monreader.c

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		monpriv->read_index = (monpriv->read_index + 1) %
				      MON_MSGLIM;
		atomic_dec(&monpriv->read_ready);
		return ERR_PTR(-EOVERFLOW);
	}
	return monmsg;
}


/******************************************************************************
 *                               IUCV handler                                 *
 *****************************************************************************/
static void mon_iucv_path_complete(struct iucv_path *path, u8 ipuser[16])
{
	struct mon_private *monpriv = path->private;

	P_DEBUG("IUCV connection completed\n");
	P_DEBUG("IUCV ACCEPT (from *MONITOR): Version = 0x%02X, Event = "
		"0x%02X, Sample = 0x%02X\n",
		ipuser[0], ipuser[1], ipuser[2]);
	atomic_set(&monpriv->iucv_connected, 1);
	wake_up(&mon_conn_wait_queue);
}

static void mon_iucv_path_severed(struct iucv_path *path, u8 ipuser[16])
{
	struct mon_private *monpriv = path->private;

	P_ERROR("IUCV connection severed with rc = 0x%X\n", ipuser[0]);
	iucv_path_sever(path, NULL);
	atomic_set(&monpriv->iucv_severed, 1);
	wake_up(&mon_conn_wait_queue);
	wake_up_interruptible(&mon_read_wait_queue);
}

static void mon_iucv_message_pending(struct iucv_path *path,
				     struct iucv_message *msg)
{
	struct mon_private *monpriv = path->private;

	P_DEBUG("IUCV message pending\n");
	memcpy(&monpriv->msg_array[monpriv->write_index]->msg,
	       msg, sizeof(*msg));
	if (atomic_inc_return(&monpriv->msglim_count) == MON_MSGLIM) {
		P_WARNING("IUCV message pending, message limit (%i) reached\n",
			  MON_MSGLIM);
		monpriv->msg_array[monpriv->write_index]->msglim_reached = 1;
	}
	monpriv->write_index = (monpriv->write_index + 1) % MON_MSGLIM;
	atomic_inc(&monpriv->read_ready);
	wake_up_interruptible(&mon_read_wait_queue);
}

static struct iucv_handler monreader_iucv_handler = {
	.path_complete	 = mon_iucv_path_complete,
	.path_severed	 = mon_iucv_path_severed,
	.message_pending = mon_iucv_message_pending,
};

/******************************************************************************
 *                               file operations                              *
 *****************************************************************************/
static int mon_open(struct inode *inode, struct file *filp)
{
	struct mon_private *monpriv;
	int rc;

	/*
	 * only one user allowed
	 */
	rc = -EBUSY;
	if (test_and_set_bit(MON_IN_USE, &mon_in_use))
		goto out;

	rc = -ENOMEM;
	monpriv = mon_alloc_mem();
	if (!monpriv)
		goto out_use;

	/*
	 * Connect to *MONITOR service
	 */
	monpriv->path = iucv_path_alloc(MON_MSGLIM, IUCV_IPRMDATA, GFP_KERNEL);
	if (!monpriv->path)
		goto out_priv;
	rc = iucv_path_connect(monpriv->path, &monreader_iucv_handler,
			       MON_SERVICE, NULL, user_data_connect, monpriv);
	if (rc) {
		P_ERROR("iucv connection to *MONITOR failed with "
			"IPUSER SEVER code = %i\n", rc);
		rc = -EIO;
		goto out_path;
	}
	/*
	 * Wait for connection confirmation
	 */
	wait_event(mon_conn_wait_queue,
		   atomic_read(&monpriv->iucv_connected) ||
		   atomic_read(&monpriv->iucv_severed));
	if (atomic_read(&monpriv->iucv_severed)) {
		atomic_set(&monpriv->iucv_severed, 0);
		atomic_set(&monpriv->iucv_connected, 0);
		rc = -EIO;
		goto out_path;
	}
	P_INFO("open, established connection to *MONITOR service\n\n");
	filp->private_data = monpriv;
	return nonseekable_open(inode, filp);

out_path:
	kfree(monpriv->path);
out_priv:
	mon_free_mem(monpriv);
out_use:
	clear_bit(MON_IN_USE, &mon_in_use);
out:
	return rc;
}

static int mon_close(struct inode *inode, struct file *filp)
{
	int rc, i;
	struct mon_private *monpriv = filp->private_data;

	/*
	 * Close IUCV connection and unregister
	 */
	rc = iucv_path_sever(monpriv->path, user_data_sever);
	if (rc)
		P_ERROR("close, iucv_sever failed with rc = %i\n", rc);
	else
		P_INFO("close, terminated connection to *MONITOR service\n");

	atomic_set(&monpriv->iucv_severed, 0);
	atomic_set(&monpriv->iucv_connected, 0);
	atomic_set(&monpriv->read_ready, 0);
	atomic_set(&monpriv->msglim_count, 0);
	monpriv->write_index  = 0;
	monpriv->read_index   = 0;

	for (i = 0; i < MON_MSGLIM; i++)
		kfree(monpriv->msg_array[i]);
	kfree(monpriv);
	clear_bit(MON_IN_USE, &mon_in_use);
	return 0;
}

static ssize_t mon_read(struct file *filp, char __user *data,
			size_t count, loff_t *ppos)
{
	struct mon_private *monpriv = filp->private_data;
	struct mon_msg *monmsg;
	int ret;
	u32 mce_start;

	monmsg = mon_next_message(monpriv);
	if (IS_ERR(monmsg))
		return PTR_ERR(monmsg);

	if (!monmsg) {
		if (filp->f_flags & O_NONBLOCK)
			return -EAGAIN;
		ret = wait_event_interruptible(mon_read_wait_queue,
					atomic_read(&monpriv->read_ready) ||
					atomic_read(&monpriv->iucv_severed));
		if (ret)
			return ret;
		if (unlikely(atomic_read(&monpriv->iucv_severed)))
			return -EIO;
		monmsg = monpriv->msg_array[monpriv->read_index];
	}

	if (!monmsg->pos) {
		monmsg->pos = mon_mca_start(monmsg) + monmsg->mca_offset;
		mon_read_debug(monmsg, monpriv);
	}
	if (mon_check_mca(monmsg))
		goto reply;

