1// SPDX-License-Identifier: GPL-2.0+
   2/*
   3 * IBM eServer Hypervisor Virtual Console Server Device Driver
   4 * Copyright (C) 2003, 2004 IBM Corp.
   5 *  Ryan S. Arnold (rsa@us.ibm.com)
   6 *
   7 * Author(s) :  Ryan S. Arnold <rsa@us.ibm.com>
   8 *
   9 * This is the device driver for the IBM Hypervisor Virtual Console Server,
  10 * "hvcs".  The IBM hvcs provides a tty driver interface to allow Linux
  11 * user space applications access to the system consoles of logically
  12 * partitioned operating systems, e.g. Linux, running on the same partitioned
  13 * Power5 ppc64 system.  Physical hardware consoles per partition are not
  14 * practical on this hardware so system consoles are accessed by this driver
  15 * using inter-partition firmware interfaces to virtual terminal devices.
  16 *
  17 * A vty is known to the HMC as a "virtual serial server adapter".  It is a
  18 * virtual terminal device that is created by firmware upon partition creation
  19 * to act as a partitioned OS's console device.
  20 *
  21 * Firmware dynamically (via hotplug) exposes vty-servers to a running ppc64
  22 * Linux system upon their creation by the HMC or their exposure during boot.
  23 * The non-user interactive backend of this driver is implemented as a vio
  24 * device driver so that it can receive notification of vty-server lifetimes
  25 * after it registers with the vio bus to handle vty-server probe and remove
  26 * callbacks.
  27 *
  28 * Many vty-servers can be configured to connect to one vty, but a vty can
  29 * only be actively connected to by a single vty-server, in any manner, at one
  30 * time.  If the HMC is currently hosting the console for a target Linux
  31 * partition; attempts to open the tty device to the partition's console using
  32 * the hvcs on any partition will return -EBUSY with every open attempt until
  33 * the HMC frees the connection between its vty-server and the desired
  34 * partition's vty device.  Conversely, a vty-server may only be connected to
  35 * a single vty at one time even though it may have several configured vty
  36 * partner possibilities.
  37 *
  38 * Firmware does not provide notification of vty partner changes to this
  39 * driver.  This means that an HMC Super Admin may add or remove partner vtys
  40 * from a vty-server's partner list but the changes will not be signaled to
  41 * the vty-server.  Firmware only notifies the driver when a vty-server is
  42 * added or removed from the system.  To compensate for this deficiency, this
  43 * driver implements a sysfs update attribute which provides a method for
  44 * rescanning partner information upon a user's request.
  45 *
  46 * Each vty-server, prior to being exposed to this driver is reference counted
  47 * using the 2.6 Linux kernel kref construct.
  48 *
  49 * For direction on installation and usage of this driver please reference
  50 * Documentation/powerpc/hvcs.rst.
  51 */
  52
  53#include <linux/device.h>
  54#include <linux/init.h>
  55#include <linux/interrupt.h>
  56#include <linux/kernel.h>
  57#include <linux/kref.h>
  58#include <linux/kthread.h>
  59#include <linux/list.h>
  60#include <linux/major.h>
  61#include <linux/module.h>
  62#include <linux/moduleparam.h>
  63#include <linux/sched.h>
  64#include <linux/slab.h>
  65#include <linux/spinlock.h>
  66#include <linux/stat.h>
  67#include <linux/tty.h>
  68#include <linux/tty_flip.h>
  69#include <asm/hvconsole.h>
  70#include <asm/hvcserver.h>
  71#include <linux/uaccess.h>
  72#include <asm/vio.h>
  73
  74/*
  75 * 1.3.0 -> 1.3.1 In hvcs_open memset(..,0x00,..) instead of memset(..,0x3F,00).
  76 * Removed braces around single statements following conditionals.  Removed '=
  77 * 0' after static int declarations since these default to zero.  Removed
  78 * list_for_each_safe() and replaced with list_for_each_entry() in
  79 * hvcs_get_by_index().  The 'safe' version is un-needed now that the driver is
  80 * using spinlocks.  Changed spin_lock_irqsave() to spin_lock() when locking
  81 * hvcs_structs_lock and hvcs_pi_lock since these are not touched in an int
  82 * handler.  Initialized hvcs_structs_lock and hvcs_pi_lock to
  83 * SPIN_LOCK_UNLOCKED at declaration time rather than in hvcs_module_init().
  84 * Added spin_lock around list_del() in destroy_hvcs_struct() to protect the
  85 * list traversals from a deletion.  Removed '= NULL' from pointer declaration
  86 * statements since they are initialized NULL by default.  Removed wmb()
  87 * instances from hvcs_try_write().  They probably aren't needed with locking in
  88 * place.  Added check and cleanup for hvcs_pi_buff = kmalloc() in
  89 * hvcs_module_init().  Exposed hvcs_struct.index via a sysfs attribute so that
  90 * the coupling between /dev/hvcs* and a vty-server can be automatically
  91 * determined.  Moved kobject_put() in hvcs_open outside of the
  92 * spin_unlock_irqrestore().
  93 *
  94 * 1.3.1 -> 1.3.2 Changed method for determining hvcs_struct->index and had it
  95 * align with how the tty layer always assigns the lowest index available.  This
  96 * change resulted in a list of ints that denotes which indexes are available.
  97 * Device additions and removals use the new hvcs_get_index() and
  98 * hvcs_return_index() helper functions.  The list is created with
  99 * hvsc_alloc_index_list() and it is destroyed with hvcs_free_index_list().
 100 * Without these fixes hotplug vty-server adapter support goes crazy with this
 101 * driver if the user removes a vty-server adapter.  Moved free_irq() outside of
 102 * the hvcs_final_close() function in order to get it out of the spinlock.
 103 * Rearranged hvcs_close().  Cleaned up some printks and did some housekeeping
 104 * on the changelog.  Removed local CLC_LENGTH and used HVCS_CLC_LENGTH from
 105 * arch/powerepc/include/asm/hvcserver.h
 106 *
 107 * 1.3.2 -> 1.3.3 Replaced yield() in hvcs_close() with tty_wait_until_sent() to
 108 * prevent possible lockup with realtime scheduling as similarly pointed out by
 109 * akpm in hvc_console.  Changed resulted in the removal of hvcs_final_close()
 110 * to reorder cleanup operations and prevent discarding of pending data during
 111 * an hvcs_close().  Removed spinlock protection of hvcs_struct data members in
 112 * hvcs_write_room() and hvcs_chars_in_buffer() because they aren't needed.
 113 */
 114
 115#define HVCS_DRIVER_VERSION "1.3.3"
 116
 117MODULE_AUTHOR("Ryan S. Arnold <rsa@us.ibm.com>");
 118MODULE_DESCRIPTION("IBM hvcs (Hypervisor Virtual Console Server) Driver");
 119MODULE_LICENSE("GPL");
 120MODULE_VERSION(HVCS_DRIVER_VERSION);
 121
 122/*
 123 * Wait this long per iteration while trying to push buffered data to the
 124 * hypervisor before allowing the tty to complete a close operation.
 125 */
 126#define HVCS_CLOSE_WAIT (HZ/100) /* 1/10 of a second */
 127
 128/*
 129 * Since the Linux TTY code does not currently (2-04-2004) support dynamic
 130 * addition of tty derived devices and we shouldn't allocate thousands of
 131 * tty_device pointers when the number of vty-server & vty partner connections
 132 * will most often be much lower than this, we'll arbitrarily allocate
 133 * HVCS_DEFAULT_SERVER_ADAPTERS tty_structs and cdev's by default when we
 134 * register the tty_driver. This can be overridden using an insmod parameter.
 135 */
 136#define HVCS_DEFAULT_SERVER_ADAPTERS	64
 137
 138/*
 139 * The user can't insmod with more than HVCS_MAX_SERVER_ADAPTERS hvcs device
 140 * nodes as a sanity check.  Theoretically there can be over 1 Billion
 141 * vty-server & vty partner connections.
