drivers/acpi/acpi_dbg.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * ACPI AML interfacing support
   4  *
   5  * Copyright (C) 2015, Intel Corporation
   6  * Authors: Lv Zheng <lv.zheng@intel.com>
   7  */
   8
   9 /* #define DEBUG */
  10 #define pr_fmt(fmt) "ACPI: AML: " fmt
  11
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/wait.h>
  15 #include <linux/poll.h>
  16 #include <linux/sched.h>
  17 #include <linux/kthread.h>
  18 #include <linux/proc_fs.h>
  19 #include <linux/debugfs.h>
  20 #include <linux/circ_buf.h>
  21 #include <linux/acpi.h>
  22 #include "internal.h"
  23
  24 #define ACPI_AML_BUF_ALIGN      (sizeof (acpi_size))
  25 #define ACPI_AML_BUF_SIZE       PAGE_SIZE
  26
  27 #define circ_count(circ) \
  28         (CIRC_CNT((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
  29 #define circ_count_to_end(circ) \
  30         (CIRC_CNT_TO_END((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
  31 #define circ_space(circ) \
  32         (CIRC_SPACE((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
  33 #define circ_space_to_end(circ) \
  34         (CIRC_SPACE_TO_END((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
  35
  36 #define ACPI_AML_OPENED         0x0001
  37 #define ACPI_AML_CLOSED         0x0002
  38 #define ACPI_AML_IN_USER        0x0004 /* user space is writing cmd */
  39 #define ACPI_AML_IN_KERN        0x0008 /* kernel space is reading cmd */
  40 #define ACPI_AML_OUT_USER       0x0010 /* user space is reading log */
  41 #define ACPI_AML_OUT_KERN       0x0020 /* kernel space is writing log */
  42 #define ACPI_AML_USER           (ACPI_AML_IN_USER | ACPI_AML_OUT_USER)
  43 #define ACPI_AML_KERN           (ACPI_AML_IN_KERN | ACPI_AML_OUT_KERN)
  44 #define ACPI_AML_BUSY           (ACPI_AML_USER | ACPI_AML_KERN)
  45 #define ACPI_AML_OPEN           (ACPI_AML_OPENED | ACPI_AML_CLOSED)
  46
  47 struct acpi_aml_io {
  48         wait_queue_head_t wait;
  49         unsigned long flags;
  50         unsigned long users;
  51         struct mutex lock;
  52         struct task_struct *thread;
  53         char out_buf[ACPI_AML_BUF_SIZE] __aligned(ACPI_AML_BUF_ALIGN);
  54         struct circ_buf out_crc;
  55         char in_buf[ACPI_AML_BUF_SIZE] __aligned(ACPI_AML_BUF_ALIGN);
  56         struct circ_buf in_crc;
  57         acpi_osd_exec_callback function;
  58         void *context;
  59         unsigned long usages;
  60 };
  61
  62 static struct acpi_aml_io acpi_aml_io;
  63 static bool acpi_aml_initialized;
  64 static struct file *acpi_aml_active_reader;
  65 static struct dentry *acpi_aml_dentry;
  66
  67 static inline bool __acpi_aml_running(void)
  68 {
  69         return acpi_aml_io.thread ? true : false;
  70 }
  71
  72 static inline bool __acpi_aml_access_ok(unsigned long flag)
  73 {
  74         /*
  75          * The debugger interface is in opened state (OPENED && !CLOSED),
  76          * then it is allowed to access the debugger buffers from either
  77          * user space or the kernel space.
  78          * In addition, for the kernel space, only the debugger thread
  79          * (thread ID matched) is allowed to access.
  80          */
  81         if (!(acpi_aml_io.flags & ACPI_AML_OPENED) ||
  82             (acpi_aml_io.flags & ACPI_AML_CLOSED) ||
  83             !__acpi_aml_running())
  84                 return false;
  85         if ((flag & ACPI_AML_KERN) &&
  86             current != acpi_aml_io.thread)
  87                 return false;
  88         return true;
  89 }
  90
  91 static inline bool __acpi_aml_readable(struct circ_buf *circ, unsigned long flag)
  92 {
  93         /*
  94          * Another read is not in progress and there is data in buffer
  95          * available for read.