	/* read monitor control element (12 bytes) first */
	mce_start = mon_mca_start(monmsg) + monmsg->mca_offset;
	if ((monmsg->pos >= mce_start) && (monmsg->pos < mce_start + 12)) {
		count = min(count, (size_t) mce_start + 12 - monmsg->pos);
		ret = copy_to_user(data, (void *) (unsigned long) monmsg->pos,
				   count);
		if (ret)
			return -EFAULT;
		monmsg->pos += count;
		if (monmsg->pos == mce_start + 12)
			monmsg->pos = mon_rec_start(monmsg);
		goto out_copy;
	}

	/* read records */
	if (monmsg->pos <= mon_rec_end(monmsg)) {
		count = min(count, (size_t) mon_rec_end(monmsg) - monmsg->pos
					    + 1);
		ret = copy_to_user(data, (void *) (unsigned long) monmsg->pos,
				   count);
		if (ret)
			return -EFAULT;
		monmsg->pos += count;
		if (monmsg->pos > mon_rec_end(monmsg))
			mon_next_mca(monmsg);
		goto out_copy;
	}
reply:
	ret = mon_send_reply(monmsg, monpriv);
	return ret;

out_copy:
	*ppos += count;
	return count;
}

static unsigned int mon_poll(struct file *filp, struct poll_table_struct *p)
{
	struct mon_private *monpriv = filp->private_data;

	poll_wait(filp, &mon_read_wait_queue, p);
	if (unlikely(atomic_read(&monpriv->iucv_severed)))
		return POLLERR;
	if (atomic_read(&monpriv->read_ready))
		return POLLIN | POLLRDNORM;
	return 0;
}

static const struct file_operations mon_fops = {
	.owner   = THIS_MODULE,
	.open    = &mon_open,
	.release = &mon_close,
	.read    = &mon_read,
	.poll    = &mon_poll,
};

static struct miscdevice mon_dev = {
	.name       = "monreader",
	.fops       = &mon_fops,
	.minor      = MISC_DYNAMIC_MINOR,
};

/******************************************************************************
 *                              module init/exit                              *
 *****************************************************************************/
static int __init mon_init(void)
{
	int rc;

	if (!MACHINE_IS_VM) {
		P_ERROR("not running under z/VM, driver not loaded\n");
		return -ENODEV;
	}

	/*
	 * Register with IUCV and connect to *MONITOR service
	 */
	rc = iucv_register(&monreader_iucv_handler, 1);
	if (rc) {
		P_ERROR("failed to register with iucv driver\n");
		return rc;
	}
	P_INFO("open, registered with IUCV\n");

	rc = segment_type(mon_dcss_name);
	if (rc < 0) {
		mon_segment_warn(rc, mon_dcss_name);
		goto out_iucv;
	}
	if (rc != SEG_TYPE_SC) {
		P_ERROR("segment %s has unsupported type, should be SC\n",
			mon_dcss_name);
		rc = -EINVAL;
		goto out_iucv;
	}

	rc = segment_load(mon_dcss_name, SEGMENT_SHARED,
			  &mon_dcss_start, &mon_dcss_end);
	if (rc < 0) {
		mon_segment_warn(rc, mon_dcss_name);
		rc = -EINVAL;
		goto out_iucv;
	}
	dcss_mkname(mon_dcss_name, &user_data_connect[8]);

	rc = misc_register(&mon_dev);
	if (rc < 0 ) {
		P_ERROR("misc_register failed, rc = %i\n", rc);
		goto out;
	}
	P_INFO("Loaded segment %s from %p to %p, size = %lu Byte\n",
		mon_dcss_name, (void *) mon_dcss_start, (void *) mon_dcss_end,
		mon_dcss_end - mon_dcss_start + 1);
	return 0;

out:
	segment_unload(mon_dcss_name);
out_iucv:
	iucv_unregister(&monreader_iucv_handler, 1);
	return rc;
}

static void __exit mon_exit(void)
{
	segment_unload(mon_dcss_name);
	WARN_ON(misc_deregister(&mon_dev) != 0);
	iucv_unregister(&monreader_iucv_handler, 1);
	return;
}


module_init(mon_init);
module_exit(mon_exit);

module_param_string(mondcss, mon_dcss_name, 9, 0444);
MODULE_PARM_DESC(mondcss, "Name of DCSS segment to be used for *MONITOR "
		 "service, max. 8 chars. Default is MONDCSS");

MODULE_AUTHOR("Gerald Schaefer <[e-mail]>");
MODULE_DESCRIPTION("Character device driver for reading z/VM "
		   "monitor service records.");
MODULE_LICENSE("GPL");