projects / linux-block.git / blame
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|---|---|---|
| 883780af MCC |
1 | .. SPDX-License-Identifier: GPL-2.0 |
| 2 | ||
| 3 | ============================- | |
| 4 | X.25 Device Driver Interface | |
| 5 | ============================- | |
| 6 | ||
| 7 | Version 1.1 | |
| 1da177e4 LT |
8 | |
| 9 | Jonathan Naylor 26.12.96 | |
| 10 | ||
| 11 | This is a description of the messages to be passed between the X.25 Packet | |
| 12 | Layer and the X.25 device driver. They are designed to allow for the easy | |
| 13 | setting of the LAPB mode from within the Packet Layer. | |
| 14 | ||
| 15 | The X.25 device driver will be coded normally as per the Linux device driver | |
| 16 | standards. Most X.25 device drivers will be moderately similar to the | |
| 17 | already existing Ethernet device drivers. However unlike those drivers, the | |
| 18 | X.25 device driver has a state associated with it, and this information | |
| 19 | needs to be passed to and from the Packet Layer for proper operation. | |
| 20 | ||
| 21 | All messages are held in sk_buff's just like real data to be transmitted | |
| 22 | over the LAPB link. The first byte of the skbuff indicates the meaning of | |
| 23 | the rest of the skbuff, if any more information does exist. | |
| 24 | ||
| 25 | ||
| 26 | Packet Layer to Device Driver | |
| 27 | ----------------------------- | |
| 28 | ||
| e904f0a4 | 29 | First Byte = 0x00 (X25_IFACE_DATA) |
| 1da177e4 LT |
30 | |
| 31 | This indicates that the rest of the skbuff contains data to be transmitted | |
| 32 | over the LAPB link. The LAPB link should already exist before any data is | |
| 33 | passed down. | |
| 34 | ||
| e904f0a4 | 35 | First Byte = 0x01 (X25_IFACE_CONNECT) |
| 1da177e4 LT |
36 | |
| 37 | Establish the LAPB link. If the link is already established then the connect | |
| 38 | confirmation message should be returned as soon as possible. | |
| 39 | ||
| e904f0a4 | 40 | First Byte = 0x02 (X25_IFACE_DISCONNECT) |
| 1da177e4 LT |
41 | |
| 42 | Terminate the LAPB link. If it is already disconnected then the disconnect | |
| 43 | confirmation message should be returned as soon as possible. | |
| 44 | ||
| e904f0a4 | 45 | First Byte = 0x03 (X25_IFACE_PARAMS) |
| 1da177e4 LT |
46 | |
| 47 | LAPB parameters. To be defined. | |
| 48 | ||
| 49 | ||
| 50 | Device Driver to Packet Layer | |
| 51 | ----------------------------- | |
| 52 | ||
| e904f0a4 | 53 | First Byte = 0x00 (X25_IFACE_DATA) |
| 1da177e4 LT |
54 | |
| 55 | This indicates that the rest of the skbuff contains data that has been | |
| 56 | received over the LAPB link. | |
| 57 | ||
| e904f0a4 | 58 | First Byte = 0x01 (X25_IFACE_CONNECT) |
| 1da177e4 LT |
59 | |
| 60 | LAPB link has been established. The same message is used for both a LAPB | |
| 61 | link connect_confirmation and a connect_indication. | |
| 62 | ||
| e904f0a4 | 63 | First Byte = 0x02 (X25_IFACE_DISCONNECT) |
| 1da177e4 LT |
64 | |
| 65 | LAPB link has been terminated. This same message is used for both a LAPB | |
| 66 | link disconnect_confirmation and a disconnect_indication. | |
| 67 | ||
| e904f0a4 | 68 | First Byte = 0x03 (X25_IFACE_PARAMS) |
| 1da177e4 LT |
69 | |
| 70 | LAPB parameters. To be defined. | |
| 71 | ||
| 72 | ||
| 514e1150 XH |
73 | Requirements for the device driver |
| 74 | ---------------------------------- | |
| 1da177e4 | 75 | |
| 514e1150 XH |
76 | Packets should not be reordered or dropped when delivering between the |
| 77 | Packet Layer and the device driver. | |
| 78 | ||
| 79 | To avoid packets from being reordered or dropped when delivering from | |
| 80 | the device driver to the Packet Layer, the device driver should not | |
| 81 | call "netif_rx" to deliver the received packets. Instead, it should | |
| 82 | call "netif_receive_skb_core" from softirq context to deliver them. |