isdn: capi: dead code removal

The staging isdn drivers are gone, and CONFIG_BT_CMTP is now
the only user. This means a lot of the code in the subsystem
has no remaining callers and can be removed.

Change the capi user space front-end to be part of kernelcapi,
and the combined module to only be compiled if BT_CMTP is
also enabled, then remove the interfaces that have no remaining
callers.

As the notifier list and the capi_drivers list have no callers
outside of kcapi.c, the implementation gets much simpler.

Some definitions from the include/linux/*.h headers are only
needed internally and are moved to kcapi.h.

Acked-by: David Miller <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Documentation/isdn/interface_capi.rst

@@ -26,13 +26,6 @@ This standard is freely available from https://www.capi.org.
 2. Driver and Device Registration
 =================================
 
-CAPI drivers optionally register themselves with Kernel CAPI by calling the
-Kernel CAPI function register_capi_driver() with a pointer to a struct
-capi_driver. This structure must be filled with the name and revision of the
-driver, and optionally a pointer to a callback function, add_card(). The
-registration can be revoked by calling the function unregister_capi_driver()
-with a pointer to the same struct capi_driver.
-
 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
@@ -89,9 +82,6 @@ register_capi_driver():
 	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
-``int (*add_card)(struct capi_driver *driver, capicardparams *data)``
-	a callback function pointer (may be NULL)
-
 
 4.2 struct capi_ctr
 -------------------
@@ -178,12 +168,6 @@ to be set by the driver before calling attach_capi_ctr():
 	pointer to a callback function returning the entry for the device in
 	the CAPI controller info table, /proc/capi/controller
 
-``const struct file_operations *proc_fops``
-	pointers to callback functions for the device's proc file
-	system entry, /proc/capi/controllers/<n>; pointer to the device's
-	capi_ctr structure is available from struct proc_dir_entry::data
-	which is available from struct inode.
-
 Note:
   Callback functions except send_message() are never called in interrupt
   context.
@@ -267,25 +251,10 @@ _cmstruct   alternative representation for CAPI parameters of type 'struct'
 	    _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 accommodate the resulting CAPI message.
-
 
 5. Lower Layer Interface Functions
 ==================================
 
-(declared in <linux/isdn/capilli.h>)
-
-::
-
-  void register_capi_driver(struct capi_driver *drvr)
-  void unregister_capi_driver(struct capi_driver *drvr)
-
-register/unregister a driver with Kernel CAPI
-
 ::
 
   int attach_capi_ctr(struct capi_ctr *ctrlr)
@@ -300,13 +269,6 @@ register/unregister a device (controller) with Kernel CAPI
 
 signal controller ready/not ready
 
-::
-
-  void capi_ctr_suspend_output(struct capi_ctr *ctrlr)
-  void capi_ctr_resume_output(struct capi_ctr *ctrlr)
-
-signal suspend/resume
-
 ::
 
   void capi_ctr_handle_message(struct capi_ctr * ctrlr, u16 applid,
@@ -319,21 +281,6 @@ for forwarding to the specified application
 6. Helper Functions and Macros
 ==============================
 
-Library functions (from <linux/isdn/capilli.h>):
-
-::
-
-  void capilib_new_ncci(struct list_head *head, u16 applid,
-			u32 ncci, u32 winsize)
-  void capilib_free_ncci(struct list_head *head, u16 applid, u32 ncci)
-  void capilib_release_appl(struct list_head *head, u16 applid)
-  void capilib_release(struct list_head *head)
-  void capilib_data_b3_conf(struct list_head *head, u16 applid,
-			u32 ncci, u16 msgid)
-  u16  capilib_data_b3_req(struct list_head *head, u16 applid,
-			u32 ncci, u16 msgid)
-
-
 Macros to extract/set element values from/in a CAPI message header
 (from <linux/isdn/capiutil.h>):
 
@@ -357,24 +304,6 @@ 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

drivers/isdn/Makefile

@@ -3,6 +3,6 @@
 
 # Object files in subdirectories
 
-obj-$(CONFIG_ISDN_CAPI)			+= capi/
+obj-$(CONFIG_BT_CMTP)			+= capi/
 obj-$(CONFIG_MISDN)			+= mISDN/
 obj-$(CONFIG_ISDN)			+= hardware/

drivers/isdn/capi/Kconfig

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-only
-menuconfig ISDN_CAPI
-	tristate "CAPI 2.0 subsystem"
+config ISDN_CAPI
+	def_bool ISDN && BT
 	help
 	  This provides CAPI (the Common ISDN Application Programming
 	  Interface) Version 2.0, a standard making it easy for programs to
@@ -15,42 +15,18 @@ menuconfig ISDN_CAPI
 	  See CONFIG_BT_CMTP for the last remaining regular driver
 	  in the kernel that uses the CAPI subsystem.
 
