2296e5a013
Move the entry about CAPI 2.0 to the beginning and add a URL. Incorporate changes suggested by Randy Dunlap, thanks for proofreading. Signed-off-by: Karsten Keil <keil@b1-systems.de> Signed-off-by: David S. Miller <davem@davemloft.net>
213 lines
8.2 KiB
Text
213 lines
8.2 KiB
Text
Kernel CAPI Interface to Hardware Drivers
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-----------------------------------------
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1. Overview
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From the CAPI 2.0 specification:
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COMMON-ISDN-API (CAPI) is an application programming interface standard used
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to access ISDN equipment connected to basic rate interfaces (BRI) and primary
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rate interfaces (PRI).
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Kernel CAPI operates as a dispatching layer between CAPI applications and CAPI
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hardware drivers. Hardware drivers register ISDN devices (controllers, in CAPI
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lingo) with Kernel CAPI to indicate their readiness to provide their service
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to CAPI applications. CAPI applications also register with Kernel CAPI,
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requesting association with a CAPI device. Kernel CAPI then dispatches the
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application registration to an available device, forwarding it to the
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corresponding hardware driver. Kernel CAPI then forwards CAPI messages in both
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directions between the application and the hardware driver.
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Format and semantics of CAPI messages are specified in the CAPI 2.0 standard.
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This standard is freely available from http://www.capi.org.
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2. Driver and Device Registration
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CAPI drivers optionally register themselves with Kernel CAPI by calling the
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Kernel CAPI function register_capi_driver() with a pointer to a struct
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capi_driver. This structure must be filled with the name and revision of the
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driver, and optionally a pointer to a callback function, add_card(). The
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registration can be revoked by calling the function unregister_capi_driver()
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with a pointer to the same struct capi_driver.
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CAPI drivers must register each of the ISDN devices they control with Kernel
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CAPI by calling the Kernel CAPI function attach_capi_ctr() with a pointer to a
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struct capi_ctr before they can be used. This structure must be filled with
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the names of the driver and controller, and a number of callback function
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pointers which are subsequently used by Kernel CAPI for communicating with the
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driver. The registration can be revoked by calling the function
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detach_capi_ctr() with a pointer to the same struct capi_ctr.
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Before the device can be actually used, the driver must fill in the device
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information fields 'manu', 'version', 'profile' and 'serial' in the capi_ctr
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structure of the device, and signal its readiness by calling capi_ctr_ready().
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From then on, Kernel CAPI may call the registered callback functions for the
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device.
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If the device becomes unusable for any reason (shutdown, disconnect ...), the
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driver has to call capi_ctr_reseted(). This will prevent further calls to the
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callback functions by Kernel CAPI.
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3. Application Registration and Communication
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Kernel CAPI forwards registration requests from applications (calls to CAPI
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operation CAPI_REGISTER) to an appropriate hardware driver by calling its
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register_appl() callback function. A unique Application ID (ApplID, u16) is
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allocated by Kernel CAPI and passed to register_appl() along with the
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parameter structure provided by the application. This is analogous to the
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open() operation on regular files or character devices.
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After a successful return from register_appl(), CAPI messages from the
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application may be passed to the driver for the device via calls to the
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send_message() callback function. The CAPI message to send is stored in the
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data portion of an skb. Conversely, the driver may call Kernel CAPI's
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capi_ctr_handle_message() function to pass a received CAPI message to Kernel
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CAPI for forwarding to an application, specifying its ApplID.
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Deregistration requests (CAPI operation CAPI_RELEASE) from applications are
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forwarded as calls to the release_appl() callback function, passing the same
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ApplID as with register_appl(). After return from release_appl(), no CAPI
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messages for that application may be passed to or from the device anymore.
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4. Data Structures
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4.1 struct capi_driver
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This structure describes a Kernel CAPI driver itself. It is used in the
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register_capi_driver() and unregister_capi_driver() functions, and contains
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the following non-private fields, all to be set by the driver before calling
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register_capi_driver():
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char name[32]
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the name of the driver, as a zero-terminated ASCII string
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char revision[32]
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the revision number of the driver, as a zero-terminated ASCII string
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int (*add_card)(struct capi_driver *driver, capicardparams *data)
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a callback function pointer (may be NULL)
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4.2 struct capi_ctr
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This structure describes an ISDN device (controller) handled by a Kernel CAPI
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driver. After registration via the attach_capi_ctr() function it is passed to
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all controller specific lower layer interface and callback functions to
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identify the controller to operate on.
