Committer: Michael Beasley <mike@snafu.setup>

[mikesnafu-overlay.git] / drivers / s390 / char / sclp_vt220.c

/*
 *  drivers/s390/char/sclp_vt220.c
 *    SCLP VT220 terminal driver.
 *
 *  S390 version
 *    Copyright IBM Corp. 2003,2008
 *    Author(s): Peter Oberparleiter <Peter.Oberparleiter@de.ibm.com>
 */

#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/tty_flip.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;
};

/* 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 int __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;
        void *page;

        do {
                /* 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. */
                request = NULL;
                if (!list_empty(&sclp_vt220_outqueue))
                        request = list_entry(sclp_vt220_outqueue.next,
                                             struct sclp_vt220_request, list);
                spin_unlock_irqrestore(&sclp_vt220_lock, flags);
        } while (request && __sclp_vt220_emit(request));
        if (request == NULL && 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) {
                tty_wakeup(sclp_vt220_tty);
        }
}

#define SCLP_BUFFER_MAX_RETRY           1

/*
 * 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;
                        if (sclp_add_request(request) == 0)
                                return;
                }
                break;

        case 0x0040: /* SCLP equipment check */
                if (++vt220_request->retry_count > SCLP_BUFFER_MAX_RETRY)
                        break;
                sccb->header.response_code = 0x0000;
                vt220_request->sclp_req.status = SCLP_REQ_FILLED;
                if (sclp_add_request(request) == 0)
                        return;
                break;

        default:
                break;
        }
        sclp_vt220_process_queue(vt220_request);
}

/*
 * Emit vt220 request buffer to SCLP. Return zero on success, non-zero
 * otherwise.
 */
static int
__sclp_vt220_emit(struct sclp_vt220_request *request)
{
        if (!(sclp_vt220_register.sclp_receive_mask & EVTYP_VT220MSG_MASK)) {
                request->sclp_req.status = SCLP_REQ_FAILED;
                return -EIO;
        }
        request->sclp_req.command = SCLP_CMDW_WRITE_EVENT_DATA;
        request->sclp_req.status = SCLP_REQ_FILLED;
        request->sclp_req.callback = sclp_vt220_callback;
        request->sclp_req.callback_data = (void *) request;

        return 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))
                sclp_vt220_process_queue(request);
}

/*
 * Queue and emit current request. Return zero on success, non-zero otherwise.
 */
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;
        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/20

/* 
 * 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;

        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_atomic())
                                        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, convertlf);
                overall_written += written;
                if (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, const unsigned char *buf, int count)
{
        return __sclp_vt220_write(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--;
                tty_insert_flip_string(sclp_vt220_tty, buffer, 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)
{
        if (tty->count == 1) {
                sclp_vt220_tty = tty;
                tty->driver_data = kmalloc(SCLP_VT220_BUF_SIZE, GFP_KERNEL);
                if (tty->driver_data == NULL)
                        return -ENOMEM;
                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) {
                sclp_vt220_tty = NULL;
                kfree(tty->driver_data);
                tty->driver_data = 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(&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 void __init __sclp_vt220_cleanup(void)
{
        struct list_head *page, *p;

        list_for_each_safe(page, p, &sclp_vt220_empty) {
                list_del(page);
                if (slab_is_available())
                        free_page((unsigned long) page);
                else
                        free_bootmem((unsigned long) page, PAGE_SIZE);
        }
        if (!list_empty(&sclp_vt220_register.list))
                sclp_unregister(&sclp_vt220_register);
        sclp_vt220_initialized = 0;
}

static int __init __sclp_vt220_init(void)
{
        void *page;
        int i;
        int num_pages;
        int rc;

        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 */
        num_pages = slab_is_available() ? MAX_KMEM_PAGES : MAX_CONSOLE_PAGES;
        for (i = 0; i < num_pages; i++) {
                if (slab_is_available())
                        page = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
                else
                        page = alloc_bootmem_low_pages(PAGE_SIZE);
                if (!page) {
                        __sclp_vt220_cleanup();
                        return -ENOMEM;
                }
                list_add_tail((struct list_head *) page, &sclp_vt220_empty);
        }
        rc = sclp_register(&sclp_vt220_register);
        if (rc) {
                printk(KERN_ERR SCLP_VT220_PRINT_HEADER
                       "could not register vt220 - "
                       "sclp_register returned %d\n", rc);
                __sclp_vt220_cleanup();
        }
        return rc;
}

static const 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.
 */
static int __init sclp_vt220_tty_init(void)
{
        struct tty_driver *driver;
        int rc;
        int cleanup;

        /* 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;
        cleanup = !sclp_vt220_initialized;
        rc = __sclp_vt220_init();
        if (rc)
                goto out_driver;

        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);
                goto out_init;
        }
        sclp_vt220_driver = driver;
        return 0;

out_init:
        if (cleanup)
                __sclp_vt220_cleanup();
out_driver:
        put_tty_driver(driver);
        return rc;
}
__initcall(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((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();
        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 */