-if ISDN_CAPI
-
 config CAPI_TRACE
-	bool "CAPI trace support"
-	default y
+	def_bool BT_CMTP
 	help
 	  If you say Y here, the kernelcapi driver can make verbose traces
 	  of CAPI messages. This feature can be enabled/disabled via IOCTL for
 	  every controller (default disabled).
-	  This will increase the size of the kernelcapi module by 20 KB.
-	  If unsure, say Y.
-
-config ISDN_CAPI_CAPI20
-	tristate "CAPI2.0 /dev/capi20 support"
-	help
-	  This option will provide the CAPI 2.0 interface to userspace
-	  applications via /dev/capi20. Applications should use the
-	  standardized libcapi20 to access this functionality.  You should say
-	  Y/M here.
 
 config ISDN_CAPI_MIDDLEWARE
-	bool "CAPI2.0 Middleware support"
-	depends on ISDN_CAPI_CAPI20 && TTY
+	def_bool BT_CMTP && TTY
 	help
 	  This option will enhance the capabilities of the /dev/capi20
 	  interface.  It will provide a means of moving a data connection,
 	  established via the usual /dev/capi20 interface to a special tty
 	  device.  If you want to use pppd with pppdcapiplugin to dial up to
 	  your ISP, say Y here.
-
-config ISDN_CAPI_CAPIDRV_VERBOSE
-	bool "Verbose reason code reporting"
-	depends on ISDN_CAPI_CAPIDRV
-	help
-	  If you say Y here, the capidrv interface will give verbose reasons
-	  for disconnecting. This will increase the size of the kernel by 7 KB.
-	  If unsure, say N.
-
-endif

drivers/isdn/capi/Makefile

@@ -1,17 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-# Makefile for the CAPI subsystem.
+# Makefile for the CAPI subsystem used by BT_CMTP
 
-# Ordering constraints: kernelcapi.o first
-
-# Each configuration option enables a list of files.
-
-obj-$(CONFIG_ISDN_CAPI)			+= kernelcapi.o
-obj-$(CONFIG_ISDN_CAPI_CAPI20)		+= capi.o 
-obj-$(CONFIG_ISDN_CAPI_CAPIDRV)		+= capidrv.o
-
-# Multipart objects.
-
-kernelcapi-y				:= kcapi.o capiutil.o capilib.o
-kernelcapi-$(CONFIG_PROC_FS)		+= kcapi_proc.o
-
-ccflags-y += -I$(srctree)/$(src)/../include -I$(srctree)/$(src)/../include/uapi
+obj-$(CONFIG_BT_CMTP)			+= kernelcapi.o
+kernelcapi-y				:= kcapi.o capiutil.o capi.o kcapi_proc.o

drivers/isdn/capi/capi.c

@@ -39,7 +39,9 @@
 #include <linux/isdn/capiutil.h>
 #include <linux/isdn/capicmd.h>
 
-MODULE_DESCRIPTION("CAPI4Linux: Userspace /dev/capi20 interface");
+#include "kcapi.h"
+
+MODULE_DESCRIPTION("CAPI4Linux: kernel CAPI layer and /dev/capi20 interface");
 MODULE_AUTHOR("Carsten Paeth");
 MODULE_LICENSE("GPL");
 
@@ -1412,15 +1414,22 @@ static int __init capi_init(void)
 {
 	const char *compileinfo;
 	int major_ret;
+	int ret;
+
+	ret = kcapi_init();
+	if (ret)
+		return ret;
 
 	major_ret = register_chrdev(capi_major, "capi20", &capi_fops);
 	if (major_ret < 0) {
 		printk(KERN_ERR "capi20: unable to get major %d\n", capi_major);
+		kcapi_exit();
 		return major_ret;
 	}
 	capi_class = class_create(THIS_MODULE, "capi");
 	if (IS_ERR(capi_class)) {
 		unregister_chrdev(capi_major, "capi20");
+		kcapi_exit();
 		return PTR_ERR(capi_class);
 	}
 
@@ -1430,6 +1439,7 @@ static int __init capi_init(void)
 		device_destroy(capi_class, MKDEV(capi_major, 0));
 		class_destroy(capi_class);
 		unregister_chrdev(capi_major, "capi20");
+		kcapi_exit();
 		return -ENOMEM;
 	}
 
@@ -1455,6 +1465,8 @@ static void __exit capi_exit(void)
 	unregister_chrdev(capi_major, "capi20");
 
 	capinc_tty_exit();
+
+	kcapi_exit();
 }
 
 module_init(capi_init);