1// SPDX-License-Identifier: GPL-2.0+
   2/*
   3 * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
   4 * Copyright (C) 2001 Paul Mackerras <paulus@au.ibm.com>, IBM
   5 * Copyright (C) 2004 Benjamin Herrenschmidt <benh@kernel.crashing.org>, IBM Corp.
   6 * Copyright (C) 2004 IBM Corporation
   7 *
   8 * Additional Author(s):
   9 *  Ryan S. Arnold <rsa@us.ibm.com>
  10 */
  11
  12#include <linux/console.h>
  13#include <linux/cpumask.h>
  14#include <linux/init.h>
  15#include <linux/kbd_kern.h>
  16#include <linux/kernel.h>
  17#include <linux/kthread.h>
  18#include <linux/list.h>
  19#include <linux/major.h>
  20#include <linux/atomic.h>
  21#include <linux/sysrq.h>
  22#include <linux/tty.h>
  23#include <linux/tty_flip.h>
  24#include <linux/sched.h>
  25#include <linux/spinlock.h>
  26#include <linux/delay.h>
  27#include <linux/freezer.h>
  28#include <linux/slab.h>
  29#include <linux/serial_core.h>
  30
  31#include <linux/uaccess.h>
  32
  33#include "hvc_console.h"
  34
  35#define HVC_MAJOR	229
  36#define HVC_MINOR	0
  37
  38/*
  39 * Wait this long per iteration while trying to push buffered data to the
  40 * hypervisor before allowing the tty to complete a close operation.
  41 */
  42#define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */
  43
  44/*
  45 * These sizes are most efficient for vio, because they are the
  46 * native transfer size. We could make them selectable in the
  47 * future to better deal with backends that want other buffer sizes.
  48 */
  49#define N_OUTBUF	16
  50#define N_INBUF		16
  51
  52#define __ALIGNED__ __attribute__((__aligned__(L1_CACHE_BYTES)))
  53
  54static struct tty_driver *hvc_driver;
  55static struct task_struct *hvc_task;
  56
  57/* Picks up late kicks after list walk but before schedule() */
  58static int hvc_kicked;
  59
  60/* hvc_init is triggered from hvc_alloc, i.e. only when actually used */
  61static atomic_t hvc_needs_init __read_mostly = ATOMIC_INIT(-1);
  62
  63static int hvc_init(void);
  64
  65#ifdef CONFIG_MAGIC_SYSRQ
  66static int sysrq_pressed;
  67#endif
  68
  69/* dynamic list of hvc_struct instances */
  70static LIST_HEAD(hvc_structs);
  71
  72/*
  73 * Protect the list of hvc_struct instances from inserts and removals during
  74 * list traversal.
  75 */
  76static DEFINE_MUTEX(hvc_structs_mutex);
  77
  78/*
  79 * This value is used to assign a tty->index value to a hvc_struct based
  80 * upon order of exposure via hvc_probe(), when we can not match it to
  81 * a console candidate registered with hvc_instantiate().
  82 */
  83static int last_hvc = -1;
  84
  85/*
  86 * Do not call this function with either the hvc_structs_mutex or the hvc_struct
  87 * lock held.  If successful, this function increments the kref reference
  88 * count against the target hvc_struct so it should be released when finished.
  89 */
  90static struct hvc_struct *hvc_get_by_index(int index)
  91{
  92	struct hvc_struct *hp;
  93	unsigned long flags;
  94
  95	mutex_lock(&hvc_structs_mutex);
  96
  97	list_for_each_entry(hp, &hvc_structs, next) {
  98		spin_lock_irqsave(&hp->lock, flags);
  99		if (hp->index == index) {
 100			tty_port_get(&hp->port);
 101			spin_unlock_irqrestore(&hp->lock, flags);
 102			mutex_unlock(&hvc_structs_mutex);
 103			return hp;
 104		}
 105		spin_unlock_irqrestore(&hp->lock, flags);
 106	}
 107	hp = NULL;
 108	mutex_unlock(&hvc_structs_mutex);
 109
 110	return hp;
 111}
 112
 113static int __hvc_flush(const struct hv_ops *ops, uint32_t vtermno, bool wait)
 114{
 115	if (wait)
 116		might_sleep();
 117
 118	if (ops->flush)
 119		return ops->flush(vtermno, wait);
 120	return 0;
 121}
 122
 123static int hvc_console_flush(const struct hv_ops *ops, uint32_t vtermno)
 124{
 125	return __hvc_flush(ops, vtermno, false);
 126}
 127
 128/*
 129 * Wait for the console to flush before writing more to it. This sleeps.