  96          */
  97         if (!(acpi_aml_io.flags & flag) && circ_count(circ))
  98                 return true;
  99         return false;
 100 }
 101
 102 static inline bool __acpi_aml_writable(struct circ_buf *circ, unsigned long flag)
 103 {
 104         /*
 105          * Another write is not in progress and there is buffer space
 106          * available for write.
 107          */
 108         if (!(acpi_aml_io.flags & flag) && circ_space(circ))
 109                 return true;
 110         return false;
 111 }
 112
 113 static inline bool __acpi_aml_busy(void)
 114 {
 115         if (acpi_aml_io.flags & ACPI_AML_BUSY)
 116                 return true;
 117         return false;
 118 }
 119
 120 static inline bool __acpi_aml_opened(void)
 121 {
 122         if (acpi_aml_io.flags & ACPI_AML_OPEN)
 123                 return true;
 124         return false;
 125 }
 126
 127 static inline bool __acpi_aml_used(void)
 128 {
 129         return acpi_aml_io.usages ? true : false;
 130 }
 131
 132 static inline bool acpi_aml_running(void)
 133 {
 134         bool ret;
 135
 136         mutex_lock(&acpi_aml_io.lock);
 137         ret = __acpi_aml_running();
 138         mutex_unlock(&acpi_aml_io.lock);
 139         return ret;
 140 }
 141
 142 static bool acpi_aml_busy(void)
 143 {
 144         bool ret;
 145
 146         mutex_lock(&acpi_aml_io.lock);
 147         ret = __acpi_aml_busy();
 148         mutex_unlock(&acpi_aml_io.lock);
 149         return ret;
 150 }
 151
 152 static bool acpi_aml_used(void)
 153 {
 154         bool ret;
 155
 156         /*
 157          * The usage count is prepared to avoid race conditions between the
 158          * starts and the stops of the debugger thread.
 159          */
 160         mutex_lock(&acpi_aml_io.lock);
 161         ret = __acpi_aml_used();
 162         mutex_unlock(&acpi_aml_io.lock);
 163         return ret;
 164 }
 165
 166 static bool acpi_aml_kern_readable(void)
 167 {
 168         bool ret;
 169
 170         mutex_lock(&acpi_aml_io.lock);
 171         ret = !__acpi_aml_access_ok(ACPI_AML_IN_KERN) ||
 172               __acpi_aml_readable(&acpi_aml_io.in_crc, ACPI_AML_IN_KERN);
 173         mutex_unlock(&acpi_aml_io.lock);
 174         return ret;
 175 }
 176
 177 static bool acpi_aml_kern_writable(void)
 178 {
 179         bool ret;
 180
 181         mutex_lock(&acpi_aml_io.lock);
 182         ret = !__acpi_aml_access_ok(ACPI_AML_OUT_KERN) ||
 183               __acpi_aml_writable(&acpi_aml_io.out_crc, ACPI_AML_OUT_KERN);
 184         mutex_unlock(&acpi_aml_io.lock);
 185         return ret;
 186 }
 187
 188 static bool acpi_aml_user_readable(void)
 189 {
 190         bool ret;
 191
 192         mutex_lock(&acpi_aml_io.lock);
 193         ret = !__acpi_aml_access_ok(ACPI_AML_OUT_USER) ||
 194               __acpi_aml_readable(&acpi_aml_io.out_crc, ACPI_AML_OUT_USER);
 195         mutex_unlock(&acpi_aml_io.lock);
 196         return ret;
 197 }
 198
 199 static bool acpi_aml_user_writable(void)
 200 {
 201         bool ret;
 202
 203         mutex_lock(&acpi_aml_io.lock);
 204         ret = !__acpi_aml_access_ok(ACPI_AML_IN_USER) ||
 205               __acpi_aml_writable(&acpi_aml_io.in_crc, ACPI_AML_IN_USER);
 206         mutex_unlock(&acpi_aml_io.lock);
 207         return ret;
 208 }
 209
 210 static int acpi_aml_lock_write(struct circ_buf *circ, unsigned long flag)
 211 {
 212         int ret = 0;
 213
 214         mutex_lock(&acpi_aml_io.lock);
 215         if (!__acpi_aml_access_ok(flag)) {
 216                 ret = -EFAULT;
 217                 goto out;