 142 */
 143#define HVCS_MAX_SERVER_ADAPTERS	1024
 144
 145/*
 146 * We let Linux assign us a major number and we start the minors at zero.  There
 147 * is no intuitive mapping between minor number and the target vty-server
 148 * adapter except that each new vty-server adapter is always assigned to the
 149 * smallest minor number available.
 150 */
 151#define HVCS_MINOR_START	0
 152
 153/*
 154 * The hcall interface involves putting 8 chars into each of two registers.
 155 * We load up those 2 registers (in arch/powerpc/platforms/pseries/hvconsole.c)
 156 * by casting char[16] to long[2].  It would work without __ALIGNED__, but a 
 157 * little (tiny) bit slower because an unaligned load is slower than aligned 
 158 * load.
 159 */
 160#define __ALIGNED__	__attribute__((__aligned__(8)))
 161
 162/*
 163 * How much data can firmware send with each hvc_put_chars()?  Maybe this
 164 * should be moved into an architecture specific area.
 165 */
 166#define HVCS_BUFF_LEN	16
 167
 168/*
 169 * This is the maximum amount of data we'll let the user send us (hvcs_write) at
 170 * once in a chunk as a sanity check.
 171 */
 172#define HVCS_MAX_FROM_USER	4096
 173
 174/*
 175 * Be careful when adding flags to this line discipline.  Don't add anything
 176 * that will cause echoing or we'll go into recursive loop echoing chars back
 177 * and forth with the console drivers.
 178 */
 179static const struct ktermios hvcs_tty_termios = {
 180	.c_iflag = IGNBRK | IGNPAR,
 181	.c_oflag = OPOST,
 182	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
 183	.c_cc = INIT_C_CC,
 184	.c_ispeed = 38400,
 185	.c_ospeed = 38400
 186};
 187
 188/*
 189 * This value is used to take the place of a command line parameter when the
 190 * module is inserted.  It starts as -1 and stays as such if the user doesn't
 191 * specify a module insmod parameter.  If they DO specify one then it is set to
 192 * the value of the integer passed in.
 193 */
 194static int hvcs_parm_num_devs = -1;
 195module_param(hvcs_parm_num_devs, int, 0);
 196
 197static const char hvcs_driver_name[] = "hvcs";
 198static const char hvcs_device_node[] = "hvcs";
 199static const char hvcs_driver_string[]
 200	= "IBM hvcs (Hypervisor Virtual Console Server) Driver";
 201
 202/* Status of partner info rescan triggered via sysfs. */
 203static int hvcs_rescan_status;
 204
 205static struct tty_driver *hvcs_tty_driver;
 206
 207/*
 208 * In order to be somewhat sane this driver always associates the hvcs_struct
 209 * index element with the numerically equal tty->index.  This means that a
 210 * hotplugged vty-server adapter will always map to the lowest index valued
 211 * device node.  If vty-servers were hotplug removed from the system and then
 212 * new ones added the new vty-server may have the largest slot number of all
 213 * the vty-server adapters in the partition but it may have the lowest dev node
 214 * index of all the adapters due to the hole left by the hotplug removed
 215 * adapter.  There are a set of functions provided to get the lowest index for
 216 * a new device as well as return the index to the list.  This list is allocated
 217 * with a number of elements equal to the number of device nodes requested when
 218 * the module was inserted.
 219 */
 220static int *hvcs_index_list;
 221
 222/*
 223 * How large is the list?  This is kept for traversal since the list is
 224 * dynamically created.
 225 */
 226static int hvcs_index_count;
 227
 228/*
 229 * Used by the khvcsd to pick up I/O operations when the kernel_thread is
 230 * already awake but potentially shifted to TASK_INTERRUPTIBLE state.
 231 */
 232static int hvcs_kicked;
 233
 234/*
 235 * Use by the kthread construct for task operations like waking the sleeping
 236 * thread and stopping the kthread.
 237 */
 238static struct task_struct *hvcs_task;
 239
 240/*
 241 * We allocate this for the use of all of the hvcs_structs when they fetch
 242 * partner info.
 243 */
 244static unsigned long *hvcs_pi_buff;
 245
 246/* Only allow one hvcs_struct to use the hvcs_pi_buff at a time. */
 247static DEFINE_SPINLOCK(hvcs_pi_lock);
 248
 249/* One vty-server per hvcs_struct */
 250struct hvcs_struct {
 251	struct tty_port port;
 252	spinlock_t lock;
 253
 254	/*
 255	 * This index identifies this hvcs device as the complement to a
 256	 * specific tty index.
 257	 */
 258	unsigned int index;
 259
 260	/*
 261	 * Used to tell the driver kernel_thread what operations need to take
 262	 * place upon this hvcs_struct instance.
 263	 */
 264	int todo_mask;
 265
 266	/*
 267	 * This buffer is required so that when hvcs_write_room() reports that
 268	 * it can send HVCS_BUFF_LEN characters that it will buffer the full
 269	 * HVCS_BUFF_LEN characters if need be.  This is essential for opost
 270	 * writes since they do not do high level buffering and expect to be
 271	 * able to send what the driver commits to sending buffering
 272	 * [e.g. tab to space conversions in n_tty.c opost()].
 273	 */
 274	char buffer[HVCS_BUFF_LEN];
 275	int chars_in_buffer;
 276
 277	/*
 278	 * Any variable below is valid before a tty is connected and
 279	 * stays valid after the tty is disconnected.  These shouldn't be
 280	 * whacked until the kobject refcount reaches zero though some entries
 281	 * may be changed via sysfs initiatives.
 282	 */
 283	int connected; /* is the vty-server currently connected to a vty? */
 284	uint32_t p_unit_address; /* partner unit address */
 285	uint32_t p_partition_ID; /* partner partition ID */
 286	char p_location_code[HVCS_CLC_LENGTH + 1]; /* CLC + Null Term */
 287	struct list_head next; /* list management */
 288	struct vio_dev *vdev;
 289};
 290
 291static LIST_HEAD(hvcs_structs);
 292static DEFINE_SPINLOCK(hvcs_structs_lock);
 293static DEFINE_MUTEX(hvcs_init_mutex);
 294
 295static void hvcs_unthrottle(struct tty_struct *tty);
 296static void hvcs_throttle(struct tty_struct *tty);
 297static irqreturn_t hvcs_handle_interrupt(int irq, void *dev_instance);
 298
 299static int hvcs_write(struct tty_struct *tty,
 300		const unsigned char *buf, int count);
 301static int hvcs_write_room(struct tty_struct *tty);
 302static int hvcs_chars_in_buffer(struct tty_struct *tty);
 303
 304static int hvcs_has_pi(struct hvcs_struct *hvcsd);
 305static void hvcs_set_pi(struct hvcs_partner_info *pi,
 306		struct hvcs_struct *hvcsd);
 307static int hvcs_get_pi(struct hvcs_struct *hvcsd);
 308static int hvcs_rescan_devices_list(void);
 309
 310static int hvcs_partner_connect(struct hvcs_struct *hvcsd);
 311static void hvcs_partner_free(struct hvcs_struct *hvcsd);
 312
 313static int hvcs_enable_device(struct hvcs_struct *hvcsd,
 314		uint32_t unit_address, unsigned int irq, struct vio_dev *dev);
 315
 316static int hvcs_open(struct tty_struct *tty, struct file *filp);
 317static void hvcs_close(struct tty_struct *tty, struct file *filp);
 318static void hvcs_hangup(struct tty_struct * tty);
 319
 320static int hvcs_probe(struct vio_dev *dev,
 321		const struct vio_device_id *id);
 322static int hvcs_remove(struct vio_dev *dev);
 323static int __init hvcs_module_init(void);
 324static void __exit hvcs_module_exit(void);
 325static int hvcs_initialize(void);
 326
 327#define HVCS_SCHED_READ	0x00000001
 328#define HVCS_QUICK_READ	0x00000002
 329#define HVCS_TRY_WRITE	0x00000004
 330#define HVCS_READ_MASK	(HVCS_SCHED_READ | HVCS_QUICK_READ)
 331
 332static inline struct hvcs_struct *from_vio_dev(struct vio_dev *viod)
 333{
 334	return dev_get_drvdata(&viod->dev);
 335}
 336/* The sysfs interface for the driver and devices */
 337
 338static ssize_t hvcs_partner_vtys_show(struct device *dev, struct device_attribute *attr, char *buf)
 339{
 340	struct vio_dev *viod = to_vio_dev(dev);
 341	struct hvcs_struct *hvcsd = from_vio_dev(viod);
 342	unsigned long flags;
 343	int retval;
 344
 345	spin_lock_irqsave(&hvcsd->lock, flags);
 346	retval = sprintf(buf, "%X\n", hvcsd->p_unit_address);
 347	spin_unlock_irqrestore(&hvcsd->lock, flags);
 348	return retval;
 349}
 350static DEVICE_ATTR(partner_vtys, S_IRUGO, hvcs_partner_vtys_show, NULL);
 351
 352static ssize_t hvcs_partner_clcs_show(struct device *dev, struct device_attribute *attr, char *buf)
 353{
 354	struct vio_dev *viod = to_vio_dev(dev);
 355	struct hvcs_struct *hvcsd = from_vio_dev(viod);
 356	unsigned long flags;
 357	int retval;
 358
 359	spin_lock_irqsave(&hvcsd->lock, flags);
 360	retval = sprintf(buf, "%s\n", &hvcsd->p_location_code[0]);
 361	spin_unlock_irqrestore(&hvcsd->lock, flags);
 362	return retval;
 363}
 364static DEVICE_ATTR(partner_clcs, S_IRUGO, hvcs_partner_clcs_show, NULL);
 365
 366static ssize_t hvcs_current_vty_store(struct device *dev, struct device_attribute *attr, const char * buf,
 367		size_t count)
 368{
 369	/*
 370	 * Don't need this feature at the present time because firmware doesn't
 371	 * yet support multiple partners.