 130 */
 131static int hvc_flush(struct hvc_struct *hp)
 132{
 133	return __hvc_flush(hp->ops, hp->vtermno, true);
 134}
 135
 136/*
 137 * Initial console vtermnos for console API usage prior to full console
 138 * initialization.  Any vty adapter outside this range will not have usable
 139 * console interfaces but can still be used as a tty device.  This has to be
 140 * static because kmalloc will not work during early console init.
 141 */
 142static const struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES];
 143static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
 144	{[0 ... MAX_NR_HVC_CONSOLES - 1] = -1};
 145
 146/*
 147 * Console APIs, NOT TTY.  These APIs are available immediately when
 148 * hvc_console_setup() finds adapters.
 149 */
 150
 151static void hvc_console_print(struct console *co, const char *b,
 152			      unsigned count)
 153{
 154	char c[N_OUTBUF] __ALIGNED__;
 155	unsigned i = 0, n = 0;
 156	int r, donecr = 0, index = co->index;
 157
 158	/* Console access attempt outside of acceptable console range. */
 159	if (index >= MAX_NR_HVC_CONSOLES)
 160		return;
 161
 162	/* This console adapter was removed so it is not usable. */
 163	if (vtermnos[index] == -1)
 164		return;
 165
 166	while (count > 0 || i > 0) {
 167		if (count > 0 && i < sizeof(c)) {
 168			if (b[n] == '\n' && !donecr) {
 169				c[i++] = '\r';
 170				donecr = 1;
 171			} else {
 172				c[i++] = b[n++];
 173				donecr = 0;
 174				--count;
 175			}
 176		} else {
 177			r = cons_ops[index]->put_chars(vtermnos[index], c, i);
 178			if (r <= 0) {
 179				/* throw away characters on error
 180				 * but spin in case of -EAGAIN */
 181				if (r != -EAGAIN) {
 182					i = 0;
 183				} else {
 184					hvc_console_flush(cons_ops[index],
 185						      vtermnos[index]);
 186				}
 187			} else if (r > 0) {
 188				i -= r;
 189				if (i > 0)
 190					memmove(c, c+r, i);
 191			}
 192		}
 193	}
 194	hvc_console_flush(cons_ops[index], vtermnos[index]);
 195}
 196
 197static struct tty_driver *hvc_console_device(struct console *c, int *index)
 198{
 199	if (vtermnos[c->index] == -1)
 200		return NULL;
 201
 202	*index = c->index;
 203	return hvc_driver;
 204}
 205
 206static int hvc_console_setup(struct console *co, char *options)
 207{	
 208	if (co->index < 0 || co->index >= MAX_NR_HVC_CONSOLES)
 209		return -ENODEV;
 210
 211	if (vtermnos[co->index] == -1)
 212		return -ENODEV;
 213
 214	return 0;
 215}
 216
 217static struct console hvc_console = {
 218	.name		= "hvc",
 219	.write		= hvc_console_print,
 220	.device		= hvc_console_device,
 221	.setup		= hvc_console_setup,
 222	.flags		= CON_PRINTBUFFER,
 223	.index		= -1,
 224};
 225
 226/*
 227 * Early console initialization.  Precedes driver initialization.
 228 *
 229 * (1) we are first, and the user specified another driver
 230 * -- index will remain -1
 231 * (2) we are first and the user specified no driver
 232 * -- index will be set to 0, then we will fail setup.
 233 * (3)  we are first and the user specified our driver
 234 * -- index will be set to user specified driver, and we will fail
 235 * (4) we are after driver, and this initcall will register us
 236 * -- if the user didn't specify a driver then the console will match
 237 *
 238 * Note that for cases 2 and 3, we will match later when the io driver
 239 * calls hvc_instantiate() and call register again.
 240 */
 241static int __init hvc_console_init(void)
 242{
 243	register_console(&hvc_console);
 244	return 0;
 245}
 246console_initcall(hvc_console_init);
 247
 248/* callback when the kboject ref count reaches zero. */
 249static void hvc_port_destruct(struct tty_port *port)
 250{
 251	struct hvc_struct *hp = container_of(port, struct hvc_struct, port);
 252	unsigned long flags;
 253
 254	mutex_lock(&hvc_structs_mutex);
 255
 256	spin_lock_irqsave(&hp->lock, flags);
 257	list_del(&(hp->next));
 258	spin_unlock_irqrestore(&hp->lock, flags);
 259
 260	mutex_unlock(&hvc_structs_mutex);
 261
 262	kfree(hp);
 263}
 264
 265static void hvc_check_console(int index)
 266{
 267	/* Already registered, bail out */
 268	if (console_is_registered(&hvc_console))
 269		return;
 270
 271 	/* If this index is what the user requested, then register
 272	 * now (setup won't fail at this point).  It's ok to just
 273	 * call register again if previously .setup failed.
