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__(sizeof(long))))
  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 enabled, bail out */
 268	if (hvc_console.flags & CON_ENABLED)
 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 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	/* reserve all indices up to and including this index */
 306	if (last_hvc < index)
 307		last_hvc = index;
 308
 309	/* check if we need to re-register the kernel console */
 310	hvc_check_console(index);
 311
 312	return 0;
 313}
 314EXPORT_SYMBOL_GPL(hvc_instantiate);
 315
 316/* Wake the sleeping khvcd */
 317void hvc_kick(void)
 318{
 319	hvc_kicked = 1;
 320	wake_up_process(hvc_task);
 321}
 322EXPORT_SYMBOL_GPL(hvc_kick);
 323
 324static void hvc_unthrottle(struct tty_struct *tty)
 325{
 326	hvc_kick();
 327}
 328
 329static int hvc_install(struct tty_driver *driver, struct tty_struct *tty)
 330{
 331	struct hvc_struct *hp;
 332	int rc;
 333
 334	/* Auto increments kref reference if found. */
 335	hp = hvc_get_by_index(tty->index);
 336	if (!hp)
 337		return -ENODEV;
 338
 339	tty->driver_data = hp;
 340
 341	rc = tty_port_install(&hp->port, driver, tty);
 342	if (rc)
 343		tty_port_put(&hp->port);
 344	return rc;
 345}
 346
 347/*
 348 * The TTY interface won't be used until after the vio layer has exposed the vty
 349 * adapter to the kernel.
 350 */
 351static int hvc_open(struct tty_struct *tty, struct file * filp)
 352{
 353	struct hvc_struct *hp = tty->driver_data;
 354	unsigned long flags;
 355	int rc = 0;
 356
 357	spin_lock_irqsave(&hp->port.lock, flags);
 358	/* Check and then increment for fast path open. */
 359	if (hp->port.count++ > 0) {
 360		spin_unlock_irqrestore(&hp->port.lock, flags);
 361		hvc_kick();
 362		return 0;
 363	} /* else count == 0 */
 364	spin_unlock_irqrestore(&hp->port.lock, flags);
 365
 366	tty_port_tty_set(&hp->port, tty);
 367
 368	if (hp->ops->notifier_add)
 369		rc = hp->ops->notifier_add(hp, hp->data);
 370
 371	/*
 372	 * If the notifier fails we return an error.  The tty layer
 373	 * will call hvc_close() after a failed open but we don't want to clean
 374	 * up there so we'll clean up here and clear out the previously set
 375	 * tty fields and return the kref reference.
 376	 */
 377	if (rc) {
 378		tty_port_tty_set(&hp->port, NULL);
 379		tty->driver_data = NULL;
 380		tty_port_put(&hp->port);
 381		printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
 382	} else
 383		/* We are ready... raise DTR/RTS */
 384		if (C_BAUD(tty))
 385			if (hp->ops->dtr_rts)
 386				hp->ops->dtr_rts(hp, 1);
 387
 388	/* Force wakeup of the polling thread */
 389	hvc_kick();
 390
 391	return rc;
 392}
 393
 394static void hvc_close(struct tty_struct *tty, struct file * filp)
 395{
 396	struct hvc_struct *hp;
 397	unsigned long flags;
 398
 399	if (tty_hung_up_p(filp))
 400		return;
 401
 402	/*
 403	 * No driver_data means that this close was issued after a failed
 404	 * hvc_open by the tty layer's release_dev() function and we can just
 405	 * exit cleanly because the kref reference wasn't made.
 406	 */
 407	if (!tty->driver_data)
 408		return;
 409
 410	hp = tty->driver_data;
 411
 412	spin_lock_irqsave(&hp->port.lock, flags);
 413
 414	if (--hp->port.count == 0) {
 415		spin_unlock_irqrestore(&hp->port.lock, flags);
 416		/* We are done with the tty pointer now. */
 417		tty_port_tty_set(&hp->port, NULL);
 418
 419		if (C_HUPCL(tty))
 420			if (hp->ops->dtr_rts)
 421				hp->ops->dtr_rts(hp, 0);
 422
 423		if (hp->ops->notifier_del)
 424			hp->ops->notifier_del(hp, hp->data);
 425
 426		/* cancel pending tty resize work */
 427		cancel_work_sync(&hp->tty_resize);
 428
 429		/*
 430		 * Chain calls chars_in_buffer() and returns immediately if
 431		 * there is no buffered data otherwise sleeps on a wait queue
 432		 * waking periodically to check chars_in_buffer().