 372	 */
 373	printk(KERN_INFO "HVCS: Denied current_vty change: -EPERM.\n");
 374	return -EPERM;
 375}
 376
 377static ssize_t hvcs_current_vty_show(struct device *dev, struct device_attribute *attr, char *buf)
 378{
 379	struct vio_dev *viod = to_vio_dev(dev);
 380	struct hvcs_struct *hvcsd = from_vio_dev(viod);
 381	unsigned long flags;
 382	int retval;
 383
 384	spin_lock_irqsave(&hvcsd->lock, flags);
 385	retval = sprintf(buf, "%s\n", &hvcsd->p_location_code[0]);
 386	spin_unlock_irqrestore(&hvcsd->lock, flags);
 387	return retval;
 388}
 389
 390static DEVICE_ATTR(current_vty,
 391	S_IRUGO | S_IWUSR, hvcs_current_vty_show, hvcs_current_vty_store);
 392
 393static ssize_t hvcs_vterm_state_store(struct device *dev, struct device_attribute *attr, const char *buf,
 394		size_t count)
 395{
 396	struct vio_dev *viod = to_vio_dev(dev);
 397	struct hvcs_struct *hvcsd = from_vio_dev(viod);
 398	unsigned long flags;
 399
 400	/* writing a '0' to this sysfs entry will result in the disconnect. */
 401	if (simple_strtol(buf, NULL, 0) != 0)
 402		return -EINVAL;
 403
 404	spin_lock_irqsave(&hvcsd->lock, flags);
 405
 406	if (hvcsd->port.count > 0) {
 407		spin_unlock_irqrestore(&hvcsd->lock, flags);
 408		printk(KERN_INFO "HVCS: vterm state unchanged.  "
 409				"The hvcs device node is still in use.\n");
 410		return -EPERM;
 411	}
 412
 413	if (hvcsd->connected == 0) {
 414		spin_unlock_irqrestore(&hvcsd->lock, flags);
 415		printk(KERN_INFO "HVCS: vterm state unchanged. The"
 416				" vty-server is not connected to a vty.\n");
 417		return -EPERM;
 418	}
 419
 420	hvcs_partner_free(hvcsd);
 421	printk(KERN_INFO "HVCS: Closed vty-server@%X and"
 422			" partner vty@%X:%d connection.\n",
 423			hvcsd->vdev->unit_address,
 424			hvcsd->p_unit_address,
 425			(uint32_t)hvcsd->p_partition_ID);
 426
 427	spin_unlock_irqrestore(&hvcsd->lock, flags);
 428	return count;
 429}
 430
 431static ssize_t hvcs_vterm_state_show(struct device *dev, struct device_attribute *attr, char *buf)
 432{
 433	struct vio_dev *viod = to_vio_dev(dev);
 434	struct hvcs_struct *hvcsd = from_vio_dev(viod);
 435	unsigned long flags;
 436	int retval;
 437
 438	spin_lock_irqsave(&hvcsd->lock, flags);
 439	retval = sprintf(buf, "%d\n", hvcsd->connected);
 440	spin_unlock_irqrestore(&hvcsd->lock, flags);
 441	return retval;
 442}
 443static DEVICE_ATTR(vterm_state, S_IRUGO | S_IWUSR,
 444		hvcs_vterm_state_show, hvcs_vterm_state_store);
 445
 446static ssize_t hvcs_index_show(struct device *dev, struct device_attribute *attr, char *buf)
 447{
 448	struct vio_dev *viod = to_vio_dev(dev);
 449	struct hvcs_struct *hvcsd = from_vio_dev(viod);
 450	unsigned long flags;
 451	int retval;
 452
 453	spin_lock_irqsave(&hvcsd->lock, flags);
 454	retval = sprintf(buf, "%d\n", hvcsd->index);
 455	spin_unlock_irqrestore(&hvcsd->lock, flags);
 456	return retval;
 457}
 458
 459static DEVICE_ATTR(index, S_IRUGO, hvcs_index_show, NULL);
 460
 461static struct attribute *hvcs_attrs[] = {
 462	&dev_attr_partner_vtys.attr,
 463	&dev_attr_partner_clcs.attr,
 464	&dev_attr_current_vty.attr,
 465	&dev_attr_vterm_state.attr,
 466	&dev_attr_index.attr,
 467	NULL,
 468};
 469
 470static struct attribute_group hvcs_attr_group = {
 471	.attrs = hvcs_attrs,
 472};
 473
 474static ssize_t rescan_show(struct device_driver *ddp, char *buf)
 475{
 476	/* A 1 means it is updating, a 0 means it is done updating */
 477	return snprintf(buf, PAGE_SIZE, "%d\n", hvcs_rescan_status);
 478}
 479
 480static ssize_t rescan_store(struct device_driver *ddp, const char * buf,
 481		size_t count)
 482{
 483	if ((simple_strtol(buf, NULL, 0) != 1)
 484		&& (hvcs_rescan_status != 0))
 485		return -EINVAL;
 486
 487	hvcs_rescan_status = 1;
 488	printk(KERN_INFO "HVCS: rescanning partner info for all"
 489		" vty-servers.\n");
 490	hvcs_rescan_devices_list();
 491	hvcs_rescan_status = 0;
 492	return count;
 493}
 494
 495static DRIVER_ATTR_RW(rescan);
 496
 497static void hvcs_kick(void)
 498{
 499	hvcs_kicked = 1;
 500	wmb();
 501	wake_up_process(hvcs_task);
 502}
 503
 504static void hvcs_unthrottle(struct tty_struct *tty)
 505{
 506	struct hvcs_struct *hvcsd = tty->driver_data;
 507	unsigned long flags;
 508
 509	spin_lock_irqsave(&hvcsd->lock, flags);
 510	hvcsd->todo_mask |= HVCS_SCHED_READ;
 511	spin_unlock_irqrestore(&hvcsd->lock, flags);
 512	hvcs_kick();
 513}
 514
 515static void hvcs_throttle(struct tty_struct *tty)
 516{
 517	struct hvcs_struct *hvcsd = tty->driver_data;
 518	unsigned long flags;
 519
 520	spin_lock_irqsave(&hvcsd->lock, flags);
 521	vio_disable_interrupts(hvcsd->vdev);
 522	spin_unlock_irqrestore(&hvcsd->lock, flags);
 523}
 524
 525/*
 526 * If the device is being removed we don't have to worry about this interrupt
 527 * handler taking any further interrupts because they are disabled which means
 528 * the hvcs_struct will always be valid in this handler.