 274	 */
 275	if (index == hvc_console.index)
 276		register_console(&hvc_console);
 277}
 278
 279/*
 280 * hvc_instantiate() is an early console discovery method which locates
 281 * consoles * prior to the vio subsystem discovering them.  Hotplugged
 282 * vty adapters do NOT get an hvc_instantiate() callback since they
 283 * appear after early console init.
 284 */
 285int hvc_instantiate(uint32_t vtermno, int index, const struct hv_ops *ops)
 286{
 287	struct hvc_struct *hp;
 288
 289	if (index < 0 || index >= MAX_NR_HVC_CONSOLES)
 290		return -1;
 291
 292	if (vtermnos[index] != -1)
 293		return -1;
 294
 295	/* make sure no tty has been registered in this index */
 296	hp = hvc_get_by_index(index);
 297	if (hp) {
 298		tty_port_put(&hp->port);
 299		return -1;
 300	}
 301
 302	vtermnos[index] = vtermno;
 303	cons_ops[index] = ops;
 304
 305	/* check if we need to re-register the kernel console */
 306	hvc_check_console(index);
 307
 308	return 0;
 309}
 310EXPORT_SYMBOL_GPL(hvc_instantiate);
 311
 312/* Wake the sleeping khvcd */
 313void hvc_kick(void)
 314{
 315	hvc_kicked = 1;
 316	wake_up_process(hvc_task);
 317}
 318EXPORT_SYMBOL_GPL(hvc_kick);
 319
 320static void hvc_unthrottle(struct tty_struct *tty)
 321{
 322	hvc_kick();
 323}
 324
 325static int hvc_install(struct tty_driver *driver, struct tty_struct *tty)
 326{
 327	struct hvc_struct *hp;
 328	int rc;
 329
 330	/* Auto increments kref reference if found. */
 331	hp = hvc_get_by_index(tty->index);
 332	if (!hp)
 333		return -ENODEV;
 334
 335	tty->driver_data = hp;
 336
 337	rc = tty_port_install(&hp->port, driver, tty);
 338	if (rc)
 339		tty_port_put(&hp->port);
 340	return rc;
 341}
 342
 343/*
 344 * The TTY interface won't be used until after the vio layer has exposed the vty
 345 * adapter to the kernel.
 346 */
 347static int hvc_open(struct tty_struct *tty, struct file * filp)
 348{
 349	struct hvc_struct *hp = tty->driver_data;
 350	unsigned long flags;
 351	int rc = 0;
 352
 353	spin_lock_irqsave(&hp->port.lock, flags);
 354	/* Check and then increment for fast path open. */
 355	if (hp->port.count++ > 0) {
 356		spin_unlock_irqrestore(&hp->port.lock, flags);
 357		hvc_kick();
 358		return 0;
 359	} /* else count == 0 */
 360	spin_unlock_irqrestore(&hp->port.lock, flags);
 361
 362	tty_port_tty_set(&hp->port, tty);
 363
 364	if (hp->ops->notifier_add)
 365		rc = hp->ops->notifier_add(hp, hp->data);
 366
 367	/*
 368	 * If the notifier fails we return an error.  The tty layer
 369	 * will call hvc_close() after a failed open but we don't want to clean
 370	 * up there so we'll clean up here and clear out the previously set
 371	 * tty fields and return the kref reference.
 372	 */
 373	if (rc) {
 374		printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
 375	} else {
 376		/* We are ready... raise DTR/RTS */
 377		if (C_BAUD(tty))
 378			if (hp->ops->dtr_rts)
 379				hp->ops->dtr_rts(hp, true);
 380		tty_port_set_initialized(&hp->port, true);
 381	}
 382
 383	/* Force wakeup of the polling thread */
 384	hvc_kick();
 385
 386	return rc;
 387}
 388
 389static void hvc_close(struct tty_struct *tty, struct file * filp)
 390{
 391	struct hvc_struct *hp = tty->driver_data;
 392	unsigned long flags;
 393
 394	if (tty_hung_up_p(filp))
 395		return;
 396
 397	spin_lock_irqsave(&hp->port.lock, flags);
 398
 399	if (--hp->port.count == 0) {
 400		spin_unlock_irqrestore(&hp->port.lock, flags);
 401		/* We are done with the tty pointer now. */
 402		tty_port_tty_set(&hp->port, NULL);
 403
 404		if (!tty_port_initialized(&hp->port))
 405			return;
 406
 407		if (C_HUPCL(tty))
 408			if (hp->ops->dtr_rts)
 409				hp->ops->dtr_rts(hp, false);
 410
 411		if (hp->ops->notifier_del)
 412			hp->ops->notifier_del(hp, hp->data);
 413
 414		/* cancel pending tty resize work */
 415		cancel_work_sync(&hp->tty_resize);
 416
 417		/*
 418		 * Chain calls chars_in_buffer() and returns immediately if
 419		 * there is no buffered data otherwise sleeps on a wait queue
 420		 * waking periodically to check chars_in_buffer().