 433		 */
 434		tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
 435	} else {
 436		if (hp->port.count < 0)
 437			printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
 438				hp->vtermno, hp->port.count);
 439		spin_unlock_irqrestore(&hp->port.lock, flags);
 440	}
 441}
 442
 443static void hvc_cleanup(struct tty_struct *tty)
 444{
 445	struct hvc_struct *hp = tty->driver_data;
 446
 447	tty_port_put(&hp->port);
 448}
 449
 450static void hvc_hangup(struct tty_struct *tty)
 451{
 452	struct hvc_struct *hp = tty->driver_data;
 453	unsigned long flags;
 454
 455	if (!hp)
 456		return;
 457
 458	/* cancel pending tty resize work */
 459	cancel_work_sync(&hp->tty_resize);
 460
 461	spin_lock_irqsave(&hp->port.lock, flags);
 462
 463	/*
 464	 * The N_TTY line discipline has problems such that in a close vs
 465	 * open->hangup case this can be called after the final close so prevent
 466	 * that from happening for now.
 467	 */
 468	if (hp->port.count <= 0) {
 469		spin_unlock_irqrestore(&hp->port.lock, flags);
 470		return;
 471	}
 472
 473	hp->port.count = 0;
 474	spin_unlock_irqrestore(&hp->port.lock, flags);
 475	tty_port_tty_set(&hp->port, NULL);
 476
 477	hp->n_outbuf = 0;
 478
 479	if (hp->ops->notifier_hangup)
 480		hp->ops->notifier_hangup(hp, hp->data);
 481}
 482
 483/*
 484 * Push buffered characters whether they were just recently buffered or waiting
 485 * on a blocked hypervisor.  Call this function with hp->lock held.
 486 */
 487static int hvc_push(struct hvc_struct *hp)
 488{
 489	int n;
 490
 491	n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
 492	if (n <= 0) {
 493		if (n == 0 || n == -EAGAIN) {
 494			hp->do_wakeup = 1;
 495			return 0;
 496		}
 497		/* throw away output on error; this happens when
 498		   there is no session connected to the vterm. */
 499		hp->n_outbuf = 0;
 500	} else
 501		hp->n_outbuf -= n;
 502	if (hp->n_outbuf > 0)
 503		memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
 504	else
 505		hp->do_wakeup = 1;
 506
 507	return n;
 508}
 509
 510static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count)
 511{
 512	struct hvc_struct *hp = tty->driver_data;
 513	unsigned long flags;
 514	int rsize, written = 0;
 515
 516	/* This write was probably executed during a tty close. */
 517	if (!hp)
 518		return -EPIPE;
 519
 520	/* FIXME what's this (unprotected) check for? */
 521	if (hp->port.count <= 0)
 522		return -EIO;
 523
 524	while (count > 0) {
 525		int ret = 0;
 526
 527		spin_lock_irqsave(&hp->lock, flags);
 528
 529		rsize = hp->outbuf_size - hp->n_outbuf;
 530
 531		if (rsize) {
 532			if (rsize > count)
 533				rsize = count;
 534			memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
 535			count -= rsize;
 536			buf += rsize;
 537			hp->n_outbuf += rsize;
 538			written += rsize;
 539		}
 540
 541		if (hp->n_outbuf > 0)
 542			ret = hvc_push(hp);
 543
 544		spin_unlock_irqrestore(&hp->lock, flags);
 545
 546		if (!ret)
 547			break;
 
 548
 549		if (count) {
 550			if (hp->n_outbuf > 0)
 551				hvc_flush(hp);
 552			cond_resched();
 553		}
 
 
 
 
 554	}
 
 555
 556	/*
 557	 * Racy, but harmless, kick thread if there is still pending data.
 558	 */
 559	if (hp->n_outbuf)
 560		hvc_kick();
 561
 562	return written;
 563}
 564
 565/**
 566 * hvc_set_winsz() - Resize the hvc tty terminal window.
 567 * @work:	work structure.
 568 *
 569 * The routine shall not be called within an atomic context because it
 570 * might sleep.
