Bluetooth,
17 - an RS232 serial port (with a dedicated "FBUS" line discipline),
18 - the SSI bus with some TI OMAP processors.
19
20
21Packets format
22--------------
23
24Phonet packets have a common header as follows:
25
26 struct phonethdr {
27 uint8_t pn_media; /* Media type (link-layer identifier) */
28 uint8_t pn_rdev; /* Receiver device ID */
29 uint8_t pn_sdev; /* Sender device ID */
30 uint8_t pn_res; /* Resource ID or function */
31 uint16_t pn_length; /* Big-endian message byte length (minus 6) */
32 uint8_t pn_robj; /* Receiver object ID */
33 uint8_t pn_sobj; /* Sender object ID */
34 };
35
36On Linux, the link-layer header includes the pn_media byte (see below).
37The next 7 bytes are part of the network-layer header.
38
39The device ID is split: the 6 higher-order bits consitute the device
40address, while the 2 lower-order bits are used for multiplexing, as are
41the 8-bit object identifiers. As such, Phonet can be considered as a
42network layer with 6 bits of address space and 10 bits for transport
43protocol (much like port numbers in IP world).
44
45The modem always has address number zero. All other device have a their
46own 6-bit address.
47
48
49Link layer
50----------
51
52Phonet links are always point-to-point links. The link layer header
53consists of a single Phonet media type byte. It uniquely identifies the
54link through which the packet is transmitted, from the modem's
55perspective. Each Phonet network device shall prepend and set the media
56type byte as appropriate. For convenience, a common phonet_header_ops
57link-layer header operations structure is provided. It sets the
58media type according to the network device hardware address.
59
60Linux Phonet network interfaces support a dedicated link layer packets
61type (ETH_P_PHONET) which is out of the Ethernet type range. They can
62only send and receive Phonet packets.
63
64The virtual TUN tunnel device driver can also be used for Phonet. This
65requires IFF_TUN mode, _without_ the IFF_NO_PI flag. In this case,
66there is no link-layer header, so there is no Phonet media type byte.
67
68Note that Phonet interfaces are not allowed to re-order packets, so
69only the (default) Linux FIFO qdisc should be used with them.
70
71
72Network layer
73-------------
74
75The Phonet socket address family maps the Phonet packet header:
76
77 struct sockaddr_pn {
78 sa_family_t spn_family; /* AF_PHONET */
79 uint8_t spn_obj; /* Object ID */
80 uint8_t spn_dev; /* Device ID */
81 uint8_t spn_resource; /* Resource or function */
82 uint8_t spn_zero[...]; /* Padding */
83 };
84
85The resource field is only used when sending and receiving;
86It is ignored by bind() and getsockname().
87
88
89Low-level datagram protocol
90---------------------------
91
92Applications can send Phonet messages using the Phonet datagram socket
93protocol from the PF_PHONET family. Each socket is bound to one of the
942^10 object IDs available, and can send and receive packets with any
95other peer.
96
97 struct sockaddr_pn addr = { .spn_family = AF_PHONET, };
98 ssize_t len;
99 socklen_t addrlen = sizeof(addr);
100 int fd;
101
102 fd = socket(PF_PHONET, SOCK_DGRAM, 0);
103 bind(fd, (struct sockaddr *)&addr, sizeof(addr));
104 /* ... */
105
106 sendto(fd, msg, msglen, 0, (struct sockaddr *)&addr, sizeof(addr));
107 len = recvfrom(fd, buf, sizeof(buf), 0,
108 (struct sockaddr *)&addr, &addrlen);
109
110This protocol follows the SOCK_DGRAM connection-less semantics.
111However, connect() and getpeername() are not supported, as they did
112not seem useful with Phonet usages (could be added easily).
113
114
115Phonet Pipe protocol
116--------------------
117
118The Phonet Pipe protocol is a simple sequenced packets protocol
119with end-to-end congestion control. It uses the passive listening
120socket paradigm. The listening socket is bound to an unique free object
121ID. Each listening socket can handle up to 255 simultaneous
122connections, one per accept()'d socket.
123
124 int lfd, cfd;
125
126 lfd = socket(PF_PHONET, SOCK_SEQPACKET, PN_PROTO_PIPE);
127 listen (lfd, INT_MAX);
128
129 /* ... */
130 cfd = accept(lfd, NULL, NULL);
131 for (;;)
132 {
133 char buf[...];
134 ssize_t len = read(cfd, buf, sizeof(buf));
135
136 /* ... */
137
138 write(cfd, msg, msglen);
139 }
140
141Connections are established between two endpoints by a "third party"
142application. This means that both endpoints are passive; so connect()
143is not possible.
144
145WARNING:
146When polling a connected pipe socket for writability, there is an
147intrinsic race condition whereby writability might be lost between the
148polling and the writing system calls. In this case, the socket will
149block until write because possible again, unless non-blocking mode
150becomes enabled.
151
152
153The pipe protocol provides two socket options at the SOL_PNPIPE level:
154
155 PNPIPE_ENCAP accepts one integer value (int) of:
156
157 PNPIPE_ENCAP_NONE: The socket operates normally (default).
158
159 PNPIPE_ENCAP_IP: The socket is used as a backend for a virtual IP
160 interface. This requires CAP_NET_ADMIN capability. GPRS data
161 support on Nokia modems can use this. Note that the socket cannot
162 be reliably poll()'d or read() from while in this mode.
163
164 PNPIPE_IFINDEX is a read-only integer value. It contains the
165 interface index of the network interface created by PNPIPE_ENCAP,
166 or zero if encapsulation is off.
167
168
169Authors
170-------
171
172Linux Phonet was initially written by Sakari Ailus.
173Other contributors include Mikä Liljeberg, Andras Domokos,
174Carlos Chinea and Rémi Denis-Courmont.
175Copyright (C) 2008 Nokia Corporation.
generated by cgit v1.2.2 (git 2.25.0) at 2025-03-11 21:03:02 -0400