[PATCH] s390: vt220 console.

Add support for vt220 console over sclp.

arch/s390/defconfig

@@ -137,6 +137,7 @@ CONFIG_CCW_CONSOLE=y
 CONFIG_SCLP=y
 CONFIG_SCLP_TTY=y
 CONFIG_SCLP_CONSOLE=y
+# CONFIG_SCLP_VT220_TTY is not set
 CONFIG_SCLP_CPI=m
 CONFIG_S390_TAPE=m
 

drivers/s390/Kconfig

@@ -101,6 +101,19 @@ config SCLP_CONSOLE
 	  Include support for using an IBM HWC line-mode terminal as the Linux
 	  system console.
 
+config SCLP_VT220_TTY
+	bool "Support for SCLP VT220-compatible terminal"
+	depends on SCLP
+	help
+	  Include support for an IBM SCLP VT220-compatible terminal.
+
+config SCLP_VT220_CONSOLE
+	bool "Support for console on SCLP VT220-compatible terminal"
+	depends on SCLP_VT220_TTY
+	help
+	  Include support for using an IBM SCLP VT220-compatible terminal as a
+	  Linux system console.
+
 config SCLP_CPI
 	tristate "Control-Program Identification"
 	depends on SCLP

drivers/s390/char/Makefile

@@ -11,6 +11,7 @@ obj-$(CONFIG_TN3215) += con3215.o
 obj-$(CONFIG_SCLP) += sclp.o sclp_rw.o
 obj-$(CONFIG_SCLP_TTY) += sclp_tty.o
 obj-$(CONFIG_SCLP_CONSOLE) += sclp_con.o
+obj-$(CONFIG_SCLP_VT220_TTY) += sclp_vt220.o
 obj-$(CONFIG_SCLP_CPI) += sclp_cpi.o
 obj-$(CONFIG_TN3270) += tub3270.o
 tape-$(CONFIG_S390_TAPE_BLOCK) += tape_block.o

drivers/s390/char/sclp.h

@@ -26,6 +26,7 @@
 #define EvTyp_CntlProgOpCmd	0x20
 #define EvTyp_CntlProgIdent	0x0B
 #define EvTyp_SigQuiesce	0x1D
+#define EvTyp_VT220Msg		0x1A
 
 #define EvTyp_OpCmd_Mask	0x80000000
 #define EvTyp_Msg_Mask		0x40000000
@@ -34,6 +35,7 @@
 #define EvTyp_CtlProgOpCmd_Mask	0x00000001
 #define EvTyp_CtlProgIdent_Mask	0x00200000
 #define EvTyp_SigQuiesce_Mask	0x00000008
+#define EvTyp_VT220Msg_Mask	0x00000040
 
 #define GnrlMsgFlgs_DOM		0x8000
 #define GnrlMsgFlgs_SndAlrm	0x4000

drivers/s390/char/sclp_cpi.c

@@ -9,6 +9,7 @@
 #include <linux/version.h>
 #include <linux/kmod.h>
 #include <linux/module.h>
+#include <linux/moduleparam.h>
 #include <linux/init.h>
 #include <linux/timer.h>
 #include <linux/string.h>
@@ -58,12 +59,12 @@ MODULE_DESCRIPTION(
 	"or zSeries hardware");
 
 static char *system_name = NULL;
-MODULE_PARM(system_name, "s");
+module_param(system_name, charp, 0);
 MODULE_PARM_DESC(system_name, "e.g. hostname - max. 8 characters");
 
 static char *sysplex_name = NULL;
 #ifdef ALLOW_SYSPLEX_NAME
-MODULE_PARM(sysplex_name, "s");
+module_param(sysplex_name, charp, 0);
 MODULE_PARM_DESC(sysplex_name, "if applicable - max. 8 characters");
 #endif
 

drivers/s390/char/sclp_tty.c

@@ -779,7 +779,7 @@ sclp_tty_init(void)
 
 	driver->owner = THIS_MODULE;
 	driver->driver_name = "sclp_line";
-	driver->name = "ttyS";
+	driver->name = "sclp_line";
 	driver->major = TTY_MAJOR;
 	driver->minor_start = 64;
 	driver->type = TTY_DRIVER_TYPE_SYSTEM;