 571 *
 572 * Locking:	hp->lock
 573 */
 574static void hvc_set_winsz(struct work_struct *work)
 575{
 576	struct hvc_struct *hp;
 577	unsigned long hvc_flags;
 578	struct tty_struct *tty;
 579	struct winsize ws;
 580
 581	hp = container_of(work, struct hvc_struct, tty_resize);
 582
 583	tty = tty_port_tty_get(&hp->port);
 584	if (!tty)
 585		return;
 586
 587	spin_lock_irqsave(&hp->lock, hvc_flags);
 588	ws = hp->ws;
 589	spin_unlock_irqrestore(&hp->lock, hvc_flags);
 590
 591	tty_do_resize(tty, &ws);
 592	tty_kref_put(tty);
 593}
 594
 595/*
 596 * This is actually a contract between the driver and the tty layer outlining
 597 * how much write room the driver can guarantee will be sent OR BUFFERED.  This
 598 * driver MUST honor the return value.
 599 */
 600static int hvc_write_room(struct tty_struct *tty)
 601{
 602	struct hvc_struct *hp = tty->driver_data;
 603
 604	if (!hp)
 605		return 0;
 606
 607	return hp->outbuf_size - hp->n_outbuf;
 608}
 609
 610static int hvc_chars_in_buffer(struct tty_struct *tty)
 611{
 612	struct hvc_struct *hp = tty->driver_data;
 613
 614	if (!hp)
 615		return 0;
 616	return hp->n_outbuf;
 617}
 618
 619/*
 620 * timeout will vary between the MIN and MAX values defined here.  By default
 621 * and during console activity we will use a default MIN_TIMEOUT of 10.  When
 622 * the console is idle, we increase the timeout value on each pass through
 623 * msleep until we reach the max.  This may be noticeable as a brief (average
 624 * one second) delay on the console before the console responds to input when
 625 * there has been no input for some time.
 626 */
 627#define MIN_TIMEOUT		(10)
 628#define MAX_TIMEOUT		(2000)
 629static u32 timeout = MIN_TIMEOUT;
 630
 631/*
 632 * Maximum number of bytes to get from the console driver if hvc_poll is
 633 * called from driver (and can't sleep). Any more than this and we break
 634 * and start polling with khvcd. This value was derived from from an OpenBMC
 635 * console with the OPAL driver that results in about 0.25ms interrupts off
 636 * latency.
 637 */
 638#define HVC_ATOMIC_READ_MAX	128
 639
 640#define HVC_POLL_READ	0x00000001
 641#define HVC_POLL_WRITE	0x00000002
 642
 643static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
 644{
 645	struct tty_struct *tty;
 646	int i, n, count, poll_mask = 0;
 647	char buf[N_INBUF] __ALIGNED__;
 648	unsigned long flags;
 649	int read_total = 0;
 650	int written_total = 0;
 651
 652	spin_lock_irqsave(&hp->lock, flags);
 653
 654	/* Push pending writes */
 655	if (hp->n_outbuf > 0)
 656		written_total = hvc_push(hp);
 657
 658	/* Reschedule us if still some write pending */
 659	if (hp->n_outbuf > 0) {
 660		poll_mask |= HVC_POLL_WRITE;
 661		/* If hvc_push() was not able to write, sleep a few msecs */
 662		timeout = (written_total) ? 0 : MIN_TIMEOUT;
 663	}
 664
 665	if (may_sleep) {
 666		spin_unlock_irqrestore(&hp->lock, flags);
 667		cond_resched();
 668		spin_lock_irqsave(&hp->lock, flags);
 669	}
 670
 671	/* No tty attached, just skip */
 672	tty = tty_port_tty_get(&hp->port);
 673	if (tty == NULL)
 674		goto bail;
 675
 676	/* Now check if we can get data (are we throttled ?) */
 677	if (tty_throttled(tty))
 678		goto out;
 679
 680	/* If we aren't notifier driven and aren't throttled, we always
 681	 * request a reschedule
 682	 */
 683	if (!hp->irq_requested)
 684		poll_mask |= HVC_POLL_READ;
 685
 686 read_again:
 687	/* Read data if any */
 688	count = tty_buffer_request_room(&hp->port, N_INBUF);
 
 689
 690	/* If flip is full, just reschedule a later read */
 691	if (count == 0) {
 692		poll_mask |= HVC_POLL_READ;
 693		goto out;
 694	}
 695
 696	n = hp->ops->get_chars(hp->vtermno, buf, count);
 697	if (n <= 0) {
 698		/* Hangup the tty when disconnected from host */
 699		if (n == -EPIPE) {
 700			spin_unlock_irqrestore(&hp->lock, flags);
 701			tty_hangup(tty);
 702			spin_lock_irqsave(&hp->lock, flags);
 703		} else if ( n == -EAGAIN ) {
 704			/*
 705			 * Some back-ends can only ensure a certain min
 706			 * num of bytes read, which may be > 'count'.
