// SPDX-License-Identifier: GPL-2.0
/*
 * IBM/3270 Driver - fullscreen driver.
 *
 * Author(s):
 *   Original 3270 Code for 2.4 written by Richard Hitt (UTS Global)
 *   Rewritten for 2.5/2.6 by Martin Schwidefsky <schwidefsky@de.ibm.com>
 *     Copyright IBM Corp. 2003, 2009
 */

#include <linux/memblock.h>
#include <linux/console.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/compat.h>
#include <linux/sched/signal.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/types.h>

#include <asm/ccwdev.h>
#include <asm/cio.h>
#include <asm/ebcdic.h>
#include <asm/idals.h>

#include "raw3270.h"
#include "ctrlchar.h"

static struct raw3270_fn fs3270_fn;

struct fs3270 {
        struct raw3270_view view;
        struct pid *fs_pid;             /* Pid of controlling program. */
        int read_command;               /* ccw command to use for reads. */
        int write_command;              /* ccw command to use for writes. */
        int attention;                  /* Got attention. */
        int active;                     /* Fullscreen view is active. */
        struct raw3270_request *init;   /* single init request. */
        wait_queue_head_t wait;         /* Init & attention wait queue. */
        struct idal_buffer *rdbuf;      /* full-screen-deactivate buffer */
        size_t rdbuf_size;              /* size of data returned by RDBUF */
};

static DEFINE_MUTEX(fs3270_mutex);

static void
fs3270_wake_up(struct raw3270_request *rq, void *data)
{
        wake_up((wait_queue_head_t *) data);
}

static inline int
fs3270_working(struct fs3270 *fp)
{
        /*
         * The fullscreen view is in working order if the view
         * has been activated AND the initial request is finished.
         */
        return fp->active && raw3270_request_final(fp->init);
}

static int
fs3270_do_io(struct raw3270_view *view, struct raw3270_request *rq)
{
        struct fs3270 *fp;
        int rc;

        fp = (struct fs3270 *) view;
        rq->callback = fs3270_wake_up;
        rq->callback_data = &fp->wait;

        do {
                if (!fs3270_working(fp)) {
                        /* Fullscreen view isn't ready yet. */
                        rc = wait_event_interruptible(fp->wait,
                                                      fs3270_working(fp));
                        if (rc != 0)
                                break;
                }
                rc = raw3270_start(view, rq);
                if (rc == 0) {
                        /* Started successfully. Now wait for completion. */
                        wait_event(fp->wait, raw3270_request_final(rq));
                }
        } while (rc == -EACCES);
        return rc;
}

/*
 * Switch to the fullscreen view.
 */
static void
fs3270_reset_callback(struct raw3270_request *rq, void *data)
{
        struct fs3270 *fp;

        fp = (struct fs3270 *) rq->view;
        raw3270_request_reset(rq);
        wake_up(&fp->wait);
}

static void
fs3270_restore_callback(struct raw3270_request *rq, void *data)
{
        struct fs3270 *fp;

        fp = (struct fs3270 *) rq->view;
        if (rq->rc != 0 || rq->rescnt != 0) {
                if (fp->fs_pid)
                        kill_pid(fp->fs_pid, SIGHUP, 1);
        }
        fp->rdbuf_size = 0;
        raw3270_request_reset(rq);
        wake_up(&fp->wait);
}

static int
fs3270_activate(struct raw3270_view *view)
{
        struct fs3270 *fp;
        char *cp;
        int rc;

        fp = (struct fs3270 *) view;

        /* If an old init command is still running just return. */
        if (!raw3270_request_final(fp->init))
                return 0;

        if (fp->rdbuf_size == 0) {
                /* No saved buffer. Just clear the screen. */
                raw3270_request_set_cmd(fp->init, TC_EWRITEA);
                fp->init->callback = fs3270_reset_callback;
        } else {
                /* Restore fullscreen buffer saved by fs3270_deactivate. */
                raw3270_request_set_cmd(fp->init, TC_EWRITEA);
                raw3270_request_set_idal(fp->init, fp->rdbuf);
                fp->init->ccw.count = fp->rdbuf_size;
                cp = fp->rdbuf->data[0];
                cp[0] = TW_KR;
                cp[1] = TO_SBA;
                cp[2] = cp[6];
                cp[3] = cp[7];
                cp[4] = TO_IC;
                cp[5] = TO_SBA;
                cp[6] = 0x40;
                cp[7] = 0x40;
                fp->init->rescnt = 0;
                fp->init->callback = fs3270_restore_callback;
        }
        rc = fp->init->rc = raw3270_start_locked(view, fp->init);
        if (rc)
                fp->init->callback(fp->init, NULL);
        else
                fp->active = 1;
        return rc;
}