drivers/s390/char/sclp_vt220.c

+/*
+ *  drivers/s390/char/sclp_vt220.c
+ *    SCLP VT220 terminal driver.
+ *
+ *  S390 version
+ *    Copyright (C) 2003 IBM Deutschland Entwicklung GmbH, IBM Corporation
+ *    Author(s): Peter Oberparleiter <Peter.Oberparleiter@de.ibm.com>
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/list.h>
+#include <linux/wait.h>
+#include <linux/timer.h>
+#include <linux/kernel.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/sched.h>
+#include <linux/errno.h>
+#include <linux/mm.h>
+#include <linux/major.h>
+#include <linux/console.h>
+#include <linux/kdev_t.h>
+#include <linux/bootmem.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <asm/uaccess.h>
+#include "sclp.h"
+
+#define SCLP_VT220_PRINT_HEADER 	"sclp vt220 tty driver: "
+#define SCLP_VT220_MAJOR		TTY_MAJOR
+#define SCLP_VT220_MINOR		65
+#define SCLP_VT220_DRIVER_NAME		"sclp_vt220"
+#define SCLP_VT220_DEVICE_NAME		"sclp_vt"
+#define SCLP_VT220_CONSOLE_NAME		"ttyS"
+#define SCLP_VT220_CONSOLE_INDEX	1	/* console=ttyS1 */
+
+/* Representation of a single write request */
+struct sclp_vt220_request {
+	struct list_head list;
+	struct sclp_req sclp_req;
+	int retry_count;
+	struct timer_list retry_timer;
+};
+
+/* VT220 SCCB */
+struct sclp_vt220_sccb {
+	struct sccb_header header;
+	struct evbuf_header evbuf;
+};
+
+#define SCLP_VT220_MAX_CHARS_PER_BUFFER	(PAGE_SIZE - \
+					 sizeof(struct sclp_vt220_request) - \
+					 sizeof(struct sclp_vt220_sccb))
+
+/* Structures and data needed to register tty driver */
+static struct tty_driver *sclp_vt220_driver;
+
+/* The tty_struct that the kernel associated with us */
+static struct tty_struct *sclp_vt220_tty;
+
+/* Lock to protect internal data from concurrent access */
+static spinlock_t sclp_vt220_lock;
+
+/* List of empty pages to be used as write request buffers */
+static struct list_head sclp_vt220_empty;
+
+/* List of pending requests */
+static struct list_head sclp_vt220_outqueue;
+
+/* Number of requests in outqueue */
+static int sclp_vt220_outqueue_count;
+
+/* Wait queue used to delay write requests while we've run out of buffers */
+static wait_queue_head_t sclp_vt220_waitq;
+
+/* Timer used for delaying write requests to merge subsequent messages into
+ * a single buffer */
+static struct timer_list sclp_vt220_timer;
+
+/* Pointer to current request buffer which has been partially filled but not
+ * yet sent */
+static struct sclp_vt220_request *sclp_vt220_current_request;
+
+/* Number of characters in current request buffer */
+static int sclp_vt220_buffered_chars;
+
+/* Flag indicating whether this driver has already been initialized */
+static int sclp_vt220_initialized = 0;
+
+/* Flag indicating that sclp_vt220_current_request should really
+ * have been already queued but wasn't because the SCLP was processing
+ * another buffer */
+static int sclp_vt220_flush_later;
+
+static void sclp_vt220_receiver_fn(struct evbuf_header *evbuf);
+static void __sclp_vt220_emit(struct sclp_vt220_request *request);
+static void sclp_vt220_emit_current(void);
+
+/* Registration structure for our interest in SCLP event buffers */
+static struct sclp_register sclp_vt220_register = {
+	.send_mask		= EvTyp_VT220Msg_Mask,
+	.receive_mask		= EvTyp_VT220Msg_Mask,
+	.state_change_fn	= NULL,
+	.receiver_fn		= sclp_vt220_receiver_fn
+};
+
+
+/*