 707			 * Let the tty clear the flip buff to make room.
 708			 */
 709			poll_mask |= HVC_POLL_READ;
 
 710		}
 711		goto out;
 712	}
 713
 714	for (i = 0; i < n; ++i) {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 715#ifdef CONFIG_MAGIC_SYSRQ
 716		if (hp->index == hvc_console.index) {
 717			/* Handle the SysRq Hack */
 718			/* XXX should support a sequence */
 719			if (buf[i] == '\x0f') {	/* ^O */
 720				/* if ^O is pressed again, reset
 721				 * sysrq_pressed and flip ^O char */
 722				sysrq_pressed = !sysrq_pressed;
 723				if (sysrq_pressed)
 
 
 
 
 724					continue;
 725			} else if (sysrq_pressed) {
 726				handle_sysrq(buf[i]);
 727				sysrq_pressed = 0;
 728				continue;
 729			}
 730		}
 731#endif /* CONFIG_MAGIC_SYSRQ */
 732		tty_insert_flip_char(&hp->port, buf[i], 0);
 733	}
 734	read_total += n;
 735
 736	if (may_sleep) {
 737		/* Keep going until the flip is full */
 738		spin_unlock_irqrestore(&hp->lock, flags);
 739		cond_resched();
 740		spin_lock_irqsave(&hp->lock, flags);
 741		goto read_again;
 742	} else if (read_total < HVC_ATOMIC_READ_MAX) {
 743		/* Break and defer if it's a large read in atomic */
 744		goto read_again;
 745	}
 746
 747	/*
 748	 * Latency break, schedule another poll immediately.
 749	 */
 750	poll_mask |= HVC_POLL_READ;
 751
 752 out:
 753	/* Wakeup write queue if necessary */
 754	if (hp->do_wakeup) {
 755		hp->do_wakeup = 0;
 756		tty_wakeup(tty);
 757	}
 758 bail:
 759	spin_unlock_irqrestore(&hp->lock, flags);
 760
 761	if (read_total) {
 762		/* Activity is occurring, so reset the polling backoff value to
 763		   a minimum for performance. */
 764		timeout = MIN_TIMEOUT;
 765
 766		tty_flip_buffer_push(&hp->port);
 767	}
 768	tty_kref_put(tty);
 769
 770	return poll_mask;
 771}
 772
 773int hvc_poll(struct hvc_struct *hp)
 774{
 775	return __hvc_poll(hp, false);
 776}
 777EXPORT_SYMBOL_GPL(hvc_poll);
 778
 779/**
 780 * __hvc_resize() - Update terminal window size information.
 781 * @hp:		HVC console pointer
 782 * @ws:		Terminal window size structure
 783 *
 784 * Stores the specified window size information in the hvc structure of @hp.
 785 * The function schedule the tty resize update.
 786 *
 787 * Locking:	Locking free; the function MUST be called holding hp->lock
 788 */
 789void __hvc_resize(struct hvc_struct *hp, struct winsize ws)
 790{
 791	hp->ws = ws;
 792	schedule_work(&hp->tty_resize);
 793}
 794EXPORT_SYMBOL_GPL(__hvc_resize);
 795
 796/*
 797 * This kthread is either polling or interrupt driven.  This is determined by
 798 * calling hvc_poll() who determines whether a console adapter support
 799 * interrupts.
