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Diffstat (limited to 'Documentation/isdn/INTERFACE.CAPI')
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diff --git a/Documentation/isdn/INTERFACE.CAPI b/Documentation/isdn/INTERFACE.CAPI new file mode 100644 index 000000000000..786d619b36e5 --- /dev/null +++ b/Documentation/isdn/INTERFACE.CAPI @@ -0,0 +1,213 @@ +Kernel CAPI Interface to Hardware Drivers +----------------------------------------- + +1. Overview + +From the CAPI 2.0 specification: +COMMON-ISDN-API (CAPI) is an application programming interface standard used +to access ISDN equipment connected to basic rate interfaces (BRI) and primary +rate interfaces (PRI). + +Kernel CAPI operates as a dispatching layer between CAPI applications and CAPI +hardware drivers. Hardware drivers register ISDN devices (controllers, in CAPI +lingo) with Kernel CAPI to indicate their readiness to provide their service +to CAPI applications. CAPI applications also register with Kernel CAPI, +requesting association with a CAPI device. Kernel CAPI then dispatches the +application registration to an available device, forwarding it to the +corresponding hardware driver. Kernel CAPI then forwards CAPI messages in both +directions between the application and the hardware driver. + +Format and semantics of CAPI messages are specified in the CAPI 2.0 standard. +This standard is freely available from http://www.capi.org. + + +2. Driver and Device Registration + +CAPI drivers optionally register themselves with Kernel CAPI by calling the +Kernel CAPI function register_capi_driver() with a pointer to a struct +capi_driver. This structure must be filled with the name and revision of the +driver, and optionally a pointer to a callback function, add_card(). The +registration can be revoked by calling the function unregister_capi_driver() +with a pointer to the same struct capi_driver. + +CAPI drivers must register each of the ISDN devices they control with Kernel +CAPI by calling the Kernel CAPI function attach_capi_ctr() with a pointer to a +struct capi_ctr before they can be used. This structure must be filled with +the names of the driver and controller, and a number of callback function +pointers which are subsequently used by Kernel CAPI for communicating with the +driver. The registration can be revoked by calling the function +detach_capi_ctr() with a pointer to the same struct capi_ctr. + +Before the device can be actually used, the driver must fill in the device +information fields 'manu', 'version', 'profile' and 'serial' in the capi_ctr +structure of the device, and signal its readiness by calling capi_ctr_ready(). +From then on, Kernel CAPI may call the registered callback functions for the +device. + +If the device becomes unusable for any reason (shutdown, disconnect ...), the +driver has to call capi_ctr_reseted(). This will prevent further calls to the +callback functions by Kernel CAPI. + + +3. Application Registration and Communication + +Kernel CAPI forwards registration requests from applications (calls to CAPI +operation CAPI_REGISTER) to an appropriate hardware driver by calling its +register_appl() callback function. A unique Application ID (ApplID, u16) is +allocated by Kernel CAPI and passed to register_appl() along with the +parameter structure provided by the application. This is analogous to the +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. + +Deregistration requests (CAPI operation CAPI_RELEASE) from applications are +forwarded as calls to the release_appl() callback function, passing the same +ApplID as with register_appl(). After return from release_appl(), no CAPI +messages for that application may be passed to or from the device anymore. + + +4. Data Structures + +4.1 struct capi_driver + +This structure describes a Kernel CAPI driver itself. It is used in the +register_capi_driver() and unregister_capi_driver() functions, and contains +the following non-private fields, all to be set by the driver before calling +register_capi_driver(): + +char name[32] + the name of the driver, as a zero-terminated ASCII string +char revision[32] + the revision number of the driver, as a zero-terminated ASCII string +int (*add_card)(struct capi_driver *driver, capicardparams *data) + a callback function pointer (may be NULL) + + +4.2 struct capi_ctr + +This structure describes an ISDN device (controller) handled by a Kernel CAPI +driver. After registration via the attach_capi_ctr() function it is passed to +all controller specific lower layer interface and callback functions to +identify the controller to operate on. + +It contains the following non-private fields: + +- to be set by the driver before calling attach_capi_ctr(): + +struct module *owner + pointer to the driver module owning the device + +void *driverdata + an opaque pointer to driver specific data, not touched by Kernel CAPI + +char name[32] + the name of the controller, as a zero-terminated ASCII string + +char *driver_name + the name of the driver, as a zero-terminated ASCII string + +int (*load_firmware)(struct capi_ctr *ctrlr, capiloaddata *ldata) + (optional) pointer to a callback function for sending firmware and + configuration data to the device + +void (*reset_ctr)(struct capi_ctr *ctrlr) + pointer to a callback function for performing a reset on the device, + releasing all registered applications + +void (*register_appl)(struct capi_ctr *ctrlr, u16 applid, + capi_register_params *rparam) +void (*release_appl)(struct capi_ctr *ctrlr, u16 applid) + pointers to callback functions for registration and deregistration of + applications with the device + +u16 (*send_message)(struct capi_ctr *ctrlr, struct sk_buff *skb) + pointer to a callback function for sending a CAPI message to the + device + +char *(*procinfo)(struct capi_ctr *ctrlr) + pointer to a callback function returning the entry for the device in + the CAPI controller info table, /proc/capi/controller + +read_proc_t *ctr_read_proc + pointer to the read_proc callback function for the device's proc file + system entry, /proc/capi/controllers/<n>; will be called with a + pointer to the device's capi_ctr structure as the last (data) argument + +- to be filled in before calling capi_ctr_ready(): + +u8 manu[CAPI_MANUFACTURER_LEN] + value to return for CAPI_GET_MANUFACTURER + +capi_version version + value to return for CAPI_GET_VERSION + +capi_profile profile + value to return for CAPI_GET_PROFILE + +u8 serial[CAPI_SERIAL_LEN] + value to return for CAPI_GET_SERIAL + + +5. Lower Layer Interface Functions + +(declared in <linux/isdn/capilli.h>) + +void register_capi_driver(struct capi_driver *drvr) +void unregister_capi_driver(struct capi_driver *drvr) + register/unregister a driver with Kernel CAPI + +int attach_capi_ctr(struct capi_ctr *ctrlr) +int detach_capi_ctr(struct capi_ctr *ctrlr) + register/unregister a device (controller) with Kernel CAPI + +void capi_ctr_ready(struct capi_ctr *ctrlr) +void capi_ctr_reseted(struct capi_ctr *ctrlr) + signal controller ready/not ready + +void capi_ctr_suspend_output(struct capi_ctr *ctrlr) +void capi_ctr_resume_output(struct capi_ctr *ctrlr) + signal suspend/resume + +void capi_ctr_handle_message(struct capi_ctr * ctrlr, u16 applid, + struct sk_buff *skb) + pass a received CAPI message to Kernel CAPI + for forwarding to the specified application + + +6. Helper Functions and Macros + +Library functions (from <linux/isdn/capilli.h>): + +void capilib_new_ncci(struct list_head *head, u16 applid, + u32 ncci, u32 winsize) +void capilib_free_ncci(struct list_head *head, u16 applid, u32 ncci) +void capilib_release_appl(struct list_head *head, u16 applid) +void capilib_release(struct list_head *head) +void capilib_data_b3_conf(struct list_head *head, u16 applid, + u32 ncci, u16 msgid) +u16 capilib_data_b3_req(struct list_head *head, u16 applid, + u32 ncci, u16 msgid) + + +Macros to extract/set element values from/in a CAPI message header +(from <linux/isdn/capiutil.h>): + +Get Macro Set Macro Element (Type) + +CAPIMSG_LEN(m) CAPIMSG_SETLEN(m, len) Total Length (u16) +CAPIMSG_APPID(m) CAPIMSG_SETAPPID(m, applid) ApplID (u16) +CAPIMSG_COMMAND(m) CAPIMSG_SETCOMMAND(m,cmd) Command (u8) +CAPIMSG_SUBCOMMAND(m) CAPIMSG_SETSUBCOMMAND(m, cmd) Subcommand (u8) +CAPIMSG_CMD(m) - Command*256 + + Subcommand (u16) +CAPIMSG_MSGID(m) CAPIMSG_SETMSGID(m, msgid) Message Number (u16) + +CAPIMSG_CONTROL(m) CAPIMSG_SETCONTROL(m, contr) Controller/PLCI/NCCI + (u32) +CAPIMSG_DATALEN(m) CAPIMSG_SETDATALEN(m, len) Data Length (u16) + |