 218         }
 219         if (!__acpi_aml_writable(circ, flag)) {
 220                 ret = -EAGAIN;
 221                 goto out;
 222         }
 223         acpi_aml_io.flags |= flag;
 224 out:
 225         mutex_unlock(&acpi_aml_io.lock);
 226         return ret;
 227 }
 228
 229 static int acpi_aml_lock_read(struct circ_buf *circ, unsigned long flag)
 230 {
 231         int ret = 0;
 232
 233         mutex_lock(&acpi_aml_io.lock);
 234         if (!__acpi_aml_access_ok(flag)) {
 235                 ret = -EFAULT;
 236                 goto out;
 237         }
 238         if (!__acpi_aml_readable(circ, flag)) {
 239                 ret = -EAGAIN;
 240                 goto out;
 241         }
 242         acpi_aml_io.flags |= flag;
 243 out:
 244         mutex_unlock(&acpi_aml_io.lock);
 245         return ret;
 246 }
 247
 248 static void acpi_aml_unlock_fifo(unsigned long flag, bool wakeup)
 249 {
 250         mutex_lock(&acpi_aml_io.lock);
 251         acpi_aml_io.flags &= ~flag;
 252         if (wakeup)
 253                 wake_up_interruptible(&acpi_aml_io.wait);
 254         mutex_unlock(&acpi_aml_io.lock);
 255 }
 256
 257 static int acpi_aml_write_kern(const char *buf, int len)
 258 {
 259         int ret;
 260         struct circ_buf *crc = &acpi_aml_io.out_crc;
 261         int n;
 262         char *p;
 263
 264         ret = acpi_aml_lock_write(crc, ACPI_AML_OUT_KERN);
 265         if (ret < 0)
 266                 return ret;
 267         /* sync tail before inserting logs */
 268         smp_mb();
 269         p = &crc->buf[crc->head];
 270         n = min(len, circ_space_to_end(crc));
 271         memcpy(p, buf, n);
 272         /* sync head after inserting logs */
 273         smp_wmb();
 274         crc->head = (crc->head + n) & (ACPI_AML_BUF_SIZE - 1);
 275         acpi_aml_unlock_fifo(ACPI_AML_OUT_KERN, true);
 276         return n;
 277 }
 278
 279 static int acpi_aml_readb_kern(void)
 280 {
 281         int ret;
 282         struct circ_buf *crc = &acpi_aml_io.in_crc;
 283         char *p;
 284
 285         ret = acpi_aml_lock_read(crc, ACPI_AML_IN_KERN);
 286         if (ret < 0)
 287                 return ret;
 288         /* sync head before removing cmds */
 289         smp_rmb();
 290         p = &crc->buf[crc->tail];
 291         ret = (int)*p;
 292         /* sync tail before inserting cmds */
 293         smp_mb();
 294         crc->tail = (crc->tail + 1) & (ACPI_AML_BUF_SIZE - 1);
 295         acpi_aml_unlock_fifo(ACPI_AML_IN_KERN, true);
 296         return ret;
 297 }
 298
 299 /*
 300  * acpi_aml_write_log() - Capture debugger output
 301  * @msg: the debugger output
 302  *
 303  * This function should be used to implement acpi_os_printf() to filter out
 304  * the debugger output and store the output into the debugger interface
 305  * buffer. Return the size of stored logs or errno.
 306  */
 307 static ssize_t acpi_aml_write_log(const char *msg)
 308 {
 309         int ret = 0;
 310         int count = 0, size = 0;
 311
 312         if (!acpi_aml_initialized)
 313                 return -ENODEV;
 314         if (msg)
 315                 count = strlen(msg);
 316         while (count > 0) {
 317 again:
 318                 ret = acpi_aml_write_kern(msg + size, count);
 319                 if (ret == -EAGAIN) {
 320                         ret = wait_event_interruptible(acpi_aml_io.wait,
 321                                 acpi_aml_kern_writable());
 322                         /*
 323                          * We need to retry when the condition
 324                          * becomes true.