 800 */
 801static int khvcd(void *unused)
 802{
 803	int poll_mask;
 804	struct hvc_struct *hp;
 805
 806	set_freezable();
 807	do {
 808		poll_mask = 0;
 809		hvc_kicked = 0;
 810		try_to_freeze();
 811		wmb();
 812		if (!cpus_are_in_xmon()) {
 813			mutex_lock(&hvc_structs_mutex);
 814			list_for_each_entry(hp, &hvc_structs, next) {
 815				poll_mask |= __hvc_poll(hp, true);
 816				cond_resched();
 817			}
 818			mutex_unlock(&hvc_structs_mutex);
 819		} else
 820			poll_mask |= HVC_POLL_READ;
 821		if (hvc_kicked)
 822			continue;
 823		set_current_state(TASK_INTERRUPTIBLE);
 824		if (!hvc_kicked) {
 825			if (poll_mask == 0)
 826				schedule();
 827			else {
 828				unsigned long j_timeout;
 829
 830				if (timeout < MAX_TIMEOUT)
 831					timeout += (timeout >> 6) + 1;
 832
 833				/*
 834				 * We don't use msleep_interruptible otherwise
 835				 * "kick" will fail to wake us up
 836				 */
 837				j_timeout = msecs_to_jiffies(timeout) + 1;
 838				schedule_timeout_interruptible(j_timeout);
 839			}
 840		}
 841		__set_current_state(TASK_RUNNING);
 842	} while (!kthread_should_stop());
 843
 844	return 0;
 845}
 846
 847static int hvc_tiocmget(struct tty_struct *tty)
 848{
 849	struct hvc_struct *hp = tty->driver_data;
 850
 851	if (!hp || !hp->ops->tiocmget)
 852		return -EINVAL;
 853	return hp->ops->tiocmget(hp);
 854}
 855
 856static int hvc_tiocmset(struct tty_struct *tty,
 857			unsigned int set, unsigned int clear)
 858{
 859	struct hvc_struct *hp = tty->driver_data;
 860
 861	if (!hp || !hp->ops->tiocmset)
 862		return -EINVAL;
 863	return hp->ops->tiocmset(hp, set, clear);
 864}
 865
 866#ifdef CONFIG_CONSOLE_POLL
 867static int hvc_poll_init(struct tty_driver *driver, int line, char *options)
 868{
 869	return 0;
 870}
 871
 872static int hvc_poll_get_char(struct tty_driver *driver, int line)
 873{
 874	struct tty_struct *tty = driver->ttys[0];
 875	struct hvc_struct *hp = tty->driver_data;
 876	int n;
 877	char ch;
 878
 879	n = hp->ops->get_chars(hp->vtermno, &ch, 1);
 880
 881	if (n <= 0)
 882		return NO_POLL_CHAR;
 883
 884	return ch;
 885}
 886
 887static void hvc_poll_put_char(struct tty_driver *driver, int line, char ch)
 888{
 889	struct tty_struct *tty = driver->ttys[0];
 890	struct hvc_struct *hp = tty->driver_data;
 891	int n;
 892
 893	do {
 894		n = hp->ops->put_chars(hp->vtermno, &ch, 1);
 895	} while (n <= 0);
 896}
 897#endif
 898
 899static const struct tty_operations hvc_ops = {
 900	.install = hvc_install,
 901	.open = hvc_open,
 902	.close = hvc_close,
 903	.cleanup = hvc_cleanup,
 904	.write = hvc_write,
 905	.hangup = hvc_hangup,
 906	.unthrottle = hvc_unthrottle,
 907	.write_room = hvc_write_room,
 908	.chars_in_buffer = hvc_chars_in_buffer,
 909	.tiocmget = hvc_tiocmget,
 910	.tiocmset = hvc_tiocmset,
 911#ifdef CONFIG_CONSOLE_POLL
 912	.poll_init = hvc_poll_init,
 913	.poll_get_char = hvc_poll_get_char,
 914	.poll_put_char = hvc_poll_put_char,
 915#endif
 916};
 917
 918static const struct tty_port_operations hvc_port_ops = {
 919	.destruct = hvc_port_destruct,
 920};
 921
 922struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
 923			     const struct hv_ops *ops,
 924			     int outbuf_size)
 925{
 926	struct hvc_struct *hp;
 927	int i;
 928
 929	/* We wait until a driver actually comes along */
 930	if (atomic_inc_not_zero(&hvc_needs_init)) {
 931		int err = hvc_init();
 932		if (err)
 933			return ERR_PTR(err);
 934	}
 935
 936	hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
 937			GFP_KERNEL);
 938	if (!hp)
 939		return ERR_PTR(-ENOMEM);
 940
 941	hp->vtermno = vtermno;
 942	hp->data = data;
 943	hp->ops = ops;
 944	hp->outbuf_size = outbuf_size;
 945	hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
 946
 947	tty_port_init(&hp->port);
 948	hp->port.ops = &hvc_port_ops;
 949
 950	INIT_WORK(&hp->tty_resize, hvc_set_winsz);
 951	spin_lock_init(&hp->lock);
 952	mutex_lock(&hvc_structs_mutex);
 953
 954	/*
 955	 * find index to use:
 956	 * see if this vterm id matches one registered for console.
