337 строки
12 KiB
ReStructuredText
337 строки
12 KiB
ReStructuredText
=========================================
|
|
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 https://www.capi.org.
|
|
|
|
|
|
2. Driver and Device Registration
|
|
=================================
|
|
|
|
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_down(). 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. 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
|
|
|
|
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
|
|
|
|
The function may return before the operation has completed.
|
|
|
|
Completion must be signalled by a call to capi_ctr_ready().
|
|
|
|
Return value: 0 on success, error code on error
|
|
Called in process context.
|
|
|
|
``void (*reset_ctr)(struct capi_ctr *ctrlr)``
|
|
(optional) pointer to a callback function for stopping the device,
|
|
releasing all registered applications
|
|
|
|
The function may return before the operation has completed.
|
|
|
|
Completion must be signalled by a call to capi_ctr_down().
|
|
|
|
Called in process context.
|
|
|
|
``void (*register_appl)(struct capi_ctr *ctrlr, u16 applid, capi_register_params *rparam)``
|
|
pointers to callback function for registration of
|
|
applications with the device
|
|
|
|
Calls to these functions are serialized by Kernel CAPI so that only
|
|
one call to any of them is active at any time.
|
|
|
|
``void (*release_appl)(struct capi_ctr *ctrlr, u16 applid)``
|
|
pointers to callback functions deregistration of
|
|
applications with the device
|
|
|
|
Calls to these functions are serialized by Kernel CAPI so that only
|
|
one call to any of them is active at any time.
|
|
|
|
``u16 (*send_message)(struct capi_ctr *ctrlr, struct sk_buff *skb)``
|
|
pointer to a callback function for sending a CAPI message to the
|
|
device
|
|
|
|
Return value: CAPI error code
|
|
|
|
If the method returns 0 (CAPI_NOERROR) the driver has taken ownership
|
|
of the skb and the caller may no longer access it. If it returns a
|
|
non-zero (error) value then ownership of the skb returns to the caller
|
|
who may reuse or free it.
|
|
|
|
The return value should only be used to signal problems with respect
|
|
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.
|
|
|
|
``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
|
|
|
|
Note:
|
|
Callback functions except send_message() are never called in interrupt
|
|
context.
|
|
|
|
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
|
|
|
|
|
|
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 <linux/isdn/capiutil.h>)
|
|
|
|
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,
|
|
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 <linux/isdn/capiutil.h> for the exact spelling. Member data
|
|
types are:
|
|
|
|
=========== =================================================================
|
|
u8 for CAPI parameters of type 'byte'
|
|
|
|
u16 for CAPI parameters of type 'word'
|
|
|
|
u32 for CAPI parameters of type 'dword'
|
|
|
|
_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 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/absent.
|
|
CAPI_COMPOSE: The parameter is present.
|
|
Subparameter values are stored individually in the corresponding
|
|
_cmsg structure members.
|
|
=========== =================================================================
|
|
|
|
|
|
5. Lower Layer Interface Functions
|
|
==================================
|
|
|
|
::
|
|
|
|
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_down(struct capi_ctr *ctrlr)
|
|
|
|
signal controller ready/not ready
|
|
|
|
::
|
|
|
|
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
|
|
==============================
|
|
|
|
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)
|
|
====================== ============================= ====================
|
|
|
|
|
|
Library functions for working with _cmsg structures
|
|
(from <linux/isdn/capiutil.h>):
|
|
|
|
``char *capi_cmd2str(u8 Command, u8 Subcommand)``
|
|
Returns the CAPI 2.0 message name corresponding to the given command
|
|
and subcommand values, as a static ASCII string. The return value may
|
|
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=<n>" 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 the 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.
|