/*
 * Shutdown fullscreen view.
 */
static void
fs3270_save_callback(struct raw3270_request *rq, void *data)
{
        struct fs3270 *fp;

        fp = (struct fs3270 *) rq->view;

        /* Correct idal buffer element 0 address. */
        fp->rdbuf->data[0] -= 5;
        fp->rdbuf->size += 5;

        /*
         * If the rdbuf command failed or the idal buffer is
         * to small for the amount of data returned by the
         * rdbuf command, then we have no choice but to send
         * a SIGHUP to the application.
         */
        if (rq->rc != 0 || rq->rescnt == 0) {
                if (fp->fs_pid)
                        kill_pid(fp->fs_pid, SIGHUP, 1);
                fp->rdbuf_size = 0;
        } else
                fp->rdbuf_size = fp->rdbuf->size - rq->rescnt;
        raw3270_request_reset(rq);
        wake_up(&fp->wait);
}

static void
fs3270_deactivate(struct raw3270_view *view)
{
        struct fs3270 *fp;

        fp = (struct fs3270 *) view;
        fp->active = 0;

        /* If an old init command is still running just return. */
        if (!raw3270_request_final(fp->init))
                return;

        /* Prepare read-buffer request. */
        raw3270_request_set_cmd(fp->init, TC_RDBUF);
        /*
         * Hackish: skip first 5 bytes of the idal buffer to make
         * room for the TW_KR/TO_SBA/<address>/<address>/TO_IC sequence
         * in the activation command.
         */
        fp->rdbuf->data[0] += 5;
        fp->rdbuf->size -= 5;
        raw3270_request_set_idal(fp->init, fp->rdbuf);
        fp->init->rescnt = 0;
        fp->init->callback = fs3270_save_callback;

        /* Start I/O to read in the 3270 buffer. */
        fp->init->rc = raw3270_start_locked(view, fp->init);
        if (fp->init->rc)
                fp->init->callback(fp->init, NULL);
}

static void
fs3270_irq(struct fs3270 *fp, struct raw3270_request *rq, struct irb *irb)
{
        /* Handle ATTN. Set indication and wake waiters for attention. */
        if (irb->scsw.cmd.dstat & DEV_STAT_ATTENTION) {
                fp->attention = 1;
                wake_up(&fp->wait);
        }

        if (rq) {
                if (irb->scsw.cmd.dstat & DEV_STAT_UNIT_CHECK)
                        rq->rc = -EIO;
                else
                        /* Normal end. Copy residual count. */
                        rq->rescnt = irb->scsw.cmd.count;
        }
}

/*
 * Process reads from fullscreen 3270.
 */
static ssize_t
fs3270_read(struct file *filp, char __user *data, size_t count, loff_t *off)
{
        struct fs3270 *fp;
        struct raw3270_request *rq;
        struct idal_buffer *ib;
        ssize_t rc;
        
        if (count == 0 || count > 65535)
                return -EINVAL;
        fp = filp->private_data;
        if (!fp)
                return -ENODEV;
        ib = idal_buffer_alloc(count, 0);
        if (IS_ERR(ib))
                return -ENOMEM;
        rq = raw3270_request_alloc(0);
        if (!IS_ERR(rq)) {
                if (fp->read_command == 0 && fp->write_command != 0)
                        fp->read_command = 6;
                raw3270_request_set_cmd(rq, fp->read_command ? : 2);
                raw3270_request_set_idal(rq, ib);
                rc = wait_event_interruptible(fp->wait, fp->attention);
                fp->attention = 0;
                if (rc == 0) {
                        rc = fs3270_do_io(&fp->view, rq);
                        if (rc == 0) {
                                count -= rq->rescnt;
                                if (idal_buffer_to_user(ib, data, count) != 0)
                                        rc = -EFAULT;
                                else
                                        rc = count;

                        }
                }
                raw3270_request_free(rq);
        } else
                rc = PTR_ERR(rq);
        idal_buffer_free(ib);
        return rc;
}

