tty: remove broken r3964 line discipline

Noone stepped up in the past two years since it was marked as BROKEN by
commit c7084edc (tty: mark Siemens R3964 line discipline as BROKEN).
Remove the line discipline for good.

Three remarks:
* we remove also the uapi header (as noone is able to use that interface
  anyway)
* we do *not* remove the N_R3964 constant definition from tty.h, so it
  remains reserved.
* in_interrupt() check is now removed from vt's con_put_char. Noone else
  calls tty_operations::put_char from interrupt context.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-2-jslaby@suse.czSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/powerpc/configs/ppc6xx_defconfig

@@ -621,7 +621,6 @@ CONFIG_HW_RANDOM=y
 CONFIG_HW_RANDOM_VIRTIO=m
 CONFIG_NVRAM=y
 CONFIG_DTLK=m
-CONFIG_R3964=m
 CONFIG_CARDMAN_4000=m
 CONFIG_CARDMAN_4040=m
 CONFIG_IPWIRELESS=m

drivers/char/Kconfig

@@ -218,19 +218,6 @@ config XILINX_HWICAP
 
 	  If unsure, say N.
 
-config R3964
-	tristate "Siemens R3964 line discipline"
-	depends on TTY && BROKEN
-	help
-	  This driver allows synchronous communication with devices using the
-	  Siemens R3964 packet protocol. Unless you are dealing with special
-	  hardware like PLCs, you are unlikely to need this.
-
-	  To compile this driver as a module, choose M here: the
-	  module will be called n_r3964.
-
-	  If unsure, say N.
-
 config APPLICOM
 	tristate "Applicom intelligent fieldbus card support"
 	depends on PCI

drivers/tty/Makefile

@@ -9,7 +9,6 @@ obj-$(CONFIG_AUDIT)		+= tty_audit.o
 obj-$(CONFIG_MAGIC_SYSRQ)	+= sysrq.o
 obj-$(CONFIG_N_HDLC)		+= n_hdlc.o
 obj-$(CONFIG_N_GSM)		+= n_gsm.o
-obj-$(CONFIG_R3964)		+= n_r3964.o
 
 obj-y				+= vt/
 obj-$(CONFIG_HVC_DRIVER)	+= hvc/

drivers/tty/vt/vt.c

@@ -3260,8 +3260,6 @@ static int con_write(struct tty_struct *tty, const unsigned char *buf, int count
 
 static int con_put_char(struct tty_struct *tty, unsigned char ch)
 {
-	if (in_interrupt())
-		return 0;	/* n_r3964 calls put_char() from interrupt context */
 	return do_con_write(tty, &ch, 1);
 }
 