 957	 */
 958	for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
 959		if (vtermnos[i] == hp->vtermno &&
 960		    cons_ops[i] == hp->ops)
 961			break;
 962
 963	/* no matching slot, just use a counter */
 964	if (i >= MAX_NR_HVC_CONSOLES)
 965		i = ++last_hvc;
 966
 967	hp->index = i;
 968	cons_ops[i] = ops;
 969	vtermnos[i] = vtermno;
 970
 971	list_add_tail(&(hp->next), &hvc_structs);
 972	mutex_unlock(&hvc_structs_mutex);
 973
 974	/* check if we need to re-register the kernel console */
 975	hvc_check_console(i);
 976
 977	return hp;
 978}
 979EXPORT_SYMBOL_GPL(hvc_alloc);
 980
 981int hvc_remove(struct hvc_struct *hp)
 982{
 983	unsigned long flags;
 984	struct tty_struct *tty;
 985
 986	tty = tty_port_tty_get(&hp->port);
 987
 988	console_lock();
 989	spin_lock_irqsave(&hp->lock, flags);
 990	if (hp->index < MAX_NR_HVC_CONSOLES) {
 991		vtermnos[hp->index] = -1;
 992		cons_ops[hp->index] = NULL;
 993	}
 994
 995	/* Don't whack hp->irq because tty_hangup() will need to free the irq. */
 996
 997	spin_unlock_irqrestore(&hp->lock, flags);
 998	console_unlock();
 999
1000	/*
1001	 * We 'put' the instance that was grabbed when the kref instance
1002	 * was initialized using kref_init().  Let the last holder of this
1003	 * kref cause it to be removed, which will probably be the tty_vhangup
1004	 * below.
1005	 */
1006	tty_port_put(&hp->port);
1007
1008	/*
1009	 * This function call will auto chain call hvc_hangup.
1010	 */
1011	if (tty) {
1012		tty_vhangup(tty);
1013		tty_kref_put(tty);
1014	}
1015	return 0;
1016}
1017EXPORT_SYMBOL_GPL(hvc_remove);
1018
1019/* Driver initialization: called as soon as someone uses hvc_alloc(). */
1020static int hvc_init(void)
1021{
1022	struct tty_driver *drv;
1023	int err;
1024
1025	/* We need more than hvc_count adapters due to hotplug additions. */
1026	drv = alloc_tty_driver(HVC_ALLOC_TTY_ADAPTERS);
1027	if (!drv) {
1028		err = -ENOMEM;
1029		goto out;
1030	}
1031
1032	drv->driver_name = "hvc";
1033	drv->name = "hvc";
1034	drv->major = HVC_MAJOR;
1035	drv->minor_start = HVC_MINOR;
1036	drv->type = TTY_DRIVER_TYPE_SYSTEM;
1037	drv->init_termios = tty_std_termios;
1038	drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_RESET_TERMIOS;
1039	tty_set_operations(drv, &hvc_ops);
1040
1041	/* Always start the kthread because there can be hotplug vty adapters
1042	 * added later. */
1043	hvc_task = kthread_run(khvcd, NULL, "khvcd");
1044	if (IS_ERR(hvc_task)) {
1045		printk(KERN_ERR "Couldn't create kthread for console.\n");
1046		err = PTR_ERR(hvc_task);
1047		goto put_tty;
1048	}
1049
1050	err = tty_register_driver(drv);
1051	if (err) {
1052		printk(KERN_ERR "Couldn't register hvc console driver\n");
1053		goto stop_thread;
1054	}
1055
1056	/*
1057	 * Make sure tty is fully registered before allowing it to be
1058	 * found by hvc_console_device.
1059	 */
1060	smp_mb();
1061	hvc_driver = drv;
1062	return 0;
1063
1064stop_thread:
1065	kthread_stop(hvc_task);
1066	hvc_task = NULL;
1067put_tty:
1068	put_tty_driver(drv);
1069out:
1070	return err;
1071}