+ * Put provided request buffer back into queue and check emit pending
+ * buffers if necessary.
+ */
+static void
+sclp_vt220_process_queue(struct sclp_vt220_request *request)
+{
+	unsigned long flags;
+	struct sclp_vt220_request *next;
+	void *page;
+
+	/* Put buffer back to list of empty buffers */
+	page = request->sclp_req.sccb;
+	spin_lock_irqsave(&sclp_vt220_lock, flags);
+	/* Move request from outqueue to empty queue */
+	list_del(&request->list);
+	sclp_vt220_outqueue_count--;
+	list_add_tail((struct list_head *) page, &sclp_vt220_empty);
+	/* Check if there is a pending buffer on the out queue. */
+	next = NULL;
+	if (!list_empty(&sclp_vt220_outqueue))
+		next = list_entry(sclp_vt220_outqueue.next,
+				  struct sclp_vt220_request, list);
+	spin_unlock_irqrestore(&sclp_vt220_lock, flags);
+	if (next != NULL)
+		__sclp_vt220_emit(next);
+	else if (sclp_vt220_flush_later)
+		sclp_vt220_emit_current();
+	wake_up(&sclp_vt220_waitq);
+	/* Check if the tty needs a wake up call */
+	if (sclp_vt220_tty != NULL) {
+		if ((sclp_vt220_tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&
+		    (sclp_vt220_tty->ldisc.write_wakeup != NULL))
+			(sclp_vt220_tty->ldisc.write_wakeup)(sclp_vt220_tty);
+		wake_up_interruptible(&sclp_vt220_tty->write_wait);
+	}
+}
+
+/*
+ * Retry sclp write request after waiting some time for an sclp equipment
+ * check to pass.
+ */
+static void
+sclp_vt220_retry(unsigned long data)
+{
+	struct sclp_vt220_request *request;
+	struct sclp_vt220_sccb *sccb;
+
+	request = (struct sclp_vt220_request *) data;
+	request->sclp_req.status = SCLP_REQ_FILLED;
+	sccb = (struct sclp_vt220_sccb *) request->sclp_req.sccb;
+	sccb->header.response_code = 0x0000;
+	sclp_add_request(&request->sclp_req);
+}
+
+#define SCLP_BUFFER_MAX_RETRY		5
+#define	SCLP_BUFFER_RETRY_INTERVAL	2
+
+/*
+ * Callback through which the result of a write request is reported by the
+ * SCLP.
+ */
+static void
+sclp_vt220_callback(struct sclp_req *request, void *data)
+{
+	struct sclp_vt220_request *vt220_request;
+	struct sclp_vt220_sccb *sccb;
+
+	vt220_request = (struct sclp_vt220_request *) data;
+	if (request->status == SCLP_REQ_FAILED) {
+		sclp_vt220_process_queue(vt220_request);
+		return;
+	}
+	sccb = (struct sclp_vt220_sccb *) vt220_request->sclp_req.sccb;
+
+	/* Check SCLP response code and choose suitable action	*/
+	switch (sccb->header.response_code) {
+	case 0x0020 :
+		break;
+
+	case 0x05f0: /* Target resource in improper state */
+		break;
+
+	case 0x0340: /* Contained SCLP equipment check */
+		if (vt220_request->retry_count++ > SCLP_BUFFER_MAX_RETRY)
+			break;
+		/* Remove processed buffers and requeue rest */
+		if (sclp_remove_processed((struct sccb_header *) sccb) > 0) {
+			/* Not all buffers were processed */
+			sccb->header.response_code = 0x0000;
+			vt220_request->sclp_req.status = SCLP_REQ_FILLED;
+			sclp_add_request(request);
+			return;
+		}
+		break;
+
+	case 0x0040: /* SCLP equipment check */
+		if (vt220_request->retry_count++ > SCLP_BUFFER_MAX_RETRY)
+			break;
+		/* Wait some time, then retry request */
+		vt220_request->retry_timer.function = sclp_vt220_retry;
+		vt220_request->retry_timer.data =
+			(unsigned long) vt220_request;
+		vt220_request->retry_timer.expires =
+			jiffies + SCLP_BUFFER_RETRY_INTERVAL*HZ;
+		add_timer(&vt220_request->retry_timer);