include/linux/n_r3964.h

-/* r3964 linediscipline for linux
- *
- * -----------------------------------------------------------
- * Copyright by
- * Philips Automation Projects
- * Kassel (Germany)
- * -----------------------------------------------------------
- * This software may be used and distributed according to the terms of
- * the GNU General Public License, incorporated herein by reference.
- *
- * Author:
- * L. Haag
- *
- * $Log: r3964.h,v $
- * Revision 1.4  2005/12/21 19:54:24  Kurt Huwig <kurt huwig de>
- * Fixed HZ usage on 2.6 kernels
- * Removed unnecessary include
- *
- * Revision 1.3  2001/03/18 13:02:24  dwmw2
- * Fix timer usage, use spinlocks properly.
- *
- * Revision 1.2  2001/03/18 12:53:15  dwmw2
- * Merge changes in 2.4.2
- *
- * Revision 1.1.1.1  1998/10/13 16:43:14  dwmw2
- * This'll screw the version control
- *
- * Revision 1.6  1998/09/30 00:40:38  dwmw2
- * Updated to use kernel's N_R3964 if available
- *
- * Revision 1.4  1998/04/02 20:29:44  lhaag
- * select, blocking, ...
- *
- * Revision 1.3  1998/02/12 18:58:43  root
- * fixed some memory leaks
- * calculation of checksum characters
- *
- * Revision 1.2  1998/02/07 13:03:17  root
- * ioctl read_telegram
- *
- * Revision 1.1  1998/02/06 19:19:43  root
- * Initial revision
- *
- *
- */
-#ifndef __LINUX_N_R3964_H__
-#define __LINUX_N_R3964_H__
-
-
-#include <linux/param.h>
-#include <uapi/linux/n_r3964.h>
-
-/*
- * Common ascii handshake characters:
- */
-
-#define STX 0x02
-#define ETX 0x03
-#define DLE 0x10
-#define NAK 0x15
-
-/*
- * Timeouts (from milliseconds to jiffies)
- */
-
-#define R3964_TO_QVZ ((550)*HZ/1000)
-#define R3964_TO_ZVZ ((220)*HZ/1000)
-#define R3964_TO_NO_BUF ((400)*HZ/1000)
-#define R3964_NO_TX_ROOM ((100)*HZ/1000)
-#define R3964_TO_RX_PANIC ((4000)*HZ/1000)
-#define R3964_MAX_RETRIES 5
-
-
-enum { R3964_IDLE, 
-	   R3964_TX_REQUEST, R3964_TRANSMITTING, 
-	   R3964_WAIT_ZVZ_BEFORE_TX_RETRY, R3964_WAIT_FOR_TX_ACK,
-	   R3964_WAIT_FOR_RX_BUF,
-	   R3964_RECEIVING, R3964_WAIT_FOR_BCC, R3964_WAIT_FOR_RX_REPEAT
-	   };
-
-/*
- * All open file-handles are 'clients' and are stored in a linked list:
- */
-
-struct r3964_message;
-
-struct r3964_client_info {
-	spinlock_t     lock;
-	struct pid    *pid;
-	unsigned int   sig_flags;
-
-	struct r3964_client_info *next;
-
-	struct r3964_message *first_msg;
-	struct r3964_message *last_msg;
-	struct r3964_block_header *next_block_to_read;
-	int            msg_count;
-};
-
-
-
-struct r3964_block_header;
-
-/* internal version of client_message: */
-struct r3964_message {
-	  int     msg_id;
-	  int     arg;
-	  int     error_code;
-	  struct r3964_block_header *block;
-	  struct r3964_message *next;
-};
-
-/*
- * Header of received block in rx_buf/tx_buf:
- */
-
-struct r3964_block_header 
-{
-	unsigned int length;             /* length in chars without header */
-	unsigned char *data;             /* usually data is located 
-                                        immediately behind this struct */
-	unsigned int locks;              /* only used in rx_buffer */
-	  
-    struct r3964_block_header *next;
-	struct r3964_client_info *owner;  /* =NULL in rx_buffer */
-};
-
-/*
- * If rx_buf hasn't enough space to store R3964_MTU chars,
- * we will reject all incoming STX-requests by sending NAK.
- */
-
-#define RX_BUF_SIZE    4000
-#define TX_BUF_SIZE    4000
-#define R3964_MAX_BLOCKS_IN_RX_QUEUE 100
-
-#define R3964_PARITY 0x0001
-#define R3964_FRAME  0x0002
-#define R3964_OVERRUN 0x0004
-#define R3964_UNKNOWN 0x0008
-#define R3964_BREAK   0x0010
-#define R3964_CHECKSUM 0x0020
-#define R3964_ERROR  0x003f
-#define R3964_BCC   0x4000
-#define R3964_DEBUG 0x8000
-
-
-struct r3964_info {
-	spinlock_t     lock;
-	struct tty_struct *tty;
-	unsigned char priority;
-	unsigned char *rx_buf;            /* ring buffer */
-	unsigned char *tx_buf;
-
-	struct r3964_block_header *rx_first;
-	struct r3964_block_header *rx_last;
-	struct r3964_block_header *tx_first;
-	struct r3964_block_header *tx_last;
-	unsigned int tx_position;
-        unsigned int rx_position;
-	unsigned char last_rx;
-	unsigned char bcc;
-        unsigned int  blocks_in_rx_queue;
-
-	struct mutex read_lock;		/* serialize r3964_read */
-
-	struct r3964_client_info *firstClient;
-	unsigned int state;
-	unsigned int flags;
-
-	struct timer_list tmr;
-	int nRetry;
-};
-
-#endif

