- The Linux LAPB Module Interface 1.3
+.. SPDX-License-Identifier: GPL-2.0
- Jonathan Naylor 29.12.96
+===============================
+The Linux LAPB Module Interface
+===============================
-Changed (Henner Eisen, 2000-10-29): int return value for data_indication()
+Version 1.3
+
+Jonathan Naylor 29.12.96
+
+Changed (Henner Eisen, 2000-10-29): int return value for data_indication()
The LAPB module will be a separately compiled module for use by any parts of
the Linux operating system that require a LAPB service. This document
This structure is used only once, in the call to lapb_register (see below).
It contains information about the device driver that requires the services
-of the LAPB module.
+of the LAPB module::
-struct lapb_register_struct {
- void (*connect_confirmation)(int token, int reason);
- void (*connect_indication)(int token, int reason);
- void (*disconnect_confirmation)(int token, int reason);
- void (*disconnect_indication)(int token, int reason);
- int (*data_indication)(int token, struct sk_buff *skb);
- void (*data_transmit)(int token, struct sk_buff *skb);
-};
+ struct lapb_register_struct {
+ void (*connect_confirmation)(int token, int reason);
+ void (*connect_indication)(int token, int reason);
+ void (*disconnect_confirmation)(int token, int reason);
+ void (*disconnect_indication)(int token, int reason);
+ int (*data_indication)(int token, struct sk_buff *skb);
+ void (*data_transmit)(int token, struct sk_buff *skb);
+ };
Each member of this structure corresponds to a function in the device driver
that is called when a particular event in the LAPB module occurs. These will
This structure is used with the lapb_getparms and lapb_setparms functions
(see below). They are used to allow the device driver to get and set the
-operational parameters of the LAPB implementation for a given connection.
-
-struct lapb_parms_struct {
- unsigned int t1;
- unsigned int t1timer;
- unsigned int t2;
- unsigned int t2timer;
- unsigned int n2;
- unsigned int n2count;
- unsigned int window;
- unsigned int state;
- unsigned int mode;
-};
+operational parameters of the LAPB implementation for a given connection::
+
+ struct lapb_parms_struct {
+ unsigned int t1;
+ unsigned int t1timer;
+ unsigned int t2;
+ unsigned int t2timer;
+ unsigned int n2;
+ unsigned int n2count;
+ unsigned int window;
+ unsigned int state;
+ unsigned int mode;
+ };
T1 and T2 are protocol timing parameters and are given in units of 100ms. N2
is the maximum number of tries on the link before it is declared a failure.
The mode variable is a bit field used for setting (at present) three values.
The bit fields have the following meanings:
+====== =================================================
Bit Meaning
+====== =================================================
0 LAPB operation (0=LAPB_STANDARD 1=LAPB_EXTENDED).
1 [SM]LP operation (0=LAPB_SLP 1=LAPB=MLP).
2 DTE/DCE operation (0=LAPB_DTE 1=LAPB_DCE)
3-31 Reserved, must be 0.
+====== =================================================
Extended LAPB operation indicates the use of extended sequence numbers and
consequently larger window sizes, the default is standard LAPB operation.
The LAPB module provides a number of function entry points.
+::
-int lapb_register(void *token, struct lapb_register_struct);
+ int lapb_register(void *token, struct lapb_register_struct);
This must be called before the LAPB module may be used. If the call is
successful then LAPB_OK is returned. The token must be a unique identifier
lapb_register must be made. The format of the lapb_register_struct is given
above. The return values are:
+============= =============================
LAPB_OK LAPB registered successfully.
LAPB_BADTOKEN Token is already registered.
LAPB_NOMEM Out of memory
+============= =============================
+::
-int lapb_unregister(void *token);
+ int lapb_unregister(void *token);
This releases all the resources associated with a LAPB link. Any current
LAPB link will be abandoned without further messages being passed. After
this call, the value of token is no longer valid for any calls to the LAPB
function. The valid return values are:
+============= ===============================
LAPB_OK LAPB unregistered successfully.
LAPB_BADTOKEN Invalid/unknown LAPB token.
+============= ===============================
+::
-int lapb_getparms(void *token, struct lapb_parms_struct *parms);
+ int lapb_getparms(void *token, struct lapb_parms_struct *parms);
This allows the device driver to get the values of the current LAPB
variables, the lapb_parms_struct is described above. The valid return values
are:
+============= =============================
LAPB_OK LAPB getparms was successful.
LAPB_BADTOKEN Invalid/unknown LAPB token.
