Documentation/networking/phonet.rst

1 .. SPDX-License-Identifier: GPL-2.0
5 Linux Phonet protocol family
9 ------------
11 Phonet is a packet protocol used by Nokia cellular modems for both IPC
19   - USB with the CDC Phonet interface,
20   - infrared,
21   - Bluetooth,
22   - an RS232 serial port (with a dedicated "FBUS" line discipline),
23   - the SSI bus with some TI OMAP processors.
27 --------------
32     uint8_t  pn_media;  /* Media type (link-layer identifier) */
33     uint8_t  pn_rdev;   /* Receiver device ID */
34     uint8_t  pn_sdev;   /* Sender device ID */
35     uint8_t  pn_res;    /* Resource ID or function */
36     uint16_t pn_length; /* Big-endian message byte length (minus 6) */
37     uint8_t  pn_robj;   /* Receiver object ID */
38     uint8_t  pn_sobj;   /* Sender object ID */
41 On Linux, the link-layer header includes the pn_media byte (see below).
42 The next 7 bytes are part of the network-layer header.
44 The device ID is split: the 6 higher-order bits constitute the device
45 address, while the 2 lower-order bits are used for multiplexing, as are
46 the 8-bit object identifiers. As such, Phonet can be considered as a
48 protocol (much like port numbers in IP world).
51 own 6-bit address.
55 ----------
57 Phonet links are always point-to-point links. The link layer header
62 link-layer header operations structure is provided. It sets the
71 there is no link-layer header, so there is no Phonet media type byte.
73 Note that Phonet interfaces are not allowed to re-order packets, so
78 -------------
84     uint8_t     spn_obj;       /* Object ID */
85     uint8_t     spn_dev;       /* Device ID */
94 Low-level datagram protocol
95 ---------------------------
98 protocol from the PF_PHONET family. Each socket is bound to one of the
117 This protocol follows the SOCK_DGRAM connection-less semantics.
123 ---------------------
125 A Phonet datagram socket can be subscribed to any number of 8-bits
138 Phonet Pipe protocol
139 --------------------
141 The Phonet Pipe protocol is a simple sequenced packets protocol
142 with end-to-end congestion control. It uses the passive listening
144 ID. Each listening socket can handle up to 255 simultaneous
173 e.g. the Nokia Slim Modem in the ST-Ericsson U8500 platform::
194    block until write becomes possible again, unless non-blocking mode
198 The pipe protocol provides two socket options at the SOL_PNPIPE level:
212       is a read-only integer value. It contains the
217       is a read-only integer value. It contains the underlying
223 -------
228 Carlos Chinea and Rémi Denis-Courmont.