 325                          */
 326                         if (ret == 0)
 327                                 goto again;
 328                         break;
 329                 }
 330                 if (ret < 0)
 331                         break;
 332                 size += ret;
 333                 count -= ret;
 334         }
 335         return size > 0 ? size : ret;
 336 }
 337
 338 /*
 339  * acpi_aml_read_cmd() - Capture debugger input
 340  * @msg: the debugger input
 341  * @size: the size of the debugger input
 342  *
 343  * This function should be used to implement acpi_os_get_line() to capture
 344  * the debugger input commands and store the input commands into the
 345  * debugger interface buffer. Return the size of stored commands or errno.
 346  */
 347 static ssize_t acpi_aml_read_cmd(char *msg, size_t count)
 348 {
 349         int ret = 0;
 350         int size = 0;
 351
 352         /*
 353          * This is ensured by the running fact of the debugger thread
 354          * unless a bug is introduced.
 355          */
 356         BUG_ON(!acpi_aml_initialized);
 357         while (count > 0) {
 358 again:
 359                 /*
 360                  * Check each input byte to find the end of the command.
 361                  */
 362                 ret = acpi_aml_readb_kern();
 363                 if (ret == -EAGAIN) {
 364                         ret = wait_event_interruptible(acpi_aml_io.wait,
 365                                 acpi_aml_kern_readable());
 366                         /*
 367                          * We need to retry when the condition becomes
 368                          * true.
 369                          */
 370                         if (ret == 0)
 371                                 goto again;
 372                 }
 373                 if (ret < 0)
 374                         break;
 375                 *(msg + size) = (char)ret;
 376                 size++;
 377                 count--;
 378                 if (ret == '\n') {
 379                         /*
 380                          * acpi_os_get_line() requires a zero terminated command
 381                          * string.
 382                          */
 383                         *(msg + size - 1) = '\0';
 384                         break;
 385                 }
 386         }
 387         return size > 0 ? size : ret;
 388 }
 389
 390 static int acpi_aml_thread(void *unused)
 391 {
 392         acpi_osd_exec_callback function = NULL;
 393         void *context;
 394
 395         mutex_lock(&acpi_aml_io.lock);
 396         if (acpi_aml_io.function) {
 397                 acpi_aml_io.usages++;
 398                 function = acpi_aml_io.function;
 399                 context = acpi_aml_io.context;
 400         }
 401         mutex_unlock(&acpi_aml_io.lock);
 402
 403         if (function)
 404                 function(context);
 405
 406         mutex_lock(&acpi_aml_io.lock);
 407         acpi_aml_io.usages--;
 408         if (!__acpi_aml_used()) {
 409                 acpi_aml_io.thread = NULL;
 410                 wake_up(&acpi_aml_io.wait);
 411         }
 412         mutex_unlock(&acpi_aml_io.lock);
 413
 414         return 0;
 415 }
 416
 417 /*
 418  * acpi_aml_create_thread() - Create AML debugger thread
 419  * @function: the debugger thread callback
 420  * @context: the context to be passed to the debugger thread
 421  *
 422  * This function should be used to implement acpi_os_execute() which is
 423  * used by the ACPICA debugger to create the debugger thread.
 424  */
 425 static int acpi_aml_create_thread(acpi_osd_exec_callback function, void *context)
 426 {
 427         struct task_struct *t;
 428
 429         mutex_lock(&acpi_aml_io.lock);
 430         acpi_aml_io.function = function;
 431         acpi_aml_io.context = context;
 432         mutex_unlock(&acpi_aml_io.lock);
 433
 434         t = kthread_create(acpi_aml_thread, NULL, "aml");
 435         if (IS_ERR(t)) {
 436                 pr_err("Failed to create AML debugger thread.\n");
 437                 return PTR_ERR(t);
 438         }
 439
 440         mutex_lock(&acpi_aml_io.lock);
 441         acpi_aml_io.thread = t;
 442         acpi_set_debugger_thread_id((acpi_thread_id)(unsigned long)t);
 443         wake_up_process(t);
 444         mutex_unlock(&acpi_aml_io.lock);
 445         return 0;
 446 }
 447
 448 static int acpi_aml_wait_command_ready(bool single_step,
 449                                        char *buffer, size_t length)
 450 {
 451         acpi_status status;
 452
 453         if (single_step)
 454                 acpi_os_printf("\n%1c ", ACPI_DEBUGGER_EXECUTE_PROMPT);
 455         else
 456                 acpi_os_printf("\n%1c ", ACPI_DEBUGGER_COMMAND_PROMPT);
 457
 458         status = acpi_os_get_line(buffer, length, NULL);
 459         if (ACPI_FAILURE(status))
 460                 return -EINVAL;
 461         return 0;
 462 }
 463
 464 static int acpi_aml_notify_command_complete(void)
 465 {
 466         return 0;
 467 }
 468
 469 static int acpi_aml_open(struct inode *inode, struct file *file)
 470 {
 471         int ret = 0;
 472         acpi_status status;
 473
 474         mutex_lock(&acpi_aml_io.lock);
 475         /*
 476          * The debugger interface is being closed, no new user is allowed
 477          * during this period.