/*
 * Process writes to fullscreen 3270.
 */
static ssize_t
fs3270_write(struct file *filp, const char __user *data, size_t count, loff_t *off)
{
        struct fs3270 *fp;
        struct raw3270_request *rq;
        struct idal_buffer *ib;
        int write_command;
        ssize_t rc;

        fp = filp->private_data;
        if (!fp)
                return -ENODEV;
        ib = idal_buffer_alloc(count, 0);
        if (IS_ERR(ib))
                return -ENOMEM;
        rq = raw3270_request_alloc(0);
        if (!IS_ERR(rq)) {
                if (idal_buffer_from_user(ib, data, count) == 0) {
                        write_command = fp->write_command ? : 1;
                        if (write_command == 5)
                                write_command = 13;
                        raw3270_request_set_cmd(rq, write_command);
                        raw3270_request_set_idal(rq, ib);
                        rc = fs3270_do_io(&fp->view, rq);
                        if (rc == 0)
                                rc = count - rq->rescnt;
                } else
                        rc = -EFAULT;
                raw3270_request_free(rq);
        } else
                rc = PTR_ERR(rq);
        idal_buffer_free(ib);
        return rc;
}

/*
 * process ioctl commands for the tube driver
 */
static long
fs3270_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
        char __user *argp;
        struct fs3270 *fp;
        struct raw3270_iocb iocb;
        int rc;

        fp = filp->private_data;
        if (!fp)
                return -ENODEV;
        if (is_compat_task())
                argp = compat_ptr(arg);
        else
                argp = (char __user *)arg;
        rc = 0;
        mutex_lock(&fs3270_mutex);
        switch (cmd) {
        case TUBICMD:
                fp->read_command = arg;
                break;
        case TUBOCMD:
                fp->write_command = arg;
                break;
        case TUBGETI:
                rc = put_user(fp->read_command, argp);
                break;
        case TUBGETO:
                rc = put_user(fp->write_command, argp);
                break;
        case TUBGETMOD:
                iocb.model = fp->view.model;
                iocb.line_cnt = fp->view.rows;
                iocb.col_cnt = fp->view.cols;
                iocb.pf_cnt = 24;
                iocb.re_cnt = 20;
                iocb.map = 0;
                if (copy_to_user(argp, &iocb, sizeof(struct raw3270_iocb)))
                        rc = -EFAULT;
                break;
        }
        mutex_unlock(&fs3270_mutex);
        return rc;
}

/*
 * Allocate fs3270 structure.
 */
static struct fs3270 *
fs3270_alloc_view(void)
{
        struct fs3270 *fp;

        fp = kzalloc(sizeof(struct fs3270),GFP_KERNEL);
        if (!fp)
                return ERR_PTR(-ENOMEM);
        fp->init = raw3270_request_alloc(0);
        if (IS_ERR(fp->init)) {
                kfree(fp);
                return ERR_PTR(-ENOMEM);
        }
        return fp;
}

/*
 * Free fs3270 structure.
 */
static void
fs3270_free_view(struct raw3270_view *view)
{
        struct fs3270 *fp;

        fp = (struct fs3270 *) view;
        if (fp->rdbuf)
                idal_buffer_free(fp->rdbuf);
        raw3270_request_free(((struct fs3270 *) view)->init);
        kfree(view);
}

/*
 * Unlink fs3270 data structure from filp.
 */
static void
fs3270_release(struct raw3270_view *view)
{
        struct fs3270 *fp;

        fp = (struct fs3270 *) view;
        if (fp->fs_pid)
                kill_pid(fp->fs_pid, SIGHUP, 1);
}

/* View to a 3270 device. Can be console, tty or fullscreen. */
static struct raw3270_fn fs3270_fn = {
        .activate = fs3270_activate,
        .deactivate = fs3270_deactivate,
        .intv = (void *) fs3270_irq,
        .release = fs3270_release,
        .free = fs3270_free_view
};