+		return;
+
+	default:
+		break;
+	}
+	sclp_vt220_process_queue(vt220_request);
+}
+
+/*
+ * Emit vt220 request buffer to SCLP.
+ */
+static void
+__sclp_vt220_emit(struct sclp_vt220_request *request)
+{
+	if (!(sclp_vt220_register.sclp_send_mask & EvTyp_VT220Msg_Mask)) {
+		request->sclp_req.status = SCLP_REQ_FAILED;
+		sclp_vt220_callback(&request->sclp_req, (void *) request);
+		return;
+	}
+	request->sclp_req.command = SCLP_CMDW_WRITEDATA;
+	request->sclp_req.status = SCLP_REQ_FILLED;
+	request->sclp_req.callback = sclp_vt220_callback;
+	request->sclp_req.callback_data = (void *) request;
+
+	sclp_add_request(&request->sclp_req);
+}
+
+/*
+ * Queue and emit given request.
+ */
+static void
+sclp_vt220_emit(struct sclp_vt220_request *request)
+{
+	unsigned long flags;
+	int count;
+
+	spin_lock_irqsave(&sclp_vt220_lock, flags);
+	list_add_tail(&request->list, &sclp_vt220_outqueue);
+	count = sclp_vt220_outqueue_count++;
+	spin_unlock_irqrestore(&sclp_vt220_lock, flags);
+	/* Emit only the first buffer immediately - callback takes care of
+	 * the rest */
+	if (count == 0)
+		__sclp_vt220_emit(request);
+}
+
+/*
+ * Queue and emit current request.
+ */
+static void
+sclp_vt220_emit_current(void)
+{
+	unsigned long flags;
+	struct sclp_vt220_request *request;
+	struct sclp_vt220_sccb *sccb;
+
+	spin_lock_irqsave(&sclp_vt220_lock, flags);
+	request = NULL;
+	if (sclp_vt220_current_request != NULL) {
+		sccb = (struct sclp_vt220_sccb *) 
+				sclp_vt220_current_request->sclp_req.sccb;
+		/* Only emit buffers with content */
+		if (sccb->header.length != sizeof(struct sclp_vt220_sccb)) {
+			request = sclp_vt220_current_request;
+			sclp_vt220_current_request = NULL;
+			if (timer_pending(&sclp_vt220_timer))
+				del_timer(&sclp_vt220_timer);
+		}
+		sclp_vt220_flush_later = 0;
+	}
+	spin_unlock_irqrestore(&sclp_vt220_lock, flags);
+	if (request != NULL)
+		sclp_vt220_emit(request);
+}
+
+#define SCLP_NORMAL_WRITE	0x00
+
+/*
+ * Helper function to initialize a page with the sclp request structure.
+ */
+static struct sclp_vt220_request *
+sclp_vt220_initialize_page(void *page)
+{
+	struct sclp_vt220_request *request;
+	struct sclp_vt220_sccb *sccb;
+
+	/* Place request structure at end of page */
+	request = ((struct sclp_vt220_request *)
+			((addr_t) page + PAGE_SIZE)) - 1;
+	init_timer(&request->retry_timer);
+	request->retry_count = 0;
+	request->sclp_req.sccb = page;
+	/* SCCB goes at start of page */
+	sccb = (struct sclp_vt220_sccb *) page;
+	memset((void *) sccb, 0, sizeof(struct sclp_vt220_sccb));
+	sccb->header.length = sizeof(struct sclp_vt220_sccb);
+	sccb->header.function_code = SCLP_NORMAL_WRITE;
+	sccb->header.response_code = 0x0000;
+	sccb->evbuf.type = EvTyp_VT220Msg;
+	sccb->evbuf.length = sizeof(struct evbuf_header);
+
+	return request;
+}
+
+static inline unsigned int
+sclp_vt220_space_left(struct sclp_vt220_request *request)
+{
+	struct sclp_vt220_sccb *sccb;
+	sccb = (struct sclp_vt220_sccb *) request->sclp_req.sccb;
+	return PAGE_SIZE - sizeof(struct sclp_vt220_request) -
+	       sccb->header.length;
+}
+
+static inline unsigned int
+sclp_vt220_chars_stored(struct sclp_vt220_request *request)
+{
+	struct sclp_vt220_sccb *sccb;
+	sccb = (struct sclp_vt220_sccb *) request->sclp_req.sccb;
+	return sccb->evbuf.length - sizeof(struct evbuf_header);
+}
+
+/*
