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Tilman Schmidt554f2002009-04-23 02:24:21 +00001Kernel CAPI Interface to Hardware Drivers
2-----------------------------------------
3
41. Overview
5
Karsten Keil2296e5a2009-04-23 02:24:21 +00006From the CAPI 2.0 specification:
7COMMON-ISDN-API (CAPI) is an application programming interface standard used
8to access ISDN equipment connected to basic rate interfaces (BRI) and primary
9rate interfaces (PRI).
10
Tilman Schmidt554f2002009-04-23 02:24:21 +000011Kernel CAPI operates as a dispatching layer between CAPI applications and CAPI
12hardware drivers. Hardware drivers register ISDN devices (controllers, in CAPI
13lingo) with Kernel CAPI to indicate their readiness to provide their service
14to CAPI applications. CAPI applications also register with Kernel CAPI,
15requesting association with a CAPI device. Kernel CAPI then dispatches the
16application registration to an available device, forwarding it to the
17corresponding hardware driver. Kernel CAPI then forwards CAPI messages in both
18directions between the application and the hardware driver.
19
Karsten Keil2296e5a2009-04-23 02:24:21 +000020Format and semantics of CAPI messages are specified in the CAPI 2.0 standard.
21This standard is freely available from http://www.capi.org.
22
Tilman Schmidt554f2002009-04-23 02:24:21 +000023
242. Driver and Device Registration
25
26CAPI drivers optionally register themselves with Kernel CAPI by calling the
27Kernel CAPI function register_capi_driver() with a pointer to a struct
28capi_driver. This structure must be filled with the name and revision of the
29driver, and optionally a pointer to a callback function, add_card(). The
30registration can be revoked by calling the function unregister_capi_driver()
31with a pointer to the same struct capi_driver.
32
33CAPI drivers must register each of the ISDN devices they control with Kernel
34CAPI by calling the Kernel CAPI function attach_capi_ctr() with a pointer to a
35struct capi_ctr before they can be used. This structure must be filled with
36the names of the driver and controller, and a number of callback function
37pointers which are subsequently used by Kernel CAPI for communicating with the
38driver. The registration can be revoked by calling the function
39detach_capi_ctr() with a pointer to the same struct capi_ctr.
40
41Before the device can be actually used, the driver must fill in the device
42information fields 'manu', 'version', 'profile' and 'serial' in the capi_ctr
43structure of the device, and signal its readiness by calling capi_ctr_ready().
44From then on, Kernel CAPI may call the registered callback functions for the
45device.
46
47If the device becomes unusable for any reason (shutdown, disconnect ...), the
48driver has to call capi_ctr_reseted(). This will prevent further calls to the
49callback functions by Kernel CAPI.
50
51
523. Application Registration and Communication
53
54Kernel CAPI forwards registration requests from applications (calls to CAPI
55operation CAPI_REGISTER) to an appropriate hardware driver by calling its
56register_appl() callback function. A unique Application ID (ApplID, u16) is
57allocated by Kernel CAPI and passed to register_appl() along with the
58parameter structure provided by the application. This is analogous to the
59open() operation on regular files or character devices.
60
61After a successful return from register_appl(), CAPI messages from the
62application may be passed to the driver for the device via calls to the
63send_message() callback function. The CAPI message to send is stored in the
Karsten Keil2296e5a2009-04-23 02:24:21 +000064data portion of an skb. Conversely, the driver may call Kernel CAPI's
Tilman Schmidt554f2002009-04-23 02:24:21 +000065capi_ctr_handle_message() function to pass a received CAPI message to Kernel
66CAPI for forwarding to an application, specifying its ApplID.
67
Tilman Schmidt554f2002009-04-23 02:24:21 +000068Deregistration requests (CAPI operation CAPI_RELEASE) from applications are
69forwarded as calls to the release_appl() callback function, passing the same
70ApplID as with register_appl(). After return from release_appl(), no CAPI
71messages for that application may be passed to or from the device anymore.
72
73
744. Data Structures
75
764.1 struct capi_driver
77
78This structure describes a Kernel CAPI driver itself. It is used in the
79register_capi_driver() and unregister_capi_driver() functions, and contains
80the following non-private fields, all to be set by the driver before calling
81register_capi_driver():
82
83char name[32]
Karsten Keil2296e5a2009-04-23 02:24:21 +000084 the name of the driver, as a zero-terminated ASCII string
Tilman Schmidt554f2002009-04-23 02:24:21 +000085char revision[32]
Karsten Keil2296e5a2009-04-23 02:24:21 +000086 the revision number of the driver, as a zero-terminated ASCII string
Tilman Schmidt554f2002009-04-23 02:24:21 +000087int (*add_card)(struct capi_driver *driver, capicardparams *data)
88 a callback function pointer (may be NULL)
89
90
914.2 struct capi_ctr
92
93This structure describes an ISDN device (controller) handled by a Kernel CAPI
94driver. After registration via the attach_capi_ctr() function it is passed to
95all controller specific lower layer interface and callback functions to
96identify the controller to operate on.