 421		 */
 422		tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
 423		tty_port_set_initialized(&hp->port, false);
 424	} else {
 425		if (hp->port.count < 0)
 426			printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
 427				hp->vtermno, hp->port.count);
 428		spin_unlock_irqrestore(&hp->port.lock, flags);
 429	}
 430}
 431
 432static void hvc_cleanup(struct tty_struct *tty)
 433{
 434	struct hvc_struct *hp = tty->driver_data;
 435
 436	tty_port_put(&hp->port);
 437}
 438
 439static void hvc_hangup(struct tty_struct *tty)
 440{
 441	struct hvc_struct *hp = tty->driver_data;
 442	unsigned long flags;
 443
 444	if (!hp)
 445		return;
 446
 447	/* cancel pending tty resize work */
 448	cancel_work_sync(&hp->tty_resize);
 449
 450	spin_lock_irqsave(&hp->port.lock, flags);
 451
 452	/*
 453	 * The N_TTY line discipline has problems such that in a close vs
 454	 * open->hangup case this can be called after the final close so prevent
 455	 * that from happening for now.
 456	 */
 457	if (hp->port.count <= 0) {
 458		spin_unlock_irqrestore(&hp->port.lock, flags);
 459		return;
 460	}
 461
 462	hp->port.count = 0;
 463	spin_unlock_irqrestore(&hp->port.lock, flags);
 464	tty_port_tty_set(&hp->port, NULL);
 465
 466	hp->n_outbuf = 0;
 467
 468	if (hp->ops->notifier_hangup)
 469		hp->ops->notifier_hangup(hp, hp->data);
 470}
 471
 472/*
 473 * Push buffered characters whether they were just recently buffered or waiting
 474 * on a blocked hypervisor.  Call this function with hp->lock held.
 475 */
 476static int hvc_push(struct hvc_struct *hp)
 477{
 478	int n;
 479
 480	n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
 481	if (n <= 0) {
 482		if (n == 0 || n == -EAGAIN) {
 483			hp->do_wakeup = 1;
 484			return 0;
 485		}
 486		/* throw away output on error; this happens when
 487		   there is no session connected to the vterm. */
 488		hp->n_outbuf = 0;
 489	} else
 490		hp->n_outbuf -= n;
 491	if (hp->n_outbuf > 0)
 492		memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
 493	else
 494		hp->do_wakeup = 1;
 495
 496	return n;
 497}
 498
 499static ssize_t hvc_write(struct tty_struct *tty, const u8 *buf, size_t count)
 500{
 501	struct hvc_struct *hp = tty->driver_data;
 502	unsigned long flags;
 503	size_t rsize, written = 0;
 504
 505	/* This write was probably executed during a tty close. */
 506	if (!hp)
 507		return -EPIPE;
 508
 509	/* FIXME what's this (unprotected) check for? */
 510	if (hp->port.count <= 0)
 511		return -EIO;
 512
 513	while (count > 0) {
 514		int ret = 0;
 515
 516		spin_lock_irqsave(&hp->lock, flags);
 517
 518		rsize = hp->outbuf_size - hp->n_outbuf;
 519
 520		if (rsize) {
 521			if (rsize > count)
 522				rsize = count;
 523			memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
 524			count -= rsize;
 525			buf += rsize;
 526			hp->n_outbuf += rsize;
 527			written += rsize;
 528		}
 529
 530		if (hp->n_outbuf > 0)
 531			ret = hvc_push(hp);
 532
 533		spin_unlock_irqrestore(&hp->lock, flags);
 534
 535		if (!ret)
 536			break;
 537
 538		if (count) {
 539			if (hp->n_outbuf > 0)
 540				hvc_flush(hp);
 541			cond_resched();
 542		}
 543	}
 544
 545	/*
 546	 * Racy, but harmless, kick thread if there is still pending data.
