drivers/tty/hvc/hvc

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This source file includes following definitions.
hvc_get_by_index
__hvc_flush
hvc_console_flush
hvc_flush
hvc_console_print
hvc_console_device
hvc_console_setup
hvc_console_init
hvc_port_destruct
hvc_check_console
hvc_instantiate
hvc_kick
hvc_unthrottle
hvc_install
hvc_open
hvc_close
hvc_cleanup
hvc_hangup
hvc_push
hvc_write
hvc_set_winsz
hvc_write_room
hvc_chars_in_buffer
__hvc_poll
hvc_poll
__hvc_resize
khvcd
hvc_tiocmget
hvc_tiocmset
hvc_poll_init
hvc_poll_get_char
hvc_poll_put_char
hvc_alloc
hvc_remove
hvc_init
   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 
  54 static struct tty_driver *hvc_driver;
  55 static struct task_struct *hvc_task;
  56 
  57 /* Picks up late kicks after list walk but before schedule() */
  58 static int hvc_kicked;
  59 
  60 /* hvc_init is triggered from hvc_alloc, i.e. only when actually used */
  61 static atomic_t hvc_needs_init __read_mostly = ATOMIC_INIT(-1);
  62 
  63 static int hvc_init(void);
  64 
  65 #ifdef CONFIG_MAGIC_SYSRQ
  66 static int sysrq_pressed;
  67 #endif
  68 
  69 /* dynamic list of hvc_struct instances */
  70 static LIST_HEAD(hvc_structs);
  71 
  72 /*
  73  * Protect the list of hvc_struct instances from inserts and removals during
  74  * list traversal.
  75  */
  76 static 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  */
  83 static 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  */
  90 static 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 
 113 static 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 
 123 static 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  */
 131 static 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  */
 142 static const struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES];
 143 static 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 
 151 static 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 
 197 static 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 
 206 static 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 
 217 static 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  */
 241 static int __init hvc_console_init(void)
 242 {
 243         register_console(&hvc_console);
 244         return 0;
 245 }
 246 console_initcall(hvc_console_init);
 247 
 248 /* callback when the kboject ref count reaches zero. */
 249 static 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 
 265 static 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  */
 285 int 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         /* check if we need to re-register the kernel console */
 306         hvc_check_console(index);
 307 
 308         return 0;
 309 }
 310 EXPORT_SYMBOL_GPL(hvc_instantiate);
 311 
 312 /* Wake the sleeping khvcd */
 313 void hvc_kick(void)
 314 {
 315         hvc_kicked = 1;
 316         wake_up_process(hvc_task);
 317 }
 318 EXPORT_SYMBOL_GPL(hvc_kick);
 319 
 320 static void hvc_unthrottle(struct tty_struct *tty)
 321 {
 322         hvc_kick();
 323 }
 324 
 325 static 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  */
 347 static 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 
 389 static 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 
 432 static 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 
 439 static 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  */
 476 static 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 
 499 static 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  */
 563 static 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  */
 589 static 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 
 599 static 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)
 618 static 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 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 
 632 static 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 
 762 int hvc_poll(struct hvc_struct *hp)
 763 {
 764         return __hvc_poll(hp, false);
 765 }
 766 EXPORT_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  */
 778 void __hvc_resize(struct hvc_struct *hp, struct winsize ws)
 779 {
 780         hp->ws = ws;
 781         schedule_work(&hp->tty_resize);
 782 }
 783 EXPORT_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  */
 790 static 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 
 836 static 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 
 845 static 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
 856 static int hvc_poll_init(struct tty_driver *driver, int line, char *options)
 857 {
 858         return 0;
 859 }
 860 
 861 static 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 
 876 static 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 
 888 static 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 
 907 static const struct tty_port_operations hvc_port_ops = {
 908         .destruct = hvc_port_destruct,
 909 };
 910 
 911 struct 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 }
 977 EXPORT_SYMBOL_GPL(hvc_alloc);
 978 
 979 int 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 }
1015 EXPORT_SYMBOL_GPL(hvc_remove);
1016 
1017 /* Driver initialization: called as soon as someone uses hvc_alloc(). */
1018 static 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 = alloc_tty_driver(HVC_ALLOC_TTY_ADAPTERS);
1025         if (!drv) {
1026                 err = -ENOMEM;
1027                 goto out;
1028         }
1029 
1030         drv->driver_name = "hvc";
1031         drv->name = "hvc";
1032         drv->major = HVC_MAJOR;
1033         drv->minor_start = HVC_MINOR;
1034         drv->type = TTY_DRIVER_TYPE_SYSTEM;
1035         drv->init_termios = tty_std_termios;
1036         drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_RESET_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 
1062 stop_thread:
1063         kthread_stop(hvc_task);
1064         hvc_task = NULL;
1065 put_tty:
1066         put_tty_driver(drv);
1067 out:
1068         return err;
1069 }
/* [<][>][^][v][top][bottom][index][help] */
root/drivers/tty/hvc/hvc_console.c

DEFINITIONS