+============= =============================
+::
-int lapb_setparms(void *token, struct lapb_parms_struct *parms);
+ int lapb_setparms(void *token, struct lapb_parms_struct *parms);
This allows the device driver to set the values of the current LAPB
variables, the lapb_parms_struct is described above. The values of t1timer,
connected will be ignored. An error implies that none of the values have
been changed. The valid return values are:
+============= =================================================
LAPB_OK LAPB getparms was successful.
LAPB_BADTOKEN Invalid/unknown LAPB token.
LAPB_INVALUE One of the values was out of its allowable range.
+============= =================================================
+::
-int lapb_connect_request(void *token);
+ int lapb_connect_request(void *token);
Initiate a connect using the current parameter settings. The valid return
values are:
+============== =================================
LAPB_OK LAPB is starting to connect.
LAPB_BADTOKEN Invalid/unknown LAPB token.
LAPB_CONNECTED LAPB module is already connected.
+============== =================================
+::
-int lapb_disconnect_request(void *token);
+ int lapb_disconnect_request(void *token);
Initiate a disconnect. The valid return values are:
+================= ===============================
LAPB_OK LAPB is starting to disconnect.
LAPB_BADTOKEN Invalid/unknown LAPB token.
LAPB_NOTCONNECTED LAPB module is not connected.
+================= ===============================
+::
-int lapb_data_request(void *token, struct sk_buff *skb);
+ int lapb_data_request(void *token, struct sk_buff *skb);
Queue data with the LAPB module for transmitting over the link. If the call
is successful then the skbuff is owned by the LAPB module and may not be
used by the device driver again. The valid return values are:
+================= =============================
LAPB_OK LAPB has accepted the data.
LAPB_BADTOKEN Invalid/unknown LAPB token.
LAPB_NOTCONNECTED LAPB module is not connected.
+================= =============================
+::
-int lapb_data_received(void *token, struct sk_buff *skb);
+ int lapb_data_received(void *token, struct sk_buff *skb);
Queue data with the LAPB module which has been received from the device. It
is expected that the data passed to the LAPB module has skb->data pointing
is owned by the LAPB module and may not be used by the device driver again.
The valid return values are:
+============= ===========================
LAPB_OK LAPB has accepted the data.
LAPB_BADTOKEN Invalid/unknown LAPB token.
-
+============= ===========================
Callbacks
---------
module with lapb_register (see above) in the structure lapb_register_struct
(see above).
+::
-void (*connect_confirmation)(void *token, int reason);
+ void (*connect_confirmation)(void *token, int reason);
This is called by the LAPB module when a connection is established after
being requested by a call to lapb_connect_request (see above). The reason is
always LAPB_OK.
+::
-void (*connect_indication)(void *token, int reason);
+ void (*connect_indication)(void *token, int reason);
This is called by the LAPB module when the link is established by the remote
system. The value of reason is always LAPB_OK.
+::
-void (*disconnect_confirmation)(void *token, int reason);
+ void (*disconnect_confirmation)(void *token, int reason);
This is called by the LAPB module when an event occurs after the device
driver has called lapb_disconnect_request (see above). The reason indicates
what has happened. In all cases the LAPB link can be regarded as being
terminated. The values for reason are:
+================= ====================================================
LAPB_OK The LAPB link was terminated normally.
LAPB_NOTCONNECTED The remote system was not connected.
LAPB_TIMEDOUT No response was received in N2 tries from the remote
system.
+================= ====================================================
+::
-void (*disconnect_indication)(void *token, int reason);
+ void (*disconnect_indication)(void *token, int reason);
This is called by the LAPB module when the link is terminated by the remote
system or another event has occurred to terminate the link. This may be
returned in response to a lapb_connect_request (see above) if the remote
system refused the request. The values for reason are:
+================= ====================================================
LAPB_OK The LAPB link was terminated normally by the remote
system.
LAPB_REFUSED The remote system refused the connect request.
LAPB_NOTCONNECTED The remote system was not connected.
LAPB_TIMEDOUT No response was received in N2 tries from the remote
system.
+================= ====================================================
+::
-int (*data_indication)(void *token, struct sk_buff *skb);
+ int (*data_indication)(void *token, struct sk_buff *skb);
This is called by the LAPB module when data has been received from the
remote system that should be passed onto the next layer in the protocol
file include/linux/netdevice.h) if and only if the frame was dropped
before it could be delivered to the upper layer.
+::
-void (*data_transmit)(void *token, struct sk_buff *skb);
+ void (*data_transmit)(void *token, struct sk_buff *skb);
This is called by the LAPB module when data is to be transmitted to the
remote system by the device driver. The skbuff becomes the property of the
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