 547	 */
 548	if (hp->n_outbuf)
 549		hvc_kick();
 550
 551	return written;
 552}
 553
 554/**
 555 * hvc_set_winsz() - Resize the hvc tty terminal window.
 556 * @work:	work structure.
 557 *
 558 * The routine shall not be called within an atomic context because it
 559 * might sleep.
 560 *
 561 * Locking:	hp->lock
 562 */
 563static void hvc_set_winsz(struct work_struct *work)
 564{
 565	struct hvc_struct *hp;
 566	unsigned long hvc_flags;
 567	struct tty_struct *tty;
 568	struct winsize ws;
 569
 570	hp = container_of(work, struct hvc_struct, tty_resize);
 571
 572	tty = tty_port_tty_get(&hp->port);
 573	if (!tty)
 574		return;
 575
 576	spin_lock_irqsave(&hp->lock, hvc_flags);
 577	ws = hp->ws;
 578	spin_unlock_irqrestore(&hp->lock, hvc_flags);
 579
 580	tty_do_resize(tty, &ws);
 581	tty_kref_put(tty);
 582}
 583
 584/*
 585 * This is actually a contract between the driver and the tty layer outlining
 586 * how much write room the driver can guarantee will be sent OR BUFFERED.  This
 587 * driver MUST honor the return value.
 588 */
 589static unsigned int hvc_write_room(struct tty_struct *tty)
 590{
 591	struct hvc_struct *hp = tty->driver_data;
 592
 593	if (!hp)
 594		return 0;
 595
 596	return hp->outbuf_size - hp->n_outbuf;
 597}
 598
 599static unsigned int hvc_chars_in_buffer(struct tty_struct *tty)
 600{
 601	struct hvc_struct *hp = tty->driver_data;
 602
 603	if (!hp)
 604		return 0;
 605	return hp->n_outbuf;
 606}
 607
 608/*
 609 * timeout will vary between the MIN and MAX values defined here.  By default
 610 * and during console activity we will use a default MIN_TIMEOUT of 10.  When
 611 * the console is idle, we increase the timeout value on each pass through
 612 * msleep until we reach the max.  This may be noticeable as a brief (average
 613 * one second) delay on the console before the console responds to input when
 614 * there has been no input for some time.
 615 */
 616#define MIN_TIMEOUT		(10)
 617#define MAX_TIMEOUT		(2000)
 618static u32 timeout = MIN_TIMEOUT;
 619
 620/*
 621 * Maximum number of bytes to get from the console driver if hvc_poll is
 622 * called from driver (and can't sleep). Any more than this and we break
 623 * and start polling with khvcd. This value was derived from an OpenBMC
 624 * console with the OPAL driver that results in about 0.25ms interrupts off
 625 * latency.
 626 */
 627#define HVC_ATOMIC_READ_MAX	128
 628
 629#define HVC_POLL_READ	0x00000001
 630#define HVC_POLL_WRITE	0x00000002
 631
 632static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
 633{
 634	struct tty_struct *tty;
 635	int i, n, count, poll_mask = 0;
 636	char buf[N_INBUF] __ALIGNED__;
 637	unsigned long flags;
 638	int read_total = 0;
 639	int written_total = 0;
 640
 641	spin_lock_irqsave(&hp->lock, flags);
 642
 643	/* Push pending writes */
 644	if (hp->n_outbuf > 0)
 645		written_total = hvc_push(hp);
 646
 647	/* Reschedule us if still some write pending */
 648	if (hp->n_outbuf > 0) {
 649		poll_mask |= HVC_POLL_WRITE;
 650		/* If hvc_push() was not able to write, sleep a few msecs */
 651		timeout = (written_total) ? 0 : MIN_TIMEOUT;
 652	}
 653
 654	if (may_sleep) {
 655		spin_unlock_irqrestore(&hp->lock, flags);
 656		cond_resched();
 657		spin_lock_irqsave(&hp->lock, flags);
 658	}
 659
 660	/* No tty attached, just skip */
 661	tty = tty_port_tty_get(&hp->port);
 662	if (tty == NULL)
 663		goto bail;
 664
 665	/* Now check if we can get data (are we throttled ?) */
 666	if (tty_throttled(tty))
 667		goto out;
 668
 669	/* If we aren't notifier driven and aren't throttled, we always
 670	 * request a reschedule
 671	 */
 672	if (!hp->irq_requested)
 673		poll_mask |= HVC_POLL_READ;
 674
 675 read_again:
 676	/* Read data if any */
 677	count = tty_buffer_request_room(&hp->port, N_INBUF);
 678
 679	/* If flip is full, just reschedule a later read */
 680	if (count == 0) {
 681		poll_mask |= HVC_POLL_READ;
 682		goto out;
 683	}
 684
 685	n = hp->ops->get_chars(hp->vtermno, buf, count);
 686	if (n <= 0) {
 687		/* Hangup the tty when disconnected from host */
 688		if (n == -EPIPE) {
 689			spin_unlock_irqrestore(&hp->lock, flags);
 690			tty_hangup(tty);
 691			spin_lock_irqsave(&hp->lock, flags);
 692		} else if ( n == -EAGAIN ) {
 693			/*
 694			 * Some back-ends can only ensure a certain min
 695			 * num of bytes read, which may be > 'count'.