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It contains the following non-private fields:
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- to be set by the driver before calling attach_capi_ctr():
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struct module *owner
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pointer to the driver module owning the device
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void *driverdata
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an opaque pointer to driver specific data, not touched by Kernel CAPI
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char name[32]
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the name of the controller, as a zero-terminated ASCII string
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char *driver_name
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the name of the driver, as a zero-terminated ASCII string
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int (*load_firmware)(struct capi_ctr *ctrlr, capiloaddata *ldata)
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(optional) pointer to a callback function for sending firmware and
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configuration data to the device
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void (*reset_ctr)(struct capi_ctr *ctrlr)
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pointer to a callback function for performing a reset on the device,
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releasing all registered applications
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void (*register_appl)(struct capi_ctr *ctrlr, u16 applid,
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capi_register_params *rparam)
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void (*release_appl)(struct capi_ctr *ctrlr, u16 applid)
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pointers to callback functions for registration and deregistration of
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applications with the device
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u16 (*send_message)(struct capi_ctr *ctrlr, struct sk_buff *skb)
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pointer to a callback function for sending a CAPI message to the
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device
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char *(*procinfo)(struct capi_ctr *ctrlr)
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pointer to a callback function returning the entry for the device in
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the CAPI controller info table, /proc/capi/controller
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read_proc_t *ctr_read_proc
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pointer to the read_proc callback function for the device's proc file
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system entry, /proc/capi/controllers/<n>; will be called with a
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pointer to the device's capi_ctr structure as the last (data) argument
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- to be filled in before calling capi_ctr_ready():
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u8 manu[CAPI_MANUFACTURER_LEN]
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value to return for CAPI_GET_MANUFACTURER
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capi_version version
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value to return for CAPI_GET_VERSION
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capi_profile profile
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value to return for CAPI_GET_PROFILE
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u8 serial[CAPI_SERIAL_LEN]
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value to return for CAPI_GET_SERIAL
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5. Lower Layer Interface Functions
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(declared in <linux/isdn/capilli.h>)
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void register_capi_driver(struct capi_driver *drvr)
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void unregister_capi_driver(struct capi_driver *drvr)
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register/unregister a driver with Kernel CAPI
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int attach_capi_ctr(struct capi_ctr *ctrlr)
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int detach_capi_ctr(struct capi_ctr *ctrlr)
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register/unregister a device (controller) with Kernel CAPI
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void capi_ctr_ready(struct capi_ctr *ctrlr)
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void capi_ctr_reseted(struct capi_ctr *ctrlr)
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signal controller ready/not ready
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void capi_ctr_suspend_output(struct capi_ctr *ctrlr)
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void capi_ctr_resume_output(struct capi_ctr *ctrlr)
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signal suspend/resume
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void capi_ctr_handle_message(struct capi_ctr * ctrlr, u16 applid,
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struct sk_buff *skb)
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pass a received CAPI message to Kernel CAPI
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for forwarding to the specified application
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6. Helper Functions and Macros
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Library functions (from <linux/isdn/capilli.h>):
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void capilib_new_ncci(struct list_head *head, u16 applid,
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u32 ncci, u32 winsize)
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void capilib_free_ncci(struct list_head *head, u16 applid, u32 ncci)
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void capilib_release_appl(struct list_head *head, u16 applid)
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void capilib_release(struct list_head *head)
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void capilib_data_b3_conf(struct list_head *head, u16 applid,
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u32 ncci, u16 msgid)
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u16 capilib_data_b3_req(struct list_head *head, u16 applid,
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u32 ncci, u16 msgid)
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Macros to extract/set element values from/in a CAPI message header
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(from <linux/isdn/capiutil.h>):
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Get Macro Set Macro Element (Type)
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CAPIMSG_LEN(m) CAPIMSG_SETLEN(m, len) Total Length (u16)
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CAPIMSG_APPID(m) CAPIMSG_SETAPPID(m, applid) ApplID (u16)
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CAPIMSG_COMMAND(m) CAPIMSG_SETCOMMAND(m,cmd) Command (u8)
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CAPIMSG_SUBCOMMAND(m) CAPIMSG_SETSUBCOMMAND(m, cmd) Subcommand (u8)
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CAPIMSG_CMD(m) - Command*256
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+ Subcommand (u16)
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CAPIMSG_MSGID(m) CAPIMSG_SETMSGID(m, msgid) Message Number (u16)
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CAPIMSG_CONTROL(m) CAPIMSG_SETCONTROL(m, contr) Controller/PLCI/NCCI
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(u32)
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CAPIMSG_DATALEN(m) CAPIMSG_SETDATALEN(m, len) Data Length (u16)
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