sclp_vt220.c

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/*
 * SCLP VT220 terminal driver.
 *
 * Copyright IBM Corp. 2003, 2009
 *
 * Author(s): Peter Oberparleiter <[email protected]>
 */

#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/interrupt.h>
#include <linux/init.h>
#include <linux/reboot.h>
#include <linux/slab.h>

#include <asm/uaccess.h>
#include "sclp.h"

#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 */

/* 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;

static struct tty_port sclp_vt220_port;

/* 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;

/* Suspend mode flag */
static int sclp_vt220_suspended;

/* Flag that output queue is currently running */
static int sclp_vt220_queue_running;

/* 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;

/* Counter controlling core driver initialization. */
static int __initdata sclp_vt220_init_count;

/* 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_pm_event_fn(struct sclp_register *reg,
                   enum sclp_pm_event sclp_pm_event);
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,
    .pm_event_fn        = sclp_vt220_pm_event_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)
{
    struct tty_struct *tty;
    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);
        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);
        if (!request || sclp_vt220_suspended) {
            sclp_vt220_queue_running = 0;
            spin_unlock_irqrestore(&sclp_vt220_lock, flags);
            break;
        }
        spin_unlock_irqrestore(&sclp_vt220_lock, flags);
    } while (__sclp_vt220_emit(request));
    if (request == NULL && sclp_vt220_flush_later)
        sclp_vt220_emit_current();
    /* Check if the tty needs a wake up call */
    tty = tty_port_tty_get(&sclp_vt220_port);
    if (tty) {
        tty_wakeup(tty);
        tty_kref_put(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 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);
    if (sclp_vt220_current_request) {
        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)) {
            list_add_tail(&sclp_vt220_current_request->list,
                      &sclp_vt220_outqueue);
            sclp_vt220_current_request = NULL;
            if (timer_pending(&sclp_vt220_timer))
                del_timer(&sclp_vt220_timer);
        }
        sclp_vt220_flush_later = 0;
    }
    if (sclp_vt220_queue_running || sclp_vt220_suspended)
        goto out_unlock;
    if (list_empty(&sclp_vt220_outqueue))
        goto out_unlock;
    request = list_first_entry(&sclp_vt220_outqueue,
                   struct sclp_vt220_request, list);
    sclp_vt220_queue_running = 1;
    spin_unlock_irqrestore(&sclp_vt220_lock, flags);

    if (__sclp_vt220_emit(request))
        sclp_vt220_process_queue(request);
    return;
out_unlock:
    spin_unlock_irqrestore(&sclp_vt220_lock, flags);
}

#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, int may_fail)
{
    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 an 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 (may_fail || sclp_vt220_suspended)
                    goto out;
                else
                    sclp_sync_wait();
                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);
out:
    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, 1);
}

#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)
{
    struct tty_struct *tty = tty_port_tty_get(&sclp_vt220_port);
    char *buffer;
    unsigned int count;

    /* Ignore input if device is not open */
    if (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(tty, buffer, count);
        tty_flip_buffer_push(tty);
        break;
    }
    tty_kref_put(tty);
}

/*
 * 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) {
        tty_port_tty_set(&sclp_vt220_port, tty);
        tty->low_latency = 0;
        if (!tty->winsize.ws_row && !tty->winsize.ws_col) {
            tty->winsize.ws_row = 24;
            tty->winsize.ws_col = 80;
        }
    }
    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)
        tty_port_tty_set(&sclp_vt220_port, 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.
 */
static int
sclp_vt220_put_char(struct tty_struct *tty, unsigned char ch)
{
    return __sclp_vt220_write(&ch, 1, 0, 0, 1);
}

/*
 * 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_queue_running)
        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;
}

/*
 * 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();
}

/* Release allocated pages. */
static void __init __sclp_vt220_free_pages(void)
{
    struct list_head *page, *p;

    list_for_each_safe(page, p, &sclp_vt220_empty) {
        list_del(page);
        free_page((unsigned long) page);
    }
}

/* Release memory and unregister from sclp core. Controlled by init counting -
 * only the last invoker will actually perform these actions. */
static void __init __sclp_vt220_cleanup(void)
{
    sclp_vt220_init_count--;
    if (sclp_vt220_init_count != 0)
        return;
    sclp_unregister(&sclp_vt220_register);
    __sclp_vt220_free_pages();
}