 696			 * Let the tty clear the flip buff to make room.
 697			 */
 698			poll_mask |= HVC_POLL_READ;
 699		}
 700		goto out;
 701	}
 702
 703	for (i = 0; i < n; ++i) {
 704#ifdef CONFIG_MAGIC_SYSRQ
 705		if (hp->index == hvc_console.index) {
 706			/* Handle the SysRq Hack */
 707			/* XXX should support a sequence */
 708			if (buf[i] == '\x0f') {	/* ^O */
 709				/* if ^O is pressed again, reset
 710				 * sysrq_pressed and flip ^O char */
 711				sysrq_pressed = !sysrq_pressed;
 712				if (sysrq_pressed)
 713					continue;
 714			} else if (sysrq_pressed) {
 715				handle_sysrq(buf[i]);
 716				sysrq_pressed = 0;
 717				continue;
 718			}
 719		}
 720#endif /* CONFIG_MAGIC_SYSRQ */
 721		tty_insert_flip_char(&hp->port, buf[i], 0);
 722	}
 723	read_total += n;
 724
 725	if (may_sleep) {
 726		/* Keep going until the flip is full */
 727		spin_unlock_irqrestore(&hp->lock, flags);
 728		cond_resched();
 729		spin_lock_irqsave(&hp->lock, flags);
 730		goto read_again;
 731	} else if (read_total < HVC_ATOMIC_READ_MAX) {
 732		/* Break and defer if it's a large read in atomic */
 733		goto read_again;
 734	}
 735
 736	/*
 737	 * Latency break, schedule another poll immediately.
 738	 */
 739	poll_mask |= HVC_POLL_READ;
 740
 741 out:
 742	/* Wakeup write queue if necessary */
 743	if (hp->do_wakeup) {
 744		hp->do_wakeup = 0;
 745		tty_wakeup(tty);
 746	}
 747 bail:
 748	spin_unlock_irqrestore(&hp->lock, flags);
 749
 750	if (read_total) {
 751		/* Activity is occurring, so reset the polling backoff value to
 752		   a minimum for performance. */
 753		timeout = MIN_TIMEOUT;
 754
 755		tty_flip_buffer_push(&hp->port);
 756	}
 757	tty_kref_put(tty);
 758
 759	return poll_mask;
 760}
 761
 762int hvc_poll(struct hvc_struct *hp)
 763{
 764	return __hvc_poll(hp, false);
 765}
 766EXPORT_SYMBOL_GPL(hvc_poll);
 767
 768/**
 769 * __hvc_resize() - Update terminal window size information.
 770 * @hp:		HVC console pointer
 771 * @ws:		Terminal window size structure
 772 *
 773 * Stores the specified window size information in the hvc structure of @hp.
 774 * The function schedule the tty resize update.
 775 *
 776 * Locking:	Locking free; the function MUST be called holding hp->lock
 777 */
 778void __hvc_resize(struct hvc_struct *hp, struct winsize ws)
 779{
 780	hp->ws = ws;
 781	schedule_work(&hp->tty_resize);
 782}
 783EXPORT_SYMBOL_GPL(__hvc_resize);
 784
 785/*
 786 * This kthread is either polling or interrupt driven.  This is determined by
 787 * calling hvc_poll() who determines whether a console adapter support
 788 * interrupts.