 529 */
 530static irqreturn_t hvcs_handle_interrupt(int irq, void *dev_instance)
 531{
 532	struct hvcs_struct *hvcsd = dev_instance;
 533
 534	spin_lock(&hvcsd->lock);
 535	vio_disable_interrupts(hvcsd->vdev);
 536	hvcsd->todo_mask |= HVCS_SCHED_READ;
 537	spin_unlock(&hvcsd->lock);
 538	hvcs_kick();
 539
 540	return IRQ_HANDLED;
 541}
 542
 543/* This function must be called with the hvcsd->lock held */
 544static void hvcs_try_write(struct hvcs_struct *hvcsd)
 545{
 546	uint32_t unit_address = hvcsd->vdev->unit_address;
 547	struct tty_struct *tty = hvcsd->port.tty;
 548	int sent;
 549
 550	if (hvcsd->todo_mask & HVCS_TRY_WRITE) {
 551		/* won't send partial writes */
 552		sent = hvc_put_chars(unit_address,
 553				&hvcsd->buffer[0],
 554				hvcsd->chars_in_buffer );
 555		if (sent > 0) {
 556			hvcsd->chars_in_buffer = 0;
 557			/* wmb(); */
 558			hvcsd->todo_mask &= ~(HVCS_TRY_WRITE);
 559			/* wmb(); */
 560
 561			/*
 562			 * We are still obligated to deliver the data to the
 563			 * hypervisor even if the tty has been closed because
 564			 * we committed to delivering it.  But don't try to wake
 565			 * a non-existent tty.
 566			 */
 567			if (tty) {
 568				tty_wakeup(tty);
 569			}
 570		}
 571	}
 572}
 573
 574static int hvcs_io(struct hvcs_struct *hvcsd)
 575{
 576	uint32_t unit_address;
 577	struct tty_struct *tty;
 578	char buf[HVCS_BUFF_LEN] __ALIGNED__;
 579	unsigned long flags;
 580	int got = 0;
 581
 582	spin_lock_irqsave(&hvcsd->lock, flags);
 583
 584	unit_address = hvcsd->vdev->unit_address;
 585	tty = hvcsd->port.tty;
 586
 587	hvcs_try_write(hvcsd);
 588
 589	if (!tty || tty_throttled(tty)) {
 590		hvcsd->todo_mask &= ~(HVCS_READ_MASK);
 591		goto bail;
 592	} else if (!(hvcsd->todo_mask & (HVCS_READ_MASK)))
 593		goto bail;
 594
 595	/* remove the read masks */
 596	hvcsd->todo_mask &= ~(HVCS_READ_MASK);
 597
 598	if (tty_buffer_request_room(&hvcsd->port, HVCS_BUFF_LEN) >= HVCS_BUFF_LEN) {
 599		got = hvc_get_chars(unit_address,
 600				&buf[0],
 601				HVCS_BUFF_LEN);
 602		tty_insert_flip_string(&hvcsd->port, buf, got);
 603	}
 604
 605	/* Give the TTY time to process the data we just sent. */
 606	if (got)
 607		hvcsd->todo_mask |= HVCS_QUICK_READ;
 608
 609	spin_unlock_irqrestore(&hvcsd->lock, flags);
 610	/* This is synch because tty->low_latency == 1 */
 611	if(got)
 612		tty_flip_buffer_push(&hvcsd->port);
 613
 614	if (!got) {
 615		/* Do this _after_ the flip_buffer_push */
 616		spin_lock_irqsave(&hvcsd->lock, flags);
 617		vio_enable_interrupts(hvcsd->vdev);
 618		spin_unlock_irqrestore(&hvcsd->lock, flags);
 619	}
 620
 621	return hvcsd->todo_mask;
 622
 623 bail:
 624	spin_unlock_irqrestore(&hvcsd->lock, flags);
 625	return hvcsd->todo_mask;
 626}
 627
 628static int khvcsd(void *unused)
 629{
 630	struct hvcs_struct *hvcsd;
 631	int hvcs_todo_mask;
 632
 633	__set_current_state(TASK_RUNNING);
 634
 635	do {
 636		hvcs_todo_mask = 0;
 637		hvcs_kicked = 0;
 638		wmb();
 639
 640		spin_lock(&hvcs_structs_lock);
 641		list_for_each_entry(hvcsd, &hvcs_structs, next) {
 642			hvcs_todo_mask |= hvcs_io(hvcsd);
 643		}
 644		spin_unlock(&hvcs_structs_lock);
 645
 646		/*
 647		 * If any of the hvcs adapters want to try a write or quick read
 648		 * don't schedule(), yield a smidgen then execute the hvcs_io
 649		 * thread again for those that want the write.
 650		 */
 651		 if (hvcs_todo_mask & (HVCS_TRY_WRITE | HVCS_QUICK_READ)) {
 652			yield();
 653			continue;
 654		}
 655
 656		set_current_state(TASK_INTERRUPTIBLE);
 657		if (!hvcs_kicked)
 658			schedule();
 659		__set_current_state(TASK_RUNNING);
 660	} while (!kthread_should_stop());
 661
 662	return 0;
 663}
 664
 665static const struct vio_device_id hvcs_driver_table[] = {
 666	{"serial-server", "hvterm2"},
 667	{ "", "" }
 668};
 669MODULE_DEVICE_TABLE(vio, hvcs_driver_table);
 670
 671static void hvcs_return_index(int index)
 672{
 673	/* Paranoia check */
 674	if (!hvcs_index_list)
 675		return;
 676	if (index < 0 || index >= hvcs_index_count)
 677		return;
 678	if (hvcs_index_list[index] == -1)
 679		return;
 680	else
 681		hvcs_index_list[index] = -1;
 682}
 683
 684static void hvcs_destruct_port(struct tty_port *p)
 685{
 686	struct hvcs_struct *hvcsd = container_of(p, struct hvcs_struct, port);
 687	struct vio_dev *vdev;
 688	unsigned long flags;
 689
 690	spin_lock(&hvcs_structs_lock);
 691	spin_lock_irqsave(&hvcsd->lock, flags);
 692
 693	/* the list_del poisons the pointers */
 694	list_del(&(hvcsd->next));
 695
 696	if (hvcsd->connected == 1) {
 697		hvcs_partner_free(hvcsd);
 698		printk(KERN_INFO "HVCS: Closed vty-server@%X and"
 699				" partner vty@%X:%d connection.\n",
 700				hvcsd->vdev->unit_address,
 701				hvcsd->p_unit_address,
 702				(uint32_t)hvcsd->p_partition_ID);
 703	}
 704	printk(KERN_INFO "HVCS: Destroyed hvcs_struct for vty-server@%X.\n",
 705			hvcsd->vdev->unit_address);
 706
 707	vdev = hvcsd->vdev;
 708	hvcsd->vdev = NULL;
 709
 710	hvcsd->p_unit_address = 0;
 711	hvcsd->p_partition_ID = 0;
 712	hvcs_return_index(hvcsd->index);
 713	memset(&hvcsd->p_location_code[0], 0x00, HVCS_CLC_LENGTH + 1);
 714
 715	spin_unlock_irqrestore(&hvcsd->lock, flags);
 716	spin_unlock(&hvcs_structs_lock);
 717
 718	sysfs_remove_group(&vdev->dev.kobj, &hvcs_attr_group);
 719
 720	kfree(hvcsd);
 721}
 722
 723static const struct tty_port_operations hvcs_port_ops = {
 724	.destruct = hvcs_destruct_port,
 725};
 726
 727static int hvcs_get_index(void)
 728{
 729	int i;
 730	/* Paranoia check */
 731	if (!hvcs_index_list) {
 732		printk(KERN_ERR "HVCS: hvcs_index_list NOT valid!.\n");
 733		return -EFAULT;
 734	}
 735	/* Find the numerically lowest first free index. */
 736	for(i = 0; i < hvcs_index_count; i++) {
 737		if (hvcs_index_list[i] == -1) {
 738			hvcs_index_list[i] = 0;
 739			return i;
 740		}
 741	}
 742	return -1;
 743}
 744
 745static int hvcs_probe(
 746	struct vio_dev *dev,
 747	const struct vio_device_id *id)
 748{
 749	struct hvcs_struct *hvcsd;
 750	int index, rc;
 751	int retval;
 752
 753	if (!dev || !id) {
 754		printk(KERN_ERR "HVCS: probed with invalid parameter.\n");
 755		return -EPERM;
 756	}
 757
 758	/* Make sure we are properly initialized */
 759	rc = hvcs_initialize();
 760	if (rc) {
 761		pr_err("HVCS: Failed to initialize core driver.\n");
 762		return rc;
 763	}
 764
 765	/* early to avoid cleanup on failure */
 766	index = hvcs_get_index();
 767	if (index < 0) {
 768		return -EFAULT;
 769	}
 770
 771	hvcsd = kzalloc(sizeof(*hvcsd), GFP_KERNEL);
 772	if (!hvcsd)
 773		return -ENODEV;
 774
 775	tty_port_init(&hvcsd->port);
 776	hvcsd->port.ops = &hvcs_port_ops;
 777	spin_lock_init(&hvcsd->lock);
 778
 779	hvcsd->vdev = dev;
 780	dev_set_drvdata(&dev->dev, hvcsd);
 781
 782	hvcsd->index = index;
 783
 784	/* hvcsd->index = ++hvcs_struct_count; */
 785	hvcsd->chars_in_buffer = 0;
 786	hvcsd->todo_mask = 0;
 787	hvcsd->connected = 0;
 788
 789	/*
 790	 * This will populate the hvcs_struct's partner info fields for the
 791	 * first time.