/* Allocate buffer pages and register with sclp core. Controlled by init
 * counting - only the first invoker will actually perform these actions. */
static int __init __sclp_vt220_init(int num_pages)
{
    void *page;
    int i;
    int rc;

    sclp_vt220_init_count++;
    if (sclp_vt220_init_count != 1)
        return 0;
    spin_lock_init(&sclp_vt220_lock);
    INIT_LIST_HEAD(&sclp_vt220_empty);
    INIT_LIST_HEAD(&sclp_vt220_outqueue);
    init_timer(&sclp_vt220_timer);
    tty_port_init(&sclp_vt220_port);
    sclp_vt220_current_request = NULL;
    sclp_vt220_buffered_chars = 0;
    sclp_vt220_flush_later = 0;

    /* Allocate pages for output buffering */
    rc = -ENOMEM;
    for (i = 0; i < num_pages; i++) {
        page = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
        if (!page)
            goto out;
        list_add_tail(page, &sclp_vt220_empty);
    }
    rc = sclp_register(&sclp_vt220_register);
out:
    if (rc) {
        __sclp_vt220_free_pages();
        sclp_vt220_init_count--;
    }
    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;

    /* 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(MAX_KMEM_PAGES);
    if (rc)
        goto out_driver;

    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);
    tty_port_link_device(&sclp_vt220_port, driver, 0);

    rc = tty_register_driver(driver);
    if (rc)
        goto out_init;
    sclp_vt220_driver = driver;
    return 0;

out_init:
    __sclp_vt220_cleanup();
out_driver:
    put_tty_driver(driver);
    return rc;
}
__initcall(sclp_vt220_tty_init);

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_queue_running) {
        spin_unlock_irqrestore(&sclp_vt220_lock, flags);
        sclp_sync_wait();
        spin_lock_irqsave(&sclp_vt220_lock, flags);
    }
    spin_unlock_irqrestore(&sclp_vt220_lock, flags);
}

/*
 * Resume console: If there are cached messages, emit them.
 */
static void sclp_vt220_resume(void)
{
    unsigned long flags;

    spin_lock_irqsave(&sclp_vt220_lock, flags);
    sclp_vt220_suspended = 0;
    spin_unlock_irqrestore(&sclp_vt220_lock, flags);
    sclp_vt220_emit_current();
}

/*
 * Suspend console: Set suspend flag and flush console
 */
static void sclp_vt220_suspend(void)
{
    unsigned long flags;

    spin_lock_irqsave(&sclp_vt220_lock, flags);
    sclp_vt220_suspended = 1;
    spin_unlock_irqrestore(&sclp_vt220_lock, flags);
    __sclp_vt220_flush_buffer();
}

static void sclp_vt220_pm_event_fn(struct sclp_register *reg,
                   enum sclp_pm_event sclp_pm_event)
{
    switch (sclp_pm_event) {
    case SCLP_PM_EVENT_FREEZE:
        sclp_vt220_suspend();
        break;
    case SCLP_PM_EVENT_RESTORE:
    case SCLP_PM_EVENT_THAW:
        sclp_vt220_resume();
        break;
    }
}

#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, 0);
}

static struct tty_driver *
sclp_vt220_con_device(struct console *c, int *index)
{
    *index = 0;
    return sclp_vt220_driver;
}

static int
sclp_vt220_notify(struct notifier_block *self,
              unsigned long event, void *data)
{
    __sclp_vt220_flush_buffer();
    return NOTIFY_OK;
}

static struct notifier_block on_panic_nb = {
    .notifier_call = sclp_vt220_notify,
    .priority = 1,
};

static struct notifier_block on_reboot_nb = {
    .notifier_call = sclp_vt220_notify,
    .priority = 1,
};

/* 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,
    .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(MAX_CONSOLE_PAGES);
    if (rc)
        return rc;
    /* Attach linux console */
    atomic_notifier_chain_register(&panic_notifier_list, &on_panic_nb);
    register_reboot_notifier(&on_reboot_nb);
    register_console(&sclp_vt220_console);
    return 0;
}

console_initcall(sclp_vt220_con_init);
#endif /* CONFIG_SCLP_VT220_CONSOLE */