 789 */
 790static int khvcd(void *unused)
 791{
 792	int poll_mask;
 793	struct hvc_struct *hp;
 794
 795	set_freezable();
 796	do {
 797		poll_mask = 0;
 798		hvc_kicked = 0;
 799		try_to_freeze();
 800		wmb();
 801		if (!cpus_are_in_xmon()) {
 802			mutex_lock(&hvc_structs_mutex);
 803			list_for_each_entry(hp, &hvc_structs, next) {
 804				poll_mask |= __hvc_poll(hp, true);
 805				cond_resched();
 806			}
 807			mutex_unlock(&hvc_structs_mutex);
 808		} else
 809			poll_mask |= HVC_POLL_READ;
 810		if (hvc_kicked)
 811			continue;
 812		set_current_state(TASK_INTERRUPTIBLE);
 813		if (!hvc_kicked) {
 814			if (poll_mask == 0)
 815				schedule();
 816			else {
 817				unsigned long j_timeout;
 818
 819				if (timeout < MAX_TIMEOUT)
 820					timeout += (timeout >> 6) + 1;
 821
 822				/*
 823				 * We don't use msleep_interruptible otherwise
 824				 * "kick" will fail to wake us up
 825				 */
 826				j_timeout = msecs_to_jiffies(timeout) + 1;
 827				schedule_timeout_interruptible(j_timeout);
 828			}
 829		}
 830		__set_current_state(TASK_RUNNING);
 831	} while (!kthread_should_stop());
 832
 833	return 0;
 834}
 835
 836static int hvc_tiocmget(struct tty_struct *tty)
 837{
 838	struct hvc_struct *hp = tty->driver_data;
 839
 840	if (!hp || !hp->ops->tiocmget)
 841		return -EINVAL;
 842	return hp->ops->tiocmget(hp);
 843}
 844
 845static int hvc_tiocmset(struct tty_struct *tty,
 846			unsigned int set, unsigned int clear)
 847{
 848	struct hvc_struct *hp = tty->driver_data;
 849
 850	if (!hp || !hp->ops->tiocmset)
 851		return -EINVAL;
 852	return hp->ops->tiocmset(hp, set, clear);
 853}
 854
 855#ifdef CONFIG_CONSOLE_POLL
 856static int hvc_poll_init(struct tty_driver *driver, int line, char *options)
 857{
 858	return 0;
 859}
 860
 861static int hvc_poll_get_char(struct tty_driver *driver, int line)
 862{
 863	struct tty_struct *tty = driver->ttys[0];
 864	struct hvc_struct *hp = tty->driver_data;
 865	int n;
 866	char ch;
 867
 868	n = hp->ops->get_chars(hp->vtermno, &ch, 1);
 869
 870	if (n <= 0)
 871		return NO_POLL_CHAR;
 872
 873	return ch;
 874}
 875
 876static void hvc_poll_put_char(struct tty_driver *driver, int line, char ch)
 877{
 878	struct tty_struct *tty = driver->ttys[0];
 879	struct hvc_struct *hp = tty->driver_data;
 880	int n;
 881
 882	do {
 883		n = hp->ops->put_chars(hp->vtermno, &ch, 1);
 884	} while (n <= 0);
 885}
 886#endif
 887
 888static const struct tty_operations hvc_ops = {
 889	.install = hvc_install,
 890	.open = hvc_open,
 891	.close = hvc_close,
 892	.cleanup = hvc_cleanup,
 893	.write = hvc_write,
 894	.hangup = hvc_hangup,
 895	.unthrottle = hvc_unthrottle,
 896	.write_room = hvc_write_room,
 897	.chars_in_buffer = hvc_chars_in_buffer,
 898	.tiocmget = hvc_tiocmget,
 899	.tiocmset = hvc_tiocmset,
 900#ifdef CONFIG_CONSOLE_POLL
 901	.poll_init = hvc_poll_init,
 902	.poll_get_char = hvc_poll_get_char,
 903	.poll_put_char = hvc_poll_put_char,
 904#endif
 905};
 906
 907static const struct tty_port_operations hvc_port_ops = {
 908	.destruct = hvc_port_destruct,
 909};
 910
 911struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
 912			     const struct hv_ops *ops,
 913			     int outbuf_size)
 914{
 915	struct hvc_struct *hp;
 916	int i;
 917
 918	/* We wait until a driver actually comes along */
 919	if (atomic_inc_not_zero(&hvc_needs_init)) {
 920		int err = hvc_init();
 921		if (err)
 922			return ERR_PTR(err);
 923	}
 924
 925	hp = kzalloc(struct_size(hp, outbuf, outbuf_size), GFP_KERNEL);
 
 926	if (!hp)
 927		return ERR_PTR(-ENOMEM);
 928
 929	hp->vtermno = vtermno;
 930	hp->data = data;
 931	hp->ops = ops;
 932	hp->outbuf_size = outbuf_size;
 
 933
 934	tty_port_init(&hp->port);
 935	hp->port.ops = &hvc_port_ops;
 936
 937	INIT_WORK(&hp->tty_resize, hvc_set_winsz);
 938	spin_lock_init(&hp->lock);
 939	mutex_lock(&hvc_structs_mutex);
 940
 941	/*
 942	 * find index to use:
 943	 * see if this vterm id matches one registered for console.