97
98It contains the following non-private fields:
99
100- to be set by the driver before calling attach_capi_ctr():
101
102struct module *owner
103 pointer to the driver module owning the device
104
105void *driverdata
106 an opaque pointer to driver specific data, not touched by Kernel CAPI
107
108char name[32]
Karsten Keil2296e5a2009-04-23 02:24:21 +0000109 the name of the controller, as a zero-terminated ASCII string
Tilman Schmidt554f2002009-04-23 02:24:21 +0000110
111char *driver_name
Karsten Keil2296e5a2009-04-23 02:24:21 +0000112 the name of the driver, as a zero-terminated ASCII string
Tilman Schmidt554f2002009-04-23 02:24:21 +0000113
114int (*load_firmware)(struct capi_ctr *ctrlr, capiloaddata *ldata)
115 (optional) pointer to a callback function for sending firmware and
116 configuration data to the device
117
118void (*reset_ctr)(struct capi_ctr *ctrlr)
119 pointer to a callback function for performing a reset on the device,
120 releasing all registered applications
121
122void (*register_appl)(struct capi_ctr *ctrlr, u16 applid,
123 capi_register_params *rparam)
124void (*release_appl)(struct capi_ctr *ctrlr, u16 applid)
125 pointers to callback functions for registration and deregistration of
126 applications with the device
127
128u16 (*send_message)(struct capi_ctr *ctrlr, struct sk_buff *skb)
129 pointer to a callback function for sending a CAPI message to the
130 device
131
132char *(*procinfo)(struct capi_ctr *ctrlr)
133 pointer to a callback function returning the entry for the device in
134 the CAPI controller info table, /proc/capi/controller
135
136read_proc_t *ctr_read_proc
137 pointer to the read_proc callback function for the device's proc file
138 system entry, /proc/capi/controllers/<n>; will be called with a
139 pointer to the device's capi_ctr structure as the last (data) argument
140
141- to be filled in before calling capi_ctr_ready():
142
143u8 manu[CAPI_MANUFACTURER_LEN]
144 value to return for CAPI_GET_MANUFACTURER
145
146capi_version version
147 value to return for CAPI_GET_VERSION
148
149capi_profile profile
150 value to return for CAPI_GET_PROFILE
151
152u8 serial[CAPI_SERIAL_LEN]
153 value to return for CAPI_GET_SERIAL
154
155
1565. Lower Layer Interface Functions
157
158(declared in <linux/isdn/capilli.h>)
159
160void register_capi_driver(struct capi_driver *drvr)
161void unregister_capi_driver(struct capi_driver *drvr)
162 register/unregister a driver with Kernel CAPI
163
164int attach_capi_ctr(struct capi_ctr *ctrlr)
165int detach_capi_ctr(struct capi_ctr *ctrlr)
166 register/unregister a device (controller) with Kernel CAPI
167
168void capi_ctr_ready(struct capi_ctr *ctrlr)
169void capi_ctr_reseted(struct capi_ctr *ctrlr)
170 signal controller ready/not ready
171
172void capi_ctr_suspend_output(struct capi_ctr *ctrlr)
173void capi_ctr_resume_output(struct capi_ctr *ctrlr)
174 signal suspend/resume
175
176void capi_ctr_handle_message(struct capi_ctr * ctrlr, u16 applid,
177 struct sk_buff *skb)
178 pass a received CAPI message to Kernel CAPI
179 for forwarding to the specified application
180
181
1826. Helper Functions and Macros
183
184Library functions (from <linux/isdn/capilli.h>):
185
186void capilib_new_ncci(struct list_head *head, u16 applid,
187 u32 ncci, u32 winsize)
188void capilib_free_ncci(struct list_head *head, u16 applid, u32 ncci)
189void capilib_release_appl(struct list_head *head, u16 applid)
190void capilib_release(struct list_head *head)
191void capilib_data_b3_conf(struct list_head *head, u16 applid,
192 u32 ncci, u16 msgid)
193u16 capilib_data_b3_req(struct list_head *head, u16 applid,
194 u32 ncci, u16 msgid)
195
196
197Macros to extract/set element values from/in a CAPI message header
198(from <linux/isdn/capiutil.h>):
199
200Get Macro Set Macro Element (Type)
201
202CAPIMSG_LEN(m) CAPIMSG_SETLEN(m, len) Total Length (u16)
203CAPIMSG_APPID(m) CAPIMSG_SETAPPID(m, applid) ApplID (u16)
204CAPIMSG_COMMAND(m) CAPIMSG_SETCOMMAND(m,cmd) Command (u8)
205CAPIMSG_SUBCOMMAND(m) CAPIMSG_SETSUBCOMMAND(m, cmd) Subcommand (u8)
206CAPIMSG_CMD(m) - Command*256
207 + Subcommand (u16)
208CAPIMSG_MSGID(m) CAPIMSG_SETMSGID(m, msgid) Message Number (u16)
209
210CAPIMSG_CONTROL(m) CAPIMSG_SETCONTROL(m, contr) Controller/PLCI/NCCI
211 (u32)
212CAPIMSG_DATALEN(m) CAPIMSG_SETDATALEN(m, len) Data Length (u16)
213