+ * Add msg to buffer associated with request. Return the number of characters
+ * added or -EFAULT on error.
+ */
+static int
+sclp_vt220_add_msg(struct sclp_vt220_request *request,
+		   const unsigned char *msg, int count, int from_user,
+		   int convertlf)
+{
+	struct sclp_vt220_sccb *sccb;
+	void *buffer;
+	unsigned char c;
+	int from;
+	int to;
+
+	if (count > sclp_vt220_space_left(request))
+		count = sclp_vt220_space_left(request);
+	if (count <= 0)
+		return 0;
+
+	sccb = (struct sclp_vt220_sccb *) request->sclp_req.sccb;
+	buffer = (void *) ((addr_t) sccb + sccb->header.length);
+
+	if (convertlf) {
+		/* Perform Linefeed conversion (0x0a -> 0x0a 0x0d)*/
+		for (from=0, to=0;
+		     (from < count) && (to < sclp_vt220_space_left(request));
+		     from++) {
+			/* Retrieve character */
+			if (from_user) {
+				if (get_user(c, msg + from) != 0)
+					return -EFAULT;
+			} else
+				c = msg[from];
+			/* Perform conversion */
+			if (c == 0x0a) {
+				if (to + 1 < sclp_vt220_space_left(request)) {
+					((unsigned char *) buffer)[to++] = c;
+					((unsigned char *) buffer)[to++] = 0x0d;
+				} else
+					break;
+
+			} else
+				((unsigned char *) buffer)[to++] = c;
+		}
+		sccb->header.length += to;
+		sccb->evbuf.length += to;
+		return from;
+	} else {
+		if (from_user) {
+			if (copy_from_user(buffer, (void *) msg, count) != 0)
+				return -EFAULT;
+		}
+		else
+			memcpy(buffer, (const void *) msg, count);
+		sccb->header.length += count;
+		sccb->evbuf.length += count;
+		return count;
+	}
+}
+
+/*
+ * Emit buffer after having waited long enough for more data to arrive.
+ */
+static void
+sclp_vt220_timeout(unsigned long data)
+{
+	sclp_vt220_emit_current();
+}
+
+#define BUFFER_MAX_DELAY	HZ/2
+
+/* 
+ * Internal implementation of the write function. Write COUNT bytes of data
+ * from memory at BUF which may reside in user space (specified by FROM_USER)
+ * to the SCLP interface. In case that the data does not fit into the current
+ * write buffer, emit the current one and allocate a new one. If there are no
+ * more empty buffers available, wait until one gets emptied. If DO_SCHEDULE
+ * is non-zero, the buffer will be scheduled for emitting after a timeout -
+ * otherwise the user has to explicitly call the flush function.
+ * A non-zero CONVERTLF parameter indicates that 0x0a characters in the message
+ * buffer should be converted to 0x0a 0x0d. After completion, return the number
+ * of bytes written.
+ */
+static int
+__sclp_vt220_write(int from_user, const unsigned char *buf, int count,
+		   int do_schedule, int convertlf)
+{
+	unsigned long flags;
+	void *page;
+	int written;
+	int overall_written;
+
+	if (count <= 0)
+		return 0;
+	overall_written = 0;
+	spin_lock_irqsave(&sclp_vt220_lock, flags);
+	do {
+		/* Create a sclp output buffer if none exists yet */
+		if (sclp_vt220_current_request == NULL) {
+			while (list_empty(&sclp_vt220_empty)) {
+				spin_unlock_irqrestore(&sclp_vt220_lock,
+						       flags);
+				if (in_interrupt())
+					sclp_sync_wait();
+				else
+					wait_event(sclp_vt220_waitq,
+						!list_empty(&sclp_vt220_empty));
+				spin_lock_irqsave(&sclp_vt220_lock, flags);
+			}
+			page = (void *) sclp_vt220_empty.next;
+			list_del((struct list_head *) page);
+			sclp_vt220_current_request =
+				sclp_vt220_initialize_page(page);
+		}
