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diff --git a/Documentation/networking/lapb-module.txt b/Documentation/networking/lapb-module.txt new file mode 100644 index 000000000000..d4fc8f221559 --- /dev/null +++ b/Documentation/networking/lapb-module.txt @@ -0,0 +1,263 @@ + The Linux LAPB Module Interface 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 +defines the interfaces to, and the services provided by this module. The +term module in this context does not imply that the LAPB module is a +separately loadable module, although it may be. The term module is used in +its more standard meaning. + +The interface to the LAPB module consists of functions to the module, +callbacks from the module to indicate important state changes, and +structures for getting and setting information about the module. + +Structures +---------- + +Probably the most important structure is the skbuff structure for holding +received and transmitted data, however it is beyond the scope of this +document. + +The two LAPB specific structures are the LAPB initialisation structure and +the LAPB parameter structure. These will be defined in a standard header +file, <linux/lapb.h>. The header file <net/lapb.h> is internal to the LAPB +module and is not for use. + +LAPB Initialisation Structure +----------------------------- + +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. + +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 +be described in detail below. If a callback is not required (!!) then a NULL +may be substituted. + + +LAPB Parameter Structure +------------------------ + +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; +}; + +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 window size is the maximum number of outstanding data packets allowed to +be unacknowledged by the remote end, the value of the window is between 1 +and 7 for a standard LAPB link, and between 1 and 127 for an extended LAPB +link. + +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. +MLP operation is the same as SLP operation except that the addresses used by +LAPB are different to indicate the mode of operation, the default is Single +Link Procedure. The difference between DCE and DTE operation is (i) the +addresses used for commands and responses, and (ii) when the DCE is not +connected, it sends DM without polls set, every T1. The upper case constant +names will be defined in the public LAPB header file. + + +Functions +--------- + +The LAPB module provides a number of function entry points. + + +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 +generated by the device driver to allow for the unique identification of the +instance of the LAPB link. It is returned by the LAPB module in all of the +callbacks, and is used by the device driver in all calls to the LAPB module. +For multiple LAPB links in a single device driver, multiple calls to +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); + +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); + +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); + +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, +t2timer and n2count are ignored, likewise changing the mode bits when +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); + +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); + +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); + +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); + +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 +to the beginning of the LAPB data. 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. + + +Callbacks +--------- + +These callbacks are functions provided by the device driver for the LAPB +module to call when an event occurs. They are registered with the LAPB +module with lapb_register (see above) in the structure lapb_register_struct +(see above). + + +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); + +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); + +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); + +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); + +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 +stack. The skbuff becomes the property of the device driver and the LAPB +module will not perform any more actions on it. The skb->data pointer will +be pointing to the first byte of data after the LAPB header. + +This method should return NET_RX_DROP (as defined in the header +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); + +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 +device driver and the LAPB module will not perform any more actions on it. +The skb->data pointer will be pointing to the first byte of the LAPB header. |