include/uapi/linux/n_r3964.h

-/* SPDX-License-Identifier: GPL-1.0+ WITH Linux-syscall-note */
-/* r3964 linediscipline for linux
- *
- * -----------------------------------------------------------
- * Copyright by
- * Philips Automation Projects
- * Kassel (Germany)
- * -----------------------------------------------------------
- * This software may be used and distributed according to the terms of
- * the GNU General Public License, incorporated herein by reference.
- *
- * Author:
- * L. Haag
- *
- * $Log: r3964.h,v $
- * Revision 1.4  2005/12/21 19:54:24  Kurt Huwig <kurt huwig de>
- * Fixed HZ usage on 2.6 kernels
- * Removed unnecessary include
- *
- * Revision 1.3  2001/03/18 13:02:24  dwmw2
- * Fix timer usage, use spinlocks properly.
- *
- * Revision 1.2  2001/03/18 12:53:15  dwmw2
- * Merge changes in 2.4.2
- *
- * Revision 1.1.1.1  1998/10/13 16:43:14  dwmw2
- * This'll screw the version control
- *
- * Revision 1.6  1998/09/30 00:40:38  dwmw2
- * Updated to use kernel's N_R3964 if available
- *
- * Revision 1.4  1998/04/02 20:29:44  lhaag
- * select, blocking, ...
- *
- * Revision 1.3  1998/02/12 18:58:43  root
- * fixed some memory leaks
- * calculation of checksum characters
- *
- * Revision 1.2  1998/02/07 13:03:17  root
- * ioctl read_telegram
- *
- * Revision 1.1  1998/02/06 19:19:43  root
- * Initial revision
- *
- *
- */
-
-#ifndef _UAPI__LINUX_N_R3964_H__
-#define _UAPI__LINUX_N_R3964_H__
-
-/* line disciplines for r3964 protocol */
-
-
-/*
- * Ioctl-commands
- */
-
-#define R3964_ENABLE_SIGNALS      0x5301
-#define R3964_SETPRIORITY         0x5302
-#define R3964_USE_BCC             0x5303
-#define R3964_READ_TELEGRAM       0x5304
-
-/* Options for R3964_SETPRIORITY */
-#define R3964_MASTER   0
-#define R3964_SLAVE    1
-
-/* Options for R3964_ENABLE_SIGNALS */
-#define R3964_SIG_ACK   0x0001
-#define R3964_SIG_DATA  0x0002
-#define R3964_SIG_ALL   0x000f
-#define R3964_SIG_NONE  0x0000
-#define R3964_USE_SIGIO 0x1000
-
-/*
- * r3964 operation states:
- */
-
-/* types for msg_id: */
-enum {R3964_MSG_ACK=1, R3964_MSG_DATA };
-
-#define R3964_MAX_MSG_COUNT 32
-
-/* error codes for client messages */
-#define R3964_OK 0        /* no error. */
-#define R3964_TX_FAIL -1  /* transmission error, block NOT sent */
-#define R3964_OVERFLOW -2 /* msg queue overflow */
-
-/* the client gets this struct when calling read(fd,...): */
-struct r3964_client_message {
-	  int     msg_id;
-	  int     arg;
-	  int     error_code;
-};
-
-#define R3964_MTU      256
-
-
-
-#endif /* _UAPI__LINUX_N_R3964_H__ */