+		/* Try to write the string to the current request buffer */
+		written = sclp_vt220_add_msg(sclp_vt220_current_request,
+				buf, count, from_user, convertlf);
+		if (written > 0)
+			overall_written += written;
+		if (written == -EFAULT || written == count)
+			break;
+		/*
+		 * Not all characters could be written to the current
+		 * output buffer. Emit the buffer, create a new buffer
+		 * and then output the rest of the string.
+		 */
+		spin_unlock_irqrestore(&sclp_vt220_lock, flags);
+		sclp_vt220_emit_current();
+		spin_lock_irqsave(&sclp_vt220_lock, flags);
+		buf += written;
+		count -= written;
+	} while (count > 0);
+	/* Setup timer to output current console buffer after some time */
+	if (sclp_vt220_current_request != NULL &&
+	    !timer_pending(&sclp_vt220_timer) && do_schedule) {
+		sclp_vt220_timer.function = sclp_vt220_timeout;
+		sclp_vt220_timer.data = 0UL;
+		sclp_vt220_timer.expires = jiffies + BUFFER_MAX_DELAY;
+		add_timer(&sclp_vt220_timer);
+	}
+	spin_unlock_irqrestore(&sclp_vt220_lock, flags);
+	return overall_written;
+}
+
+/*
+ * This routine is called by the kernel to write a series of
+ * characters to the tty device.  The characters may come from
+ * user space or kernel space.  This routine will return the
+ * number of characters actually accepted for writing.
+ */
+static int
+sclp_vt220_write(struct tty_struct *tty, int from_user,
+		 const unsigned char *buf, int count)
+{
+	return __sclp_vt220_write(from_user, buf, count, 1, 0);
+}
+
+#define SCLP_VT220_SESSION_ENDED	0x01
+#define	SCLP_VT220_SESSION_STARTED	0x80
+#define SCLP_VT220_SESSION_DATA		0x00
+
+/*
+ * Called by the SCLP to report incoming event buffers.
+ */
+static void
+sclp_vt220_receiver_fn(struct evbuf_header *evbuf)
+{
+	char *buffer;
+	unsigned int count;
+
+	/* Ignore input if device is not open */
+	if (sclp_vt220_tty == NULL)
+		return;
+
+	buffer = (char *) ((addr_t) evbuf + sizeof(struct evbuf_header));
+	count = evbuf->length - sizeof(struct evbuf_header);
+
+	switch (*buffer) {
+	case SCLP_VT220_SESSION_ENDED:
+	case SCLP_VT220_SESSION_STARTED:
+		break;
+	case SCLP_VT220_SESSION_DATA:
+		/* Send input to line discipline */
+		buffer++;
+		count--;
+		/* Prevent buffer overrun by discarding input. Note that
+		 * because buffer_push works asynchronously, we cannot wait
+		 * for the buffer to be emptied. */
+		if (count + sclp_vt220_tty->flip.count > TTY_FLIPBUF_SIZE)
+			count = TTY_FLIPBUF_SIZE - sclp_vt220_tty->flip.count;
+		memcpy(sclp_vt220_tty->flip.char_buf_ptr, buffer, count);
+		memset(sclp_vt220_tty->flip.flag_buf_ptr, TTY_NORMAL, count);
+		sclp_vt220_tty->flip.char_buf_ptr += count;
+		sclp_vt220_tty->flip.flag_buf_ptr += count;
+		sclp_vt220_tty->flip.count += count;
+		tty_flip_buffer_push(sclp_vt220_tty);
+		break;
+	}
+}
+
+/*
+ * This routine is called when a particular tty device is opened.
+ */
+static int
+sclp_vt220_open(struct tty_struct *tty, struct file *filp)
+{
+	sclp_vt220_tty = tty;
+	tty->driver_data = NULL;
+	tty->low_latency = 0;
+	return 0;
+}
+
+/*
+ * This routine is called when a particular tty device is closed.
+ */
+static void
+sclp_vt220_close(struct tty_struct *tty, struct file *filp)
+{
+	if (tty->count > 1)
+		return;
+	sclp_vt220_tty = NULL;
+}
+
+/*
+ * This routine is called by the kernel to write a single
