sclp_vt220.c

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/*
 *  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 <[e-mail]>
 */

#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		"ttysclp"
#define SCLP_VT220_CONSOLE_NAME		"ttyS"
#define SCLP_VT220_CONSOLE_INDEX	1	/* console=ttyS1 */
#define SCLP_VT220_BUF_SIZE		80

/* 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.
 */
static int
sclp_vt220_add_msg(struct sclp_vt220_request *request,
		   const unsigned char *msg, int count, 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 */
			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 {
		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
 * 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(const unsigned char *buf, int count, int do_schedule,
		   int convertlf)
{
	unsigned long flags;
	void *page;
	int written;
	int overall_written;