1.. SPDX-License-Identifier: GPL-2.0
 2
 
 3X.25 Device Driver Interface
 4============================
 5
 6Version 1.1
 7
 8			   Jonathan Naylor 26.12.96
 9
10This is a description of the messages to be passed between the X.25 Packet
11Layer and the X.25 device driver. They are designed to allow for the easy
12setting of the LAPB mode from within the Packet Layer.
13
14The X.25 device driver will be coded normally as per the Linux device driver
15standards. Most X.25 device drivers will be moderately similar to the
16already existing Ethernet device drivers. However unlike those drivers, the
17X.25 device driver has a state associated with it, and this information
18needs to be passed to and from the Packet Layer for proper operation.
19
20All messages are held in sk_buff's just like real data to be transmitted
21over the LAPB link. The first byte of the skbuff indicates the meaning of
22the rest of the skbuff, if any more information does exist.
23
24
25Packet Layer to Device Driver
26-----------------------------
27
28First Byte = 0x00 (X25_IFACE_DATA)
29
30This indicates that the rest of the skbuff contains data to be transmitted
31over the LAPB link. The LAPB link should already exist before any data is
32passed down.
33
34First Byte = 0x01 (X25_IFACE_CONNECT)
35
36Establish the LAPB link. If the link is already established then the connect
37confirmation message should be returned as soon as possible.
38
39First Byte = 0x02 (X25_IFACE_DISCONNECT)
40
41Terminate the LAPB link. If it is already disconnected then the disconnect
42confirmation message should be returned as soon as possible.
43
44First Byte = 0x03 (X25_IFACE_PARAMS)
45
46LAPB parameters. To be defined.
47
48
49Device Driver to Packet Layer
50-----------------------------
51
52First Byte = 0x00 (X25_IFACE_DATA)
53
54This indicates that the rest of the skbuff contains data that has been
55received over the LAPB link.
56
57First Byte = 0x01 (X25_IFACE_CONNECT)
58
59LAPB link has been established. The same message is used for both a LAPB
60link connect_confirmation and a connect_indication.
61
62First Byte = 0x02 (X25_IFACE_DISCONNECT)
63
64LAPB link has been terminated. This same message is used for both a LAPB
65link disconnect_confirmation and a disconnect_indication.
66
67First Byte = 0x03 (X25_IFACE_PARAMS)
68
69LAPB parameters. To be defined.
70
71
72Requirements for the device driver
73----------------------------------
74
75Packets should not be reordered or dropped when delivering between the
76Packet Layer and the device driver.
77
78To avoid packets from being reordered or dropped when delivering from
79the device driver to the Packet Layer, the device driver should not
80call "netif_rx" to deliver the received packets. Instead, it should
81call "netif_receive_skb_core" from softirq context to deliver them.

 1.. SPDX-License-Identifier: GPL-2.0
 2
 3============================-
 4X.25 Device Driver Interface
 5============================-
 6
 7Version 1.1
 8
 9			   Jonathan Naylor 26.12.96
10
11This is a description of the messages to be passed between the X.25 Packet
12Layer and the X.25 device driver. They are designed to allow for the easy
13setting of the LAPB mode from within the Packet Layer.
14
15The X.25 device driver will be coded normally as per the Linux device driver
16standards. Most X.25 device drivers will be moderately similar to the
17already existing Ethernet device drivers. However unlike those drivers, the
18X.25 device driver has a state associated with it, and this information
19needs to be passed to and from the Packet Layer for proper operation.
20
21All messages are held in sk_buff's just like real data to be transmitted
22over the LAPB link. The first byte of the skbuff indicates the meaning of
23the rest of the skbuff, if any more information does exist.
24
25
26Packet Layer to Device Driver
27-----------------------------
28
29First Byte = 0x00 (X25_IFACE_DATA)
30
31This indicates that the rest of the skbuff contains data to be transmitted
32over the LAPB link. The LAPB link should already exist before any data is
33passed down.
34
35First Byte = 0x01 (X25_IFACE_CONNECT)
36
37Establish the LAPB link. If the link is already established then the connect
38confirmation message should be returned as soon as possible.
39
40First Byte = 0x02 (X25_IFACE_DISCONNECT)
41
42Terminate the LAPB link. If it is already disconnected then the disconnect
43confirmation message should be returned as soon as possible.
44
45First Byte = 0x03 (X25_IFACE_PARAMS)
46
47LAPB parameters. To be defined.
48
49
50Device Driver to Packet Layer
51-----------------------------
52
53First Byte = 0x00 (X25_IFACE_DATA)
54
55This indicates that the rest of the skbuff contains data that has been
56received over the LAPB link.
57
58First Byte = 0x01 (X25_IFACE_CONNECT)
59
60LAPB link has been established. The same message is used for both a LAPB
61link connect_confirmation and a connect_indication.
62
63First Byte = 0x02 (X25_IFACE_DISCONNECT)
64
65LAPB link has been terminated. This same message is used for both a LAPB
66link disconnect_confirmation and a disconnect_indication.
67
68First Byte = 0x03 (X25_IFACE_PARAMS)
69
70LAPB parameters. To be defined.
71
72
73Requirements for the device driver
74----------------------------------
75
76Packets should not be reordered or dropped when delivering between the
77Packet Layer and the device driver.
78
79To avoid packets from being reordered or dropped when delivering from
80the device driver to the Packet Layer, the device driver should not
81call "netif_rx" to deliver the received packets. Instead, it should
82call "netif_receive_skb_core" from softirq context to deliver them.