 944	 */
 945	for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
 946		if (vtermnos[i] == hp->vtermno &&
 947		    cons_ops[i] == hp->ops)
 948			break;
 949
 950	if (i >= MAX_NR_HVC_CONSOLES) {
 951
 952		/* find 'empty' slot for console */
 953		for (i = 0; i < MAX_NR_HVC_CONSOLES && vtermnos[i] != -1; i++) {
 954		}
 955
 956		/* no matching slot, just use a counter */
 957		if (i == MAX_NR_HVC_CONSOLES)
 958			i = ++last_hvc + MAX_NR_HVC_CONSOLES;
 959	}
 960
 961	hp->index = i;
 962	if (i < MAX_NR_HVC_CONSOLES) {
 963		cons_ops[i] = ops;
 964		vtermnos[i] = vtermno;
 965	}
 966
 967	list_add_tail(&(hp->next), &hvc_structs);
 968	mutex_unlock(&hvc_structs_mutex);
 969
 970	/* check if we need to re-register the kernel console */
 971	hvc_check_console(i);
 972
 973	return hp;
 974}
 975EXPORT_SYMBOL_GPL(hvc_alloc);
 976
 977void hvc_remove(struct hvc_struct *hp)
 978{
 979	unsigned long flags;
 980	struct tty_struct *tty;
 981
 982	tty = tty_port_tty_get(&hp->port);
 983
 984	console_lock();
 985	spin_lock_irqsave(&hp->lock, flags);
 986	if (hp->index < MAX_NR_HVC_CONSOLES) {
 987		vtermnos[hp->index] = -1;
 988		cons_ops[hp->index] = NULL;
 989	}
 990
 991	/* Don't whack hp->irq because tty_hangup() will need to free the irq. */
 992
 993	spin_unlock_irqrestore(&hp->lock, flags);
 994	console_unlock();
 995
 996	/*
 997	 * We 'put' the instance that was grabbed when the kref instance
 998	 * was initialized using kref_init().  Let the last holder of this
 999	 * kref cause it to be removed, which will probably be the tty_vhangup
1000	 * below.
1001	 */
1002	tty_port_put(&hp->port);
1003
1004	/*
1005	 * This function call will auto chain call hvc_hangup.
1006	 */
1007	if (tty) {
1008		tty_vhangup(tty);
1009		tty_kref_put(tty);
1010	}
 
1011}
1012EXPORT_SYMBOL_GPL(hvc_remove);
1013
1014/* Driver initialization: called as soon as someone uses hvc_alloc(). */
1015static int hvc_init(void)
1016{
1017	struct tty_driver *drv;
1018	int err;
1019
1020	/* We need more than hvc_count adapters due to hotplug additions. */
1021	drv = tty_alloc_driver(HVC_ALLOC_TTY_ADAPTERS, TTY_DRIVER_REAL_RAW |
1022			TTY_DRIVER_RESET_TERMIOS);
1023	if (IS_ERR(drv)) {
1024		err = PTR_ERR(drv);
1025		goto out;
1026	}
1027
1028	drv->driver_name = "hvc";
1029	drv->name = "hvc";
1030	drv->major = HVC_MAJOR;
1031	drv->minor_start = HVC_MINOR;
1032	drv->type = TTY_DRIVER_TYPE_SYSTEM;
1033	drv->init_termios = tty_std_termios;
 
1034	tty_set_operations(drv, &hvc_ops);
1035
1036	/* Always start the kthread because there can be hotplug vty adapters
1037	 * added later. */
1038	hvc_task = kthread_run(khvcd, NULL, "khvcd");
1039	if (IS_ERR(hvc_task)) {
1040		printk(KERN_ERR "Couldn't create kthread for console.\n");
1041		err = PTR_ERR(hvc_task);
1042		goto put_tty;
1043	}
1044
1045	err = tty_register_driver(drv);
1046	if (err) {
1047		printk(KERN_ERR "Couldn't register hvc console driver\n");
1048		goto stop_thread;
1049	}
1050
1051	/*
1052	 * Make sure tty is fully registered before allowing it to be
1053	 * found by hvc_console_device.
1054	 */
1055	smp_mb();
1056	hvc_driver = drv;
1057	return 0;
1058
1059stop_thread:
1060	kthread_stop(hvc_task);
1061	hvc_task = NULL;
1062put_tty:
1063	tty_driver_kref_put(drv);
1064out:
1065	return err;
1066}