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authorTilman Schmidt <tilman@imap.cc>2009-06-07 09:09:24 +0000
committerDavid S. Miller <davem@davemloft.net>2009-06-08 00:45:52 -0700
commitfe93299a008a7056fe1790744b3a425ddf79a16b (patch)
tree918460120177a3ab1a79f28f4409ead19f7a39dc /Documentation/isdn
parent7d31acda9f8eaa27e2fd232712f7e1f3e9a79bdb (diff)
downloadlinux-fe93299a008a7056fe1790744b3a425ddf79a16b.tar.gz
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: Tilman Schmidt <tilman@imap.cc> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/isdn')
-rw-r--r--Documentation/isdn/INTERFACE.CAPI90
1 files changed, 88 insertions, 2 deletions
diff --git a/Documentation/isdn/INTERFACE.CAPI b/Documentation/isdn/INTERFACE.CAPI
index 46315381616..686e107923e 100644
--- a/Documentation/isdn/INTERFACE.CAPI
+++ b/Documentation/isdn/INTERFACE.CAPI
@@ -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.
+