 792	 */
 793	if (hvcs_get_pi(hvcsd)) {
 794		printk(KERN_ERR "HVCS: Failed to fetch partner"
 795			" info for vty-server@%X on device probe.\n",
 796			hvcsd->vdev->unit_address);
 797	}
 798
 799	/*
 800	 * If a user app opens a tty that corresponds to this vty-server before
 801	 * the hvcs_struct has been added to the devices list then the user app
 802	 * will get -ENODEV.
 803	 */
 804	spin_lock(&hvcs_structs_lock);
 805	list_add_tail(&(hvcsd->next), &hvcs_structs);
 806	spin_unlock(&hvcs_structs_lock);
 807
 808	retval = sysfs_create_group(&dev->dev.kobj, &hvcs_attr_group);
 809	if (retval) {
 810		printk(KERN_ERR "HVCS: Can't create sysfs attrs for vty-server@%X\n",
 811		       hvcsd->vdev->unit_address);
 812		return retval;
 813	}
 814
 815	printk(KERN_INFO "HVCS: vty-server@%X added to the vio bus.\n", dev->unit_address);
 816
 817	/*
 818	 * DON'T enable interrupts here because there is no user to receive the
 819	 * data.
 820	 */
 821	return 0;
 822}
 823
 824static int hvcs_remove(struct vio_dev *dev)
 825{
 826	struct hvcs_struct *hvcsd = dev_get_drvdata(&dev->dev);
 827	unsigned long flags;
 828	struct tty_struct *tty;
 829
 830	if (!hvcsd)
 831		return -ENODEV;
 832
 833	/* By this time the vty-server won't be getting any more interrupts */
 834
 835	spin_lock_irqsave(&hvcsd->lock, flags);
 836
 837	tty = hvcsd->port.tty;
 838
 839	spin_unlock_irqrestore(&hvcsd->lock, flags);
 840
 841	/*
 842	 * Let the last holder of this object cause it to be removed, which
 843	 * would probably be tty_hangup below.
 844	 */
 845	tty_port_put(&hvcsd->port);
 846
 847	/*
 848	 * The hangup is a scheduled function which will auto chain call
 849	 * hvcs_hangup.  The tty should always be valid at this time unless a
 850	 * simultaneous tty close already cleaned up the hvcs_struct.
 851	 */
 852	if (tty)
 853		tty_hangup(tty);
 854
 855	printk(KERN_INFO "HVCS: vty-server@%X removed from the"
 856			" vio bus.\n", dev->unit_address);
 857	return 0;
 858};
 859
 860static struct vio_driver hvcs_vio_driver = {
 861	.id_table	= hvcs_driver_table,
 862	.probe		= hvcs_probe,
 863	.remove		= hvcs_remove,
 864	.name		= hvcs_driver_name,
 865};
 866
 867/* Only called from hvcs_get_pi please */
 868static void hvcs_set_pi(struct hvcs_partner_info *pi, struct hvcs_struct *hvcsd)
 869{
 870	hvcsd->p_unit_address = pi->unit_address;
 871	hvcsd->p_partition_ID  = pi->partition_ID;
 872
 873	/* copy the null-term char too */
 874	strlcpy(hvcsd->p_location_code, pi->location_code,
 875		sizeof(hvcsd->p_location_code));
 876}
 877
 878/*
 879 * Traverse the list and add the partner info that is found to the hvcs_struct
 880 * struct entry. NOTE: At this time I know that partner info will return a
 881 * single entry but in the future there may be multiple partner info entries per
 882 * vty-server and you'll want to zero out that list and reset it.  If for some
 883 * reason you have an old version of this driver but there IS more than one
 884 * partner info then hvcsd->p_* will hold the last partner info data from the
 885 * firmware query.  A good way to update this code would be to replace the three
 886 * partner info fields in hvcs_struct with a list of hvcs_partner_info
 887 * instances.
 888 *
 889 * This function must be called with the hvcsd->lock held.
 890 */
 891static int hvcs_get_pi(struct hvcs_struct *hvcsd)
 892{
 893	struct hvcs_partner_info *pi;
 894	uint32_t unit_address = hvcsd->vdev->unit_address;
 895	struct list_head head;
 896	int retval;
 897
 898	spin_lock(&hvcs_pi_lock);
 899	if (!hvcs_pi_buff) {
 900		spin_unlock(&hvcs_pi_lock);
 901		return -EFAULT;
 902	}
 903	retval = hvcs_get_partner_info(unit_address, &head, hvcs_pi_buff);
 904	spin_unlock(&hvcs_pi_lock);
 905	if (retval) {
 906		printk(KERN_ERR "HVCS: Failed to fetch partner"
 907			" info for vty-server@%x.\n", unit_address);
 908		return retval;
 909	}
 910
 911	/* nixes the values if the partner vty went away */
 912	hvcsd->p_unit_address = 0;
 913	hvcsd->p_partition_ID = 0;
 914
 915	list_for_each_entry(pi, &head, node)
 916		hvcs_set_pi(pi, hvcsd);
 917
 918	hvcs_free_partner_info(&head);
 919	return 0;
 920}
 921
 922/*
 923 * This function is executed by the driver "rescan" sysfs entry.  It shouldn't
 924 * be executed elsewhere, in order to prevent deadlock issues.
 925 */
 926static int hvcs_rescan_devices_list(void)
 927{
 928	struct hvcs_struct *hvcsd;
 929	unsigned long flags;
 930
 931	spin_lock(&hvcs_structs_lock);
 932
 933	list_for_each_entry(hvcsd, &hvcs_structs, next) {
 934		spin_lock_irqsave(&hvcsd->lock, flags);
 935		hvcs_get_pi(hvcsd);
 936		spin_unlock_irqrestore(&hvcsd->lock, flags);
 937	}
 938
 939	spin_unlock(&hvcs_structs_lock);
 940
 941	return 0;
 942}
 943
 944/*
 945 * Farm this off into its own function because it could be more complex once
 946 * multiple partners support is added. This function should be called with
 947 * the hvcsd->lock held.
