linux/drivers/tty/hvc/hvc_console.c
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   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 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 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, 1);
 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, 0);
 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 int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count)
 500{
 501        struct hvc_struct *hp = tty->driver_data;
 502        unsigned long flags;
 503        int 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(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
 926                        GFP_KERNEL);
 927        if (!hp)
 928                return ERR_PTR(-ENOMEM);
 929
 930        hp->vtermno = vtermno;
 931        hp->data = data;
 932        hp->ops = ops;
 933        hp->outbuf_size = outbuf_size;
 934        hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
 935
 936        tty_port_init(&hp->port);
 937        hp->port.ops = &hvc_port_ops;
 938
 939        INIT_WORK(&hp->tty_resize, hvc_set_winsz);
 940        spin_lock_init(&hp->lock);
 941        mutex_lock(&hvc_structs_mutex);
 942
 943        /*
 944         * find index to use:
 945         * see if this vterm id matches one registered for console.
 946         */
 947        for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
 948                if (vtermnos[i] == hp->vtermno &&
 949                    cons_ops[i] == hp->ops)
 950                        break;
 951
 952        if (i >= MAX_NR_HVC_CONSOLES) {
 953
 954                /* find 'empty' slot for console */
 955                for (i = 0; i < MAX_NR_HVC_CONSOLES && vtermnos[i] != -1; i++) {
 956                }
 957
 958                /* no matching slot, just use a counter */
 959                if (i == MAX_NR_HVC_CONSOLES)
 960                        i = ++last_hvc + MAX_NR_HVC_CONSOLES;
 961        }
 962
 963        hp->index = i;
 964        if (i < MAX_NR_HVC_CONSOLES) {
 965                cons_ops[i] = ops;
 966                vtermnos[i] = vtermno;
 967        }
 968
 969        list_add_tail(&(hp->next), &hvc_structs);
 970        mutex_unlock(&hvc_structs_mutex);
 971
 972        /* check if we need to re-register the kernel console */
 973        hvc_check_console(i);
 974
 975        return hp;
 976}
 977EXPORT_SYMBOL_GPL(hvc_alloc);
 978
 979int hvc_remove(struct hvc_struct *hp)
 980{
 981        unsigned long flags;
 982        struct tty_struct *tty;
 983
 984        tty = tty_port_tty_get(&hp->port);
 985
 986        console_lock();
 987        spin_lock_irqsave(&hp->lock, flags);
 988        if (hp->index < MAX_NR_HVC_CONSOLES) {
 989                vtermnos[hp->index] = -1;
 990                cons_ops[hp->index] = NULL;
 991        }
 992
 993        /* Don't whack hp->irq because tty_hangup() will need to free the irq. */
 994
 995        spin_unlock_irqrestore(&hp->lock, flags);
 996        console_unlock();
 997
 998        /*
 999         * We 'put' the instance that was grabbed when the kref instance
1000         * was initialized using kref_init().  Let the last holder of this
1001         * kref cause it to be removed, which will probably be the tty_vhangup
1002         * below.
1003         */
1004        tty_port_put(&hp->port);
1005
1006        /*
1007         * This function call will auto chain call hvc_hangup.
1008         */
1009        if (tty) {
1010                tty_vhangup(tty);
1011                tty_kref_put(tty);
1012        }
1013        return 0;
1014}
1015EXPORT_SYMBOL_GPL(hvc_remove);
1016
1017/* Driver initialization: called as soon as someone uses hvc_alloc(). */
1018static int hvc_init(void)
1019{
1020        struct tty_driver *drv;
1021        int err;
1022
1023        /* We need more than hvc_count adapters due to hotplug additions. */
1024        drv = tty_alloc_driver(HVC_ALLOC_TTY_ADAPTERS, TTY_DRIVER_REAL_RAW |
1025                        TTY_DRIVER_RESET_TERMIOS);
1026        if (IS_ERR(drv)) {
1027                err = PTR_ERR(drv);
1028                goto out;
1029        }
1030
1031        drv->driver_name = "hvc";
1032        drv->name = "hvc";
1033        drv->major = HVC_MAJOR;
1034        drv->minor_start = HVC_MINOR;
1035        drv->type = TTY_DRIVER_TYPE_SYSTEM;
1036        drv->init_termios = tty_std_termios;
1037        tty_set_operations(drv, &hvc_ops);
1038
1039        /* Always start the kthread because there can be hotplug vty adapters
1040         * added later. */
1041        hvc_task = kthread_run(khvcd, NULL, "khvcd");
1042        if (IS_ERR(hvc_task)) {
1043                printk(KERN_ERR "Couldn't create kthread for console.\n");
1044                err = PTR_ERR(hvc_task);
1045                goto put_tty;
1046        }
1047
1048        err = tty_register_driver(drv);
1049        if (err) {
1050                printk(KERN_ERR "Couldn't register hvc console driver\n");
1051                goto stop_thread;
1052        }
1053
1054        /*
1055         * Make sure tty is fully registered before allowing it to be
1056         * found by hvc_console_device.
1057         */
1058        smp_mb();
1059        hvc_driver = drv;
1060        return 0;
1061
1062stop_thread:
1063        kthread_stop(hvc_task);
1064        hvc_task = NULL;
1065put_tty:
1066        tty_driver_kref_put(drv);
1067out:
1068        return err;
1069}
1070