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isdn: extend INTERFACE.CAPI document

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Clarify calling context and return codes of callback methods, and
add a description of the _cmsg structure and helper functions.

Impact: documentation
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Tilman Schmidt 2009-06-07 09:09:24 +00:00 committed by David S. Miller
parent 7d31acda9f
commit fe93299a00
1 changed files with 88 additions and 2 deletions
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90
Documentation/isdn/INTERFACE.CAPI
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@ -114,20 +114,36 @@ char *driver_name
int (*load_firmware)(struct capi_ctr *ctrlr, capiloaddata *ldata)
(optional) pointer to a callback function for sending firmware and
configuration data to the device
Return value: 0 on success, error code on error
Called in process context.
void (*reset_ctr)(struct capi_ctr *ctrlr)
pointer to a callback function for performing a reset on the device,
releasing all registered applications
(optional) pointer to a callback function for performing a reset on
the device, releasing all registered applications
Called in process context.
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
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.
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
@ -138,6 +154,8 @@ read_proc_t *ctr_read_proc
system entry, /proc/capi/controllers/<n>; 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.
- to be filled in before calling capi_ctr_ready():
u8 manu[CAPI_MANUFACTURER_LEN]
@ -153,6 +171,45 @@ u8 serial[CAPI_SERIAL_LEN]
value to return for CAPI_GET_SERIAL
4.3 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, of
which only those 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' not containing any
variably-sized (struct) subparameters (eg. 'Called Party Number')
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.
_cmstruct for CAPI parameters of type 'struct' containing 'struct'
subparameters ('Additional Info' and 'B Protocol')
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
Functions capi_cmsg2message() and capi_message2cmsg() are provided to convert
messages between their transport encoding described in the CAPI 2.0 standard
and their _cmsg structure representation. Note that capi_cmsg2message() does
not know or check the size of its destination buffer. The caller must make
sure it is big enough to accomodate the resulting CAPI message.
5. Lower Layer Interface Functions
(declared in <linux/isdn/capilli.h>)
@ -211,3 +268,32 @@ 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>):
unsigned capi_cmsg2message(_cmsg *cmsg, u8 *msg)
Assembles a CAPI 2.0 message from the parameters in *cmsg, storing the
result in *msg.
unsigned capi_message2cmsg(_cmsg *cmsg, u8 *msg)
Disassembles the CAPI 2.0 message in *msg, storing the parameters in
*cmsg.
unsigned capi_cmsg_header(_cmsg *cmsg, u16 ApplId, u8 Command, u8 Subcommand,
u16 Messagenumber, u32 Controller)
Fills the header part and address field of the _cmsg structure *cmsg
with the given values, zeroing the remainder of the structure so only
parameters with non-default values need to be changed before sending
the message.
void capi_cmsg_answer(_cmsg *cmsg)
Sets the low bit of the Subcommand field in *cmsg, thereby converting
_REQ to _CONF and _IND to _RESP.
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.