 948 */
 949static int hvcs_has_pi(struct hvcs_struct *hvcsd)
 950{
 951	if ((!hvcsd->p_unit_address) || (!hvcsd->p_partition_ID))
 952		return 0;
 953	return 1;
 954}
 955
 956/*
 957 * NOTE: It is possible that the super admin removed a partner vty and then
 958 * added a different vty as the new partner.
 959 *
 960 * This function must be called with the hvcsd->lock held.
 961 */
 962static int hvcs_partner_connect(struct hvcs_struct *hvcsd)
 963{
 964	int retval;
 965	unsigned int unit_address = hvcsd->vdev->unit_address;
 966
 967	/*
 968	 * If there wasn't any pi when the device was added it doesn't meant
 969	 * there isn't any now.  This driver isn't notified when a new partner
 970	 * vty is added to a vty-server so we discover changes on our own.
 971	 * Please see comments in hvcs_register_connection() for justification
 972	 * of this bizarre code.
 973	 */
 974	retval = hvcs_register_connection(unit_address,
 975			hvcsd->p_partition_ID,
 976			hvcsd->p_unit_address);
 977	if (!retval) {
 978		hvcsd->connected = 1;
 979		return 0;
 980	} else if (retval != -EINVAL)
 981		return retval;
 982
 983	/*
 984	 * As per the spec re-get the pi and try again if -EINVAL after the
 985	 * first connection attempt.
 986	 */
 987	if (hvcs_get_pi(hvcsd))
 988		return -ENOMEM;
 989
 990	if (!hvcs_has_pi(hvcsd))
 991		return -ENODEV;
 992
 993	retval = hvcs_register_connection(unit_address,
 994			hvcsd->p_partition_ID,
 995			hvcsd->p_unit_address);
 996	if (retval != -EINVAL) {
 997		hvcsd->connected = 1;
 998		return retval;
 999	}
1000
1001	/*
1002	 * EBUSY is the most likely scenario though the vty could have been
1003	 * removed or there really could be an hcall error due to the parameter
1004	 * data but thanks to ambiguous firmware return codes we can't really
1005	 * tell.
1006	 */
1007	printk(KERN_INFO "HVCS: vty-server or partner"
1008			" vty is busy.  Try again later.\n");
1009	return -EBUSY;
1010}
1011
1012/* This function must be called with the hvcsd->lock held */
1013static void hvcs_partner_free(struct hvcs_struct *hvcsd)
1014{
1015	int retval;
1016	do {
1017		retval = hvcs_free_connection(hvcsd->vdev->unit_address);
1018	} while (retval == -EBUSY);
1019	hvcsd->connected = 0;
1020}
1021
1022/* This helper function must be called WITHOUT the hvcsd->lock held */
1023static int hvcs_enable_device(struct hvcs_struct *hvcsd, uint32_t unit_address,
1024		unsigned int irq, struct vio_dev *vdev)
1025{
1026	unsigned long flags;
1027	int rc;
1028
1029	/*
1030	 * It is possible that the vty-server was removed between the time that
1031	 * the conn was registered and now.
1032	 */
1033	rc = request_irq(irq, &hvcs_handle_interrupt, 0, "ibmhvcs", hvcsd);
1034	if (!rc) {
1035		/*
1036		 * It is possible the vty-server was removed after the irq was
1037		 * requested but before we have time to enable interrupts.
1038		 */
1039		if (vio_enable_interrupts(vdev) == H_SUCCESS)
1040			return 0;
1041		else {
1042			printk(KERN_ERR "HVCS: int enable failed for"
1043					" vty-server@%X.\n", unit_address);
1044			free_irq(irq, hvcsd);
1045		}
1046	} else
1047		printk(KERN_ERR "HVCS: irq req failed for"
1048				" vty-server@%X.\n", unit_address);
1049
1050	spin_lock_irqsave(&hvcsd->lock, flags);
1051	hvcs_partner_free(hvcsd);
1052	spin_unlock_irqrestore(&hvcsd->lock, flags);
1053
1054	return rc;
1055
1056}
1057
1058/*
1059 * This always increments the kref ref count if the call is successful.
1060 * Please remember to dec when you are done with the instance.
1061 *
1062 * NOTICE: Do NOT hold either the hvcs_struct.lock or hvcs_structs_lock when
1063 * calling this function or you will get deadlock.
1064 */
1065static struct hvcs_struct *hvcs_get_by_index(int index)
1066{
1067	struct hvcs_struct *hvcsd;
1068	unsigned long flags;
1069
1070	spin_lock(&hvcs_structs_lock);
1071	list_for_each_entry(hvcsd, &hvcs_structs, next) {
1072		spin_lock_irqsave(&hvcsd->lock, flags);
1073		if (hvcsd->index == index) {
1074			tty_port_get(&hvcsd->port);
1075			spin_unlock_irqrestore(&hvcsd->lock, flags);
1076			spin_unlock(&hvcs_structs_lock);
1077			return hvcsd;
1078		}
1079		spin_unlock_irqrestore(&hvcsd->lock, flags);
1080	}
1081	spin_unlock(&hvcs_structs_lock);
1082
1083	return NULL;
1084}
1085
1086static int hvcs_install(struct tty_driver *driver, struct tty_struct *tty)
1087{
1088	struct hvcs_struct *hvcsd;
1089	struct vio_dev *vdev;
1090	unsigned long unit_address, flags;
1091	unsigned int irq;
1092	int retval;
1093
1094	/*
1095	 * Is there a vty-server that shares the same index?
1096	 * This function increments the kref index.
1097	 */
1098	hvcsd = hvcs_get_by_index(tty->index);
1099	if (!hvcsd) {
1100		printk(KERN_WARNING "HVCS: open failed, no device associated"
1101				" with tty->index %d.\n", tty->index);
1102		return -ENODEV;
1103	}
1104
1105	spin_lock_irqsave(&hvcsd->lock, flags);
1106
1107	if (hvcsd->connected == 0) {
1108		retval = hvcs_partner_connect(hvcsd);
1109		if (retval) {
1110			spin_unlock_irqrestore(&hvcsd->lock, flags);
1111			printk(KERN_WARNING "HVCS: partner connect failed.\n");
1112			goto err_put;
1113		}
1114	}
1115
1116	hvcsd->port.count = 0;
1117	hvcsd->port.tty = tty;
1118	tty->driver_data = hvcsd;
1119
1120	memset(&hvcsd->buffer[0], 0x00, HVCS_BUFF_LEN);
1121
1122	/*
1123	 * Save these in the spinlock for the enable operations that need them
1124	 * outside of the spinlock.
1125	 */
1126	irq = hvcsd->vdev->irq;
1127	vdev = hvcsd->vdev;
1128	unit_address = hvcsd->vdev->unit_address;
1129
1130	hvcsd->todo_mask |= HVCS_SCHED_READ;
1131	spin_unlock_irqrestore(&hvcsd->lock, flags);
1132
1133	/*
1134	 * This must be done outside of the spinlock because it requests irqs
1135	 * and will grab the spinlock and free the connection if it fails.
1136	 */
1137	retval = hvcs_enable_device(hvcsd, unit_address, irq, vdev);
1138	if (retval) {
1139		printk(KERN_WARNING "HVCS: enable device failed.\n");
1140		goto err_put;
1141	}
1142
1143	retval = tty_port_install(&hvcsd->port, driver, tty);
1144	if (retval)
1145		goto err_irq;
1146
1147	return 0;
1148err_irq:
1149	spin_lock_irqsave(&hvcsd->lock, flags);
1150	vio_disable_interrupts(hvcsd->vdev);
1151	spin_unlock_irqrestore(&hvcsd->lock, flags);
1152	free_irq(irq, hvcsd);
1153err_put:
1154	tty_port_put(&hvcsd->port);
1155
1156	return retval;
1157}
1158
1159/*
1160 * This is invoked via the tty_open interface when a user app connects to the
1161 * /dev node.