/*
 * This routine is called whenever a 3270 fullscreen device is opened.
 */
static int
fs3270_open(struct inode *inode, struct file *filp)
{
        struct fs3270 *fp;
        struct idal_buffer *ib;
        int minor, rc = 0;

        if (imajor(file_inode(filp)) != IBM_FS3270_MAJOR)
                return -ENODEV;
        minor = iminor(file_inode(filp));
        /* Check for minor 0 multiplexer. */
        if (minor == 0) {
                struct tty_struct *tty = get_current_tty();
                if (!tty || tty->driver->major != IBM_TTY3270_MAJOR) {
                        tty_kref_put(tty);
                        return -ENODEV;
                }
                minor = tty->index;
                tty_kref_put(tty);
        }
        mutex_lock(&fs3270_mutex);
        /* Check if some other program is already using fullscreen mode. */
        fp = (struct fs3270 *) raw3270_find_view(&fs3270_fn, minor);
        if (!IS_ERR(fp)) {
                raw3270_put_view(&fp->view);
                rc = -EBUSY;
                goto out;
        }
        /* Allocate fullscreen view structure. */
        fp = fs3270_alloc_view();
        if (IS_ERR(fp)) {
                rc = PTR_ERR(fp);
                goto out;
        }

        init_waitqueue_head(&fp->wait);
        fp->fs_pid = get_pid(task_pid(current));
        rc = raw3270_add_view(&fp->view, &fs3270_fn, minor,
                              RAW3270_VIEW_LOCK_BH);
        if (rc) {
                fs3270_free_view(&fp->view);
                goto out;
        }

        /* Allocate idal-buffer. */
        ib = idal_buffer_alloc(2*fp->view.rows*fp->view.cols + 5, 0);
        if (IS_ERR(ib)) {
                raw3270_put_view(&fp->view);
                raw3270_del_view(&fp->view);
                rc = PTR_ERR(ib);
                goto out;
        }
        fp->rdbuf = ib;

        rc = raw3270_activate_view(&fp->view);
        if (rc) {
                raw3270_put_view(&fp->view);
                raw3270_del_view(&fp->view);
                goto out;
        }
        stream_open(inode, filp);
        filp->private_data = fp;
out:
        mutex_unlock(&fs3270_mutex);
        return rc;
}

/*
 * This routine is called when the 3270 tty is closed. We wait
 * for the remaining request to be completed. Then we clean up.
 */
static int
fs3270_close(struct inode *inode, struct file *filp)
{
        struct fs3270 *fp;

        fp = filp->private_data;
        filp->private_data = NULL;
        if (fp) {
                put_pid(fp->fs_pid);
                fp->fs_pid = NULL;
                raw3270_reset(&fp->view);
                raw3270_put_view(&fp->view);
                raw3270_del_view(&fp->view);
        }
        return 0;
}

static const struct file_operations fs3270_fops = {
        .owner           = THIS_MODULE,         /* owner */
        .read            = fs3270_read,         /* read */
        .write           = fs3270_write,        /* write */
        .unlocked_ioctl  = fs3270_ioctl,        /* ioctl */
        .compat_ioctl    = fs3270_ioctl,        /* ioctl */
        .open            = fs3270_open,         /* open */
        .release         = fs3270_close,        /* release */
        .llseek         = no_llseek,
};

static void fs3270_create_cb(int minor)
{
        __register_chrdev(IBM_FS3270_MAJOR, minor, 1, "tub", &fs3270_fops);
        device_create(class3270, NULL, MKDEV(IBM_FS3270_MAJOR, minor),
                      NULL, "3270/tub%d", minor);
}

static void fs3270_destroy_cb(int minor)
{
        device_destroy(class3270, MKDEV(IBM_FS3270_MAJOR, minor));
        __unregister_chrdev(IBM_FS3270_MAJOR, minor, 1, "tub");
}

static struct raw3270_notifier fs3270_notifier =
{
        .create = fs3270_create_cb,
        .destroy = fs3270_destroy_cb,
};

/*
 * 3270 fullscreen driver initialization.
 */
static int __init
fs3270_init(void)
{
        int rc;

        rc = __register_chrdev(IBM_FS3270_MAJOR, 0, 1, "fs3270", &fs3270_fops);
        if (rc)
                return rc;
        device_create(class3270, NULL, MKDEV(IBM_FS3270_MAJOR, 0),
                      NULL, "3270/tub");
        raw3270_register_notifier(&fs3270_notifier);
        return 0;
}

static void __exit
fs3270_exit(void)
{
        raw3270_unregister_notifier(&fs3270_notifier);
        device_destroy(class3270, MKDEV(IBM_FS3270_MAJOR, 0));
        __unregister_chrdev(IBM_FS3270_MAJOR, 0, 1, "fs3270");
}

MODULE_LICENSE("GPL");
MODULE_ALIAS_CHARDEV_MAJOR(IBM_FS3270_MAJOR);

module_init(fs3270_init);
module_exit(fs3270_exit);