+ * character to the tty device.  If the kernel uses this routine,
+ * it must call the flush_chars() routine (if defined) when it is
+ * done stuffing characters into the driver.
+ *
+ * NOTE: include/linux/tty_driver.h specifies that a character should be
+ * ignored if there is no room in the queue. This driver implements a different
+ * semantic in that it will block when there is no more room left.
+ */
+static void
+sclp_vt220_put_char(struct tty_struct *tty, unsigned char ch)
+{
+	__sclp_vt220_write(0, &ch, 1, 0, 0);
+}
+
+/*
+ * This routine is called by the kernel after it has written a
+ * series of characters to the tty device using put_char().  
+ */
+static void
+sclp_vt220_flush_chars(struct tty_struct *tty)
+{
+	if (sclp_vt220_outqueue_count == 0)
+		sclp_vt220_emit_current();
+	else
+		sclp_vt220_flush_later = 1;
+}
+
+/*
+ * This routine returns the numbers of characters the tty driver
+ * will accept for queuing to be written.  This number is subject
+ * to change as output buffers get emptied, or if the output flow
+ * control is acted.
+ */
+static int
+sclp_vt220_write_room(struct tty_struct *tty)
+{
+	unsigned long flags;
+	struct list_head *l;
+	int count;
+
+	spin_lock_irqsave(&sclp_vt220_lock, flags);
+	count = 0;
+	if (sclp_vt220_current_request != NULL)
+		count = sclp_vt220_space_left(sclp_vt220_current_request);
+	list_for_each(l, &sclp_vt220_empty)
+		count += SCLP_VT220_MAX_CHARS_PER_BUFFER;
+	spin_unlock_irqrestore(&sclp_vt220_lock, flags);
+	return count;
+}
+
+/*
+ * Return number of buffered chars.
+ */
+static int
+sclp_vt220_chars_in_buffer(struct tty_struct *tty)
+{
+	unsigned long flags;
+	struct list_head *l;
+	struct sclp_vt220_request *r;
+	int count;
+
+	spin_lock_irqsave(&sclp_vt220_lock, flags);
+	count = 0;
+	if (sclp_vt220_current_request != NULL)
+		count = sclp_vt220_chars_stored(sclp_vt220_current_request);
+	list_for_each(l, &sclp_vt220_outqueue) {
+		r = list_entry(l, struct sclp_vt220_request, list);
+		count += sclp_vt220_chars_stored(r);
+	}
+	spin_unlock_irqrestore(&sclp_vt220_lock, flags);
+	return count;
+}
+
+static void
+__sclp_vt220_flush_buffer(void)
+{
+	unsigned long flags;
+
+	sclp_vt220_emit_current();
+	spin_lock_irqsave(&sclp_vt220_lock, flags);
+	if (timer_pending(&sclp_vt220_timer))
+		del_timer(&sclp_vt220_timer);
+	while (sclp_vt220_outqueue_count > 0) {
+		spin_unlock_irqrestore(&sclp_vt220_lock, flags);
+		sclp_sync_wait();
+		spin_lock_irqsave(&sclp_vt220_lock, flags);
+	}
+	spin_unlock_irqrestore(&sclp_vt220_lock, flags);
+}
+
+/*
+ * Pass on all buffers to the hardware. Return only when there are no more
+ * buffers pending.
+ */
+static void
+sclp_vt220_flush_buffer(struct tty_struct *tty)
+{
+	sclp_vt220_emit_current();
+}
+
+/*
+ * Initialize all relevant components and register driver with system.
+ */
+static int
+__sclp_vt220_init(int early)
+{
+	void *page;
+	int i;
+
+	if (sclp_vt220_initialized)
+		return 0;
+	sclp_vt220_initialized = 1;
+	spin_lock_init(&sclp_vt220_lock);
+	INIT_LIST_HEAD(&sclp_vt220_empty);
+	INIT_LIST_HEAD(&sclp_vt220_outqueue);
+	init_waitqueue_head(&sclp_vt220_waitq);
+	init_timer(&sclp_vt220_timer);
+	sclp_vt220_current_request = NULL;
+	sclp_vt220_buffered_chars = 0;
+	sclp_vt220_outqueue_count = 0;
+	sclp_vt220_tty = NULL;
+	sclp_vt220_flush_later = 0;
+
+	/* Allocate pages for output buffering */