1162 */
1163static int hvcs_open(struct tty_struct *tty, struct file *filp)
1164{
1165	struct hvcs_struct *hvcsd = tty->driver_data;
1166	unsigned long flags;
1167
1168	spin_lock_irqsave(&hvcsd->lock, flags);
1169	hvcsd->port.count++;
1170	hvcsd->todo_mask |= HVCS_SCHED_READ;
1171	spin_unlock_irqrestore(&hvcsd->lock, flags);
1172
1173	hvcs_kick();
1174
1175	printk(KERN_INFO "HVCS: vty-server@%X connection opened.\n",
1176		hvcsd->vdev->unit_address );
1177
1178	return 0;
1179}
1180
1181static void hvcs_close(struct tty_struct *tty, struct file *filp)
1182{
1183	struct hvcs_struct *hvcsd;
1184	unsigned long flags;
1185	int irq;
1186
1187	/*
1188	 * Is someone trying to close the file associated with this device after
1189	 * we have hung up?  If so tty->driver_data wouldn't be valid.
1190	 */
1191	if (tty_hung_up_p(filp))
1192		return;
1193
1194	/*
1195	 * No driver_data means that this close was probably issued after a
1196	 * failed hvcs_open by the tty layer's release_dev() api and we can just
1197	 * exit cleanly.
1198	 */
1199	if (!tty->driver_data)
1200		return;
1201
1202	hvcsd = tty->driver_data;
1203
1204	spin_lock_irqsave(&hvcsd->lock, flags);
1205	if (--hvcsd->port.count == 0) {
1206
1207		vio_disable_interrupts(hvcsd->vdev);
1208
1209		/*
1210		 * NULL this early so that the kernel_thread doesn't try to
1211		 * execute any operations on the TTY even though it is obligated
1212		 * to deliver any pending I/O to the hypervisor.
1213		 */
1214		hvcsd->port.tty = NULL;
1215
1216		irq = hvcsd->vdev->irq;
1217		spin_unlock_irqrestore(&hvcsd->lock, flags);
1218
1219		tty_wait_until_sent(tty, HVCS_CLOSE_WAIT);
1220
1221		/*
1222		 * This line is important because it tells hvcs_open that this
1223		 * device needs to be re-configured the next time hvcs_open is
1224		 * called.
1225		 */
1226		tty->driver_data = NULL;
1227
1228		free_irq(irq, hvcsd);
1229		return;
1230	} else if (hvcsd->port.count < 0) {
1231		printk(KERN_ERR "HVCS: vty-server@%X open_count: %d is mismanaged.\n",
1232		hvcsd->vdev->unit_address, hvcsd->port.count);
1233	}
1234
1235	spin_unlock_irqrestore(&hvcsd->lock, flags);
1236}
1237
1238static void hvcs_cleanup(struct tty_struct * tty)
1239{
1240	struct hvcs_struct *hvcsd = tty->driver_data;
1241
1242	tty_port_put(&hvcsd->port);
1243}
1244
1245static void hvcs_hangup(struct tty_struct * tty)
1246{
1247	struct hvcs_struct *hvcsd = tty->driver_data;
1248	unsigned long flags;
1249	int temp_open_count;
1250	int irq;
1251
1252	spin_lock_irqsave(&hvcsd->lock, flags);
1253	/* Preserve this so that we know how many kref refs to put */
1254	temp_open_count = hvcsd->port.count;
1255
1256	/*
1257	 * Don't kref put inside the spinlock because the destruction
1258	 * callback may use the spinlock and it may get called before the
1259	 * spinlock has been released.
1260	 */
1261	vio_disable_interrupts(hvcsd->vdev);
1262
1263	hvcsd->todo_mask = 0;
1264
1265	/* I don't think the tty needs the hvcs_struct pointer after a hangup */
1266	tty->driver_data = NULL;
1267	hvcsd->port.tty = NULL;
1268
1269	hvcsd->port.count = 0;
1270
1271	/* This will drop any buffered data on the floor which is OK in a hangup
1272	 * scenario. */
1273	memset(&hvcsd->buffer[0], 0x00, HVCS_BUFF_LEN);
1274	hvcsd->chars_in_buffer = 0;
1275
1276	irq = hvcsd->vdev->irq;
1277
1278	spin_unlock_irqrestore(&hvcsd->lock, flags);
1279
1280	free_irq(irq, hvcsd);
1281
1282	/*
1283	 * We need to kref_put() for every open_count we have since the
1284	 * tty_hangup() function doesn't invoke a close per open connection on a
1285	 * non-console device.
1286	 */
1287	while(temp_open_count) {
1288		--temp_open_count;
1289		/*
1290		 * The final put will trigger destruction of the hvcs_struct.
1291		 * NOTE:  If this hangup was signaled from user space then the
1292		 * final put will never happen.
1293		 */
1294		tty_port_put(&hvcsd->port);
1295	}
1296}
1297
1298/*
1299 * NOTE: This is almost always from_user since user level apps interact with the
1300 * /dev nodes. I'm trusting that if hvcs_write gets called and interrupted by
1301 * hvcs_remove (which removes the target device and executes tty_hangup()) that
1302 * tty_hangup will allow hvcs_write time to complete execution before it
1303 * terminates our device.
1304 */
1305static int hvcs_write(struct tty_struct *tty,
1306		const unsigned char *buf, int count)
1307{
1308	struct hvcs_struct *hvcsd = tty->driver_data;
1309	unsigned int unit_address;
1310	const unsigned char *charbuf;
1311	unsigned long flags;
1312	int total_sent = 0;
1313	int tosend = 0;
1314	int result = 0;
1315
1316	/*
1317	 * If they don't check the return code off of their open they may
1318	 * attempt this even if there is no connected device.
1319	 */
1320	if (!hvcsd)
1321		return -ENODEV;
1322
1323	/* Reasonable size to prevent user level flooding */
1324	if (count > HVCS_MAX_FROM_USER) {
1325		printk(KERN_WARNING "HVCS write: count being truncated to"
1326				" HVCS_MAX_FROM_USER.\n");
1327		count = HVCS_MAX_FROM_USER;
1328	}
1329
1330	charbuf = buf;
1331
1332	spin_lock_irqsave(&hvcsd->lock, flags);
1333
1334	/*
1335	 * Somehow an open succeeded but the device was removed or the
1336	 * connection terminated between the vty-server and partner vty during
1337	 * the middle of a write operation?  This is a crummy place to do this
1338	 * but we want to keep it all in the spinlock.
1339	 */
1340	if (hvcsd->port.count <= 0) {
1341		spin_unlock_irqrestore(&hvcsd->lock, flags);
1342		return -ENODEV;
1343	}
1344
1345	unit_address = hvcsd->vdev->unit_address;
1346
1347	while (count > 0) {
1348		tosend = min(count, (HVCS_BUFF_LEN - hvcsd->chars_in_buffer));
1349		/*
1350		 * No more space, this probably means that the last call to
1351		 * hvcs_write() didn't succeed and the buffer was filled up.
1352		 */
1353		if (!tosend)
1354			break;
1355
1356		memcpy(&hvcsd->buffer[hvcsd->chars_in_buffer],
1357				&charbuf[total_sent],
1358				tosend);
1359
1360		hvcsd->chars_in_buffer += tosend;
1361
1362		result = 0;
1363
1364		/*
1365		 * If this is true then we don't want to try writing to the
1366		 * hypervisor because that is the kernel_threads job now.  We'll
1367		 * just add to the buffer.
1368		 */
1369		if (!(hvcsd->todo_mask & HVCS_TRY_WRITE))
1370			/* won't send partial writes */
1371			result = hvc_put_chars(unit_address,
1372					&hvcsd->buffer[0],
1373					hvcsd->chars_in_buffer);
1374
1375		/*
1376		 * Since we know we have enough room in hvcsd->buffer for
1377		 * tosend we record that it was sent regardless of whether the
1378		 * hypervisor actually took it because we have it buffered.
