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Commit fe93299a authored by Tilman Schmidt's avatar Tilman Schmidt Committed by David S. Miller
Browse files

isdn: extend INTERFACE.CAPI document 



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: default avatarTilman Schmidt <tilman@imap.cc>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7d31acda

Documentation/isdn/INTERFACE.CAPI

+88 −2
Original line number Diff line number Diff line
@@ -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.