From f1af9f58546e2d98ef078fa30b2ef80a9042131e Mon Sep 17 00:00:00 2001 From: Tilman Schmidt Date: Tue, 6 Oct 2009 12:18:00 +0000 Subject: [PATCH] Documentation: expand isdn/INTERFACE.CAPI document - Note that send_message() may be called in interrupt context. - Describe the storage of CAPI messages and payload data in SKBs. - Add more details to the description of the _cmsg structure. - Describe kernelcapi debugging output. Impact: documentation Signed-off-by: Tilman Schmidt Signed-off-by: David S. Miller --- Documentation/isdn/INTERFACE.CAPI | 83 +++++++++++++++++++++++++------ 1 file changed, 67 insertions(+), 16 deletions(-) diff --git a/Documentation/isdn/INTERFACE.CAPI b/Documentation/isdn/INTERFACE.CAPI index 686e107923ec..5fe8de5cc727 100644 --- a/Documentation/isdn/INTERFACE.CAPI +++ b/Documentation/isdn/INTERFACE.CAPI @@ -60,10 +60,9 @@ open() operation on regular files or character devices. After a successful return from register_appl(), CAPI messages from the application may be passed to the driver for the device via calls to the -send_message() callback function. The CAPI message to send is stored in the -data portion of an skb. Conversely, the driver may call Kernel CAPI's -capi_ctr_handle_message() function to pass a received CAPI message to Kernel -CAPI for forwarding to an application, specifying its ApplID. +send_message() callback function. Conversely, the driver may call Kernel +CAPI's capi_ctr_handle_message() function to pass a received CAPI message to +Kernel CAPI for forwarding to an application, specifying its ApplID. Deregistration requests (CAPI operation CAPI_RELEASE) from applications are forwarded as calls to the release_appl() callback function, passing the same @@ -142,6 +141,7 @@ u16 (*send_message)(struct capi_ctr *ctrlr, struct sk_buff *skb) to accepting or queueing the message. Errors occurring during the actual processing of the message should be signaled with an appropriate reply message. + May be called in process or interrupt context. Calls to this function are not serialized by Kernel CAPI, ie. it must be prepared to be re-entered. @@ -154,7 +154,8 @@ read_proc_t *ctr_read_proc system entry, /proc/capi/controllers/; will be called with a pointer to the device's capi_ctr structure as the last (data) argument -Note: Callback functions are never called in interrupt context. +Note: Callback functions except send_message() are never called in interrupt +context. - to be filled in before calling capi_ctr_ready(): @@ -171,14 +172,40 @@ u8 serial[CAPI_SERIAL_LEN] value to return for CAPI_GET_SERIAL -4.3 The _cmsg Structure +4.3 SKBs + +CAPI messages are passed between Kernel CAPI and the driver via send_message() +and capi_ctr_handle_message(), stored in the data portion of a socket buffer +(skb). Each skb contains a single CAPI message coded according to the CAPI 2.0 +standard. + +For the data transfer messages, DATA_B3_REQ and DATA_B3_IND, the actual +payload data immediately follows the CAPI message itself within the same skb. +The Data and Data64 parameters are not used for processing. The Data64 +parameter may be omitted by setting the length field of the CAPI message to 22 +instead of 30. + + +4.4 The _cmsg Structure (declared in ) The _cmsg structure stores the contents of a CAPI 2.0 message in an easily -accessible form. It contains members for all possible CAPI 2.0 parameters, of -which only those appearing in the message type currently being processed are -actually used. Unused members should be set to zero. +accessible form. It contains members for all possible CAPI 2.0 parameters, +including subparameters of the Additional Info and B Protocol structured +parameters, with the following exceptions: + +* second Calling party number (CONNECT_IND) + +* Data64 (DATA_B3_REQ and DATA_B3_IND) + +* Sending complete (subparameter of Additional Info, CONNECT_REQ and INFO_REQ) + +* Global Configuration (subparameter of B Protocol, CONNECT_REQ, CONNECT_RESP + and SELECT_B_PROTOCOL_REQ) + +Only those parameters appearing in the message type currently being processed +are actually used. Unused members should be set to zero. Members are named after the CAPI 2.0 standard names of the parameters they represent. See for the exact spelling. Member data @@ -190,18 +217,19 @@ u16 for CAPI parameters of type 'word' u32 for CAPI parameters of type 'dword' -_cstruct for CAPI parameters of type 'struct' not containing any - variably-sized (struct) subparameters (eg. 'Called Party Number') +_cstruct for CAPI parameters of type 'struct' The member is a pointer to a buffer containing the parameter in CAPI encoding (length + content). It may also be NULL, which will be taken to represent an empty (zero length) parameter. + Subparameters are stored in encoded form within the content part. -_cmstruct for CAPI parameters of type 'struct' containing 'struct' - subparameters ('Additional Info' and 'B Protocol') +_cmstruct alternative representation for CAPI parameters of type 'struct' + (used only for the 'Additional Info' and 'B Protocol' parameters) The representation is a single byte containing one of the values: - CAPI_DEFAULT: the parameter is empty - CAPI_COMPOSE: the values of the subparameters are stored - individually in the corresponding _cmsg structure members + CAPI_DEFAULT: The parameter is empty/absent. + CAPI_COMPOSE: The parameter is present. + Subparameter values are stored individually in the corresponding + _cmsg structure members. Functions capi_cmsg2message() and capi_message2cmsg() are provided to convert messages between their transport encoding described in the CAPI 2.0 standard @@ -297,3 +325,26 @@ char *capi_cmd2str(u8 Command, u8 Subcommand) be NULL if the command/subcommand is not one of those defined in the CAPI 2.0 standard. + +7. Debugging + +The module kernelcapi has a module parameter showcapimsgs controlling some +debugging output produced by the module. It can only be set when the module is +loaded, via a parameter "showcapimsgs=" to the modprobe command, either on +the command line or in the configuration file. + +If the lowest bit of showcapimsgs is set, kernelcapi logs controller and +application up and down events. + +In addition, every registered CAPI controller has an associated traceflag +parameter controlling how CAPI messages sent from and to tha controller are +logged. The traceflag parameter is initialized with the value of the +showcapimsgs parameter when the controller is registered, but can later be +changed via the MANUFACTURER_REQ command KCAPI_CMD_TRACE. + +If the value of traceflag is non-zero, CAPI messages are logged. +DATA_B3 messages are only logged if the value of traceflag is > 2. + +If the lowest bit of traceflag is set, only the command/subcommand and message +length are logged. Otherwise, kernelcapi logs a readable representation of +the entire message. -- 2.20.1