1379		 */
1380		total_sent+=tosend;
1381		count-=tosend;
1382		if (result == 0) {
1383			hvcsd->todo_mask |= HVCS_TRY_WRITE;
1384			hvcs_kick();
1385			break;
1386		}
1387
1388		hvcsd->chars_in_buffer = 0;
1389		/*
1390		 * Test after the chars_in_buffer reset otherwise this could
1391		 * deadlock our writes if hvc_put_chars fails.
1392		 */
1393		if (result < 0)
1394			break;
1395	}
1396
1397	spin_unlock_irqrestore(&hvcsd->lock, flags);
1398
1399	if (result == -1)
1400		return -EIO;
1401	else
1402		return total_sent;
1403}
1404
1405/*
1406 * This is really asking how much can we guarantee that we can send or that we
1407 * absolutely WILL BUFFER if we can't send it.  This driver MUST honor the
1408 * return value, hence the reason for hvcs_struct buffering.
1409 */
1410static int hvcs_write_room(struct tty_struct *tty)
1411{
1412	struct hvcs_struct *hvcsd = tty->driver_data;
1413
1414	if (!hvcsd || hvcsd->port.count <= 0)
1415		return 0;
1416
1417	return HVCS_BUFF_LEN - hvcsd->chars_in_buffer;
1418}
1419
1420static int hvcs_chars_in_buffer(struct tty_struct *tty)
1421{
1422	struct hvcs_struct *hvcsd = tty->driver_data;
1423
1424	return hvcsd->chars_in_buffer;
1425}
1426
1427static const struct tty_operations hvcs_ops = {
1428	.install = hvcs_install,
1429	.open = hvcs_open,
1430	.close = hvcs_close,
1431	.cleanup = hvcs_cleanup,
1432	.hangup = hvcs_hangup,
1433	.write = hvcs_write,
1434	.write_room = hvcs_write_room,
1435	.chars_in_buffer = hvcs_chars_in_buffer,
1436	.unthrottle = hvcs_unthrottle,
1437	.throttle = hvcs_throttle,
1438};
1439
1440static int hvcs_alloc_index_list(int n)
1441{
1442	int i;
1443
1444	hvcs_index_list = kmalloc_array(n, sizeof(hvcs_index_count),
1445					GFP_KERNEL);
1446	if (!hvcs_index_list)
1447		return -ENOMEM;
1448	hvcs_index_count = n;
1449	for (i = 0; i < hvcs_index_count; i++)
1450		hvcs_index_list[i] = -1;
1451	return 0;
1452}
1453
1454static void hvcs_free_index_list(void)
1455{
1456	/* Paranoia check to be thorough. */
1457	kfree(hvcs_index_list);
1458	hvcs_index_list = NULL;
1459	hvcs_index_count = 0;
1460}
1461
1462static int hvcs_initialize(void)
1463{
1464	int rc, num_ttys_to_alloc;
1465
1466	mutex_lock(&hvcs_init_mutex);
1467	if (hvcs_task) {
1468		mutex_unlock(&hvcs_init_mutex);
1469		return 0;
1470	}
1471
1472	/* Has the user specified an overload with an insmod param? */
1473	if (hvcs_parm_num_devs <= 0 ||
1474		(hvcs_parm_num_devs > HVCS_MAX_SERVER_ADAPTERS)) {
1475		num_ttys_to_alloc = HVCS_DEFAULT_SERVER_ADAPTERS;
1476	} else
1477		num_ttys_to_alloc = hvcs_parm_num_devs;
1478
1479	hvcs_tty_driver = alloc_tty_driver(num_ttys_to_alloc);
1480	if (!hvcs_tty_driver) {
1481		mutex_unlock(&hvcs_init_mutex);
1482		return -ENOMEM;
1483	}
1484
1485	if (hvcs_alloc_index_list(num_ttys_to_alloc)) {
1486		rc = -ENOMEM;
1487		goto index_fail;
1488	}
1489
1490	hvcs_tty_driver->driver_name = hvcs_driver_name;
1491	hvcs_tty_driver->name = hvcs_device_node;
1492
1493	/*
1494	 * We'll let the system assign us a major number, indicated by leaving
1495	 * it blank.
1496	 */
1497
1498	hvcs_tty_driver->minor_start = HVCS_MINOR_START;
1499	hvcs_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
1500
1501	/*
1502	 * We role our own so that we DONT ECHO.  We can't echo because the
1503	 * device we are connecting to already echoes by default and this would
1504	 * throw us into a horrible recursive echo-echo-echo loop.
1505	 */
1506	hvcs_tty_driver->init_termios = hvcs_tty_termios;
1507	hvcs_tty_driver->flags = TTY_DRIVER_REAL_RAW;
1508
1509	tty_set_operations(hvcs_tty_driver, &hvcs_ops);
1510
1511	/*
1512	 * The following call will result in sysfs entries that denote the
1513	 * dynamically assigned major and minor numbers for our devices.
1514	 */
1515	if (tty_register_driver(hvcs_tty_driver)) {
1516		printk(KERN_ERR "HVCS: registration as a tty driver failed.\n");
1517		rc = -EIO;
1518		goto register_fail;
1519	}
1520
1521	hvcs_pi_buff = (unsigned long *) __get_free_page(GFP_KERNEL);
1522	if (!hvcs_pi_buff) {
1523		rc = -ENOMEM;
1524		goto buff_alloc_fail;
1525	}
1526
1527	hvcs_task = kthread_run(khvcsd, NULL, "khvcsd");
1528	if (IS_ERR(hvcs_task)) {
1529		printk(KERN_ERR "HVCS: khvcsd creation failed.\n");
1530		rc = -EIO;
1531		goto kthread_fail;
1532	}
1533	mutex_unlock(&hvcs_init_mutex);
1534	return 0;
1535
1536kthread_fail:
1537	free_page((unsigned long)hvcs_pi_buff);
1538buff_alloc_fail:
1539	tty_unregister_driver(hvcs_tty_driver);
1540register_fail:
1541	hvcs_free_index_list();
1542index_fail:
1543	put_tty_driver(hvcs_tty_driver);
1544	hvcs_tty_driver = NULL;
1545	mutex_unlock(&hvcs_init_mutex);
1546	return rc;
1547}
1548
1549static int __init hvcs_module_init(void)
1550{
1551	int rc = vio_register_driver(&hvcs_vio_driver);
1552	if (rc) {
1553		printk(KERN_ERR "HVCS: can't register vio driver\n");
1554		return rc;
1555	}
1556
1557	pr_info("HVCS: Driver registered.\n");
1558
1559	/* This needs to be done AFTER the vio_register_driver() call or else
1560	 * the kobjects won't be initialized properly.
1561	 */
1562	rc = driver_create_file(&(hvcs_vio_driver.driver), &driver_attr_rescan);
1563	if (rc)
1564		pr_warn("HVCS: Failed to create rescan file (err %d)\n", rc);
1565
1566	return 0;
1567}
1568
1569static void __exit hvcs_module_exit(void)
1570{
1571	/*
1572	 * This driver receives hvcs_remove callbacks for each device upon
1573	 * module removal.
1574	 */
1575	vio_unregister_driver(&hvcs_vio_driver);
1576	if (!hvcs_task)
1577		return;
1578
1579	/*
1580	 * This synchronous operation  will wake the khvcsd kthread if it is
1581	 * asleep and will return when khvcsd has terminated.
1582	 */
1583	kthread_stop(hvcs_task);
1584
1585	spin_lock(&hvcs_pi_lock);
1586	free_page((unsigned long)hvcs_pi_buff);
1587	hvcs_pi_buff = NULL;
1588	spin_unlock(&hvcs_pi_lock);
1589
1590	driver_remove_file(&hvcs_vio_driver.driver, &driver_attr_rescan);
1591
1592	tty_unregister_driver(hvcs_tty_driver);
1593
1594	hvcs_free_index_list();
1595
1596	put_tty_driver(hvcs_tty_driver);
1597
1598	printk(KERN_INFO "HVCS: driver module removed.\n");
1599}
1600
1601module_init(hvcs_module_init);
1602module_exit(hvcs_module_exit);