+	for (i = 0; i < (early ? MAX_CONSOLE_PAGES : MAX_KMEM_PAGES); i++) {
+		if (early)
+			page = alloc_bootmem_low_pages(PAGE_SIZE);
+		else
+			page = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
+		if (!page)
+			return -ENOMEM;
+		list_add_tail((struct list_head *) page, &sclp_vt220_empty);
+	}
+	return 0;
+}
+
+static struct tty_operations sclp_vt220_ops = {
+	.open = sclp_vt220_open,
+	.close = sclp_vt220_close,
+	.write = sclp_vt220_write,
+	.put_char = sclp_vt220_put_char,
+	.flush_chars = sclp_vt220_flush_chars,
+	.write_room = sclp_vt220_write_room,
+	.chars_in_buffer = sclp_vt220_chars_in_buffer,
+	.flush_buffer = sclp_vt220_flush_buffer
+};
+
+/*
+ * Register driver with SCLP and Linux and initialize internal tty structures.
+ */
+int __init
+sclp_vt220_tty_init(void)
+{
+	struct tty_driver *driver;
+	int rc;
+
+	/* Note: we're not testing for CONSOLE_IS_SCLP here to preserve
+	 * symmetry between VM and LPAR systems regarding ttyS1. */
+	driver = alloc_tty_driver(1);
+	if (!driver)
+		return -ENOMEM;
+	rc = __sclp_vt220_init(0);
+	if (rc) {
+		put_tty_driver(driver);
+		return rc;
+	}
+	rc = sclp_register(&sclp_vt220_register);
+	if (rc) {
+		printk(KERN_ERR SCLP_VT220_PRINT_HEADER
+		       "could not register tty - "
+		       "sclp_register returned %d\n", rc);
+		put_tty_driver(driver);
+		return rc;
+	}
+
+	driver->owner = THIS_MODULE;
+	driver->driver_name = SCLP_VT220_DRIVER_NAME;
+	driver->name = SCLP_VT220_DEVICE_NAME;
+	driver->major = SCLP_VT220_MAJOR;
+	driver->minor_start = SCLP_VT220_MINOR;
+	driver->type = TTY_DRIVER_TYPE_SYSTEM;
+	driver->subtype = SYSTEM_TYPE_TTY;
+	driver->init_termios = tty_std_termios;
+	driver->flags = TTY_DRIVER_REAL_RAW;
+	tty_set_operations(driver, &sclp_vt220_ops);
+
+	rc = tty_register_driver(driver);
+	if (rc) {
+		printk(KERN_ERR SCLP_VT220_PRINT_HEADER
+		       "could not register tty - "
+		       "tty_register_driver returned %d\n", rc);
+		put_tty_driver(driver);
+		return rc;
+	}
+	sclp_vt220_driver = driver;
+	return 0;
+}
+
+module_init(sclp_vt220_tty_init);
+
+#ifdef CONFIG_SCLP_VT220_CONSOLE
+
+static void
+sclp_vt220_con_write(struct console *con, const char *buf, unsigned int count)
+{
+	__sclp_vt220_write(0, (const unsigned char *) buf, count, 1, 1);
+}
+
+static struct tty_driver *
+sclp_vt220_con_device(struct console *c, int *index)
+{
+	*index = 0;
+	return sclp_vt220_driver;
+}
+
+/*
+ * This routine is called from panic when the kernel is going to give up.
+ * We have to make sure that all buffers will be flushed to the SCLP.
+ * Note that this function may be called from within an interrupt context.
+ */
+static void
+sclp_vt220_con_unblank(void)
+{
+	__sclp_vt220_flush_buffer();
+}
+
+/* Structure needed to register with printk */
+static struct console sclp_vt220_console =
+{
+	.name = SCLP_VT220_CONSOLE_NAME,
+	.write = sclp_vt220_con_write,
+	.device = sclp_vt220_con_device,
+	.unblank = sclp_vt220_con_unblank,
+	.flags = CON_PRINTBUFFER,
+	.index = SCLP_VT220_CONSOLE_INDEX
+};
+
+static int __init
+sclp_vt220_con_init(void)
+{
+	int rc;
+
+	if (!CONSOLE_IS_SCLP)
+		return 0;
+	rc = __sclp_vt220_init(1);
+	if (rc)
+		return rc;
+	/* Attach linux console */
+	register_console(&sclp_vt220_console);
+	return 0;
+}
+
+console_initcall(sclp_vt220_con_init);
+#endif /* CONFIG_SCLP_VT220_CONSOLE */
+