 478          */
 479         if (acpi_aml_io.flags & ACPI_AML_CLOSED) {
 480                 ret = -EBUSY;
 481                 goto err_lock;
 482         }
 483         if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
 484                 /*
 485                  * Only one reader is allowed to initiate the debugger
 486                  * thread.
 487                  */
 488                 if (acpi_aml_active_reader) {
 489                         ret = -EBUSY;
 490                         goto err_lock;
 491                 } else {
 492                         pr_debug("Opening debugger reader.\n");
 493                         acpi_aml_active_reader = file;
 494                 }
 495         } else {
 496                 /*
 497                  * No writer is allowed unless the debugger thread is
 498                  * ready.
 499                  */
 500                 if (!(acpi_aml_io.flags & ACPI_AML_OPENED)) {
 501                         ret = -ENODEV;
 502                         goto err_lock;
 503                 }
 504         }
 505         if (acpi_aml_active_reader == file) {
 506                 pr_debug("Opening debugger interface.\n");
 507                 mutex_unlock(&acpi_aml_io.lock);
 508
 509                 pr_debug("Initializing debugger thread.\n");
 510                 status = acpi_initialize_debugger();
 511                 if (ACPI_FAILURE(status)) {
 512                         pr_err("Failed to initialize debugger.\n");
 513                         ret = -EINVAL;
 514                         goto err_exit;
 515                 }
 516                 pr_debug("Debugger thread initialized.\n");
 517
 518                 mutex_lock(&acpi_aml_io.lock);
 519                 acpi_aml_io.flags |= ACPI_AML_OPENED;
 520                 acpi_aml_io.out_crc.head = acpi_aml_io.out_crc.tail = 0;
 521                 acpi_aml_io.in_crc.head = acpi_aml_io.in_crc.tail = 0;
 522                 pr_debug("Debugger interface opened.\n");
 523         }
 524         acpi_aml_io.users++;
 525 err_lock:
 526         if (ret < 0) {
 527                 if (acpi_aml_active_reader == file)
 528                         acpi_aml_active_reader = NULL;
 529         }
 530         mutex_unlock(&acpi_aml_io.lock);
 531 err_exit:
 532         return ret;
 533 }
 534
 535 static int acpi_aml_release(struct inode *inode, struct file *file)
 536 {
 537         mutex_lock(&acpi_aml_io.lock);
 538         acpi_aml_io.users--;
 539         if (file == acpi_aml_active_reader) {
 540                 pr_debug("Closing debugger reader.\n");
 541                 acpi_aml_active_reader = NULL;
 542
 543                 pr_debug("Closing debugger interface.\n");
 544                 acpi_aml_io.flags |= ACPI_AML_CLOSED;
 545
 546                 /*
 547                  * Wake up all user space/kernel space blocked
 548                  * readers/writers.
 549                  */
 550                 wake_up_interruptible(&acpi_aml_io.wait);
 551                 mutex_unlock(&acpi_aml_io.lock);
 552                 /*
 553                  * Wait all user space/kernel space readers/writers to
 554                  * stop so that ACPICA command loop of the debugger thread
 555                  * should fail all its command line reads after this point.
 556                  */
 557                 wait_event(acpi_aml_io.wait, !acpi_aml_busy());
 558
 559                 /*
 560                  * Then we try to terminate the debugger thread if it is
 561                  * not terminated.
 562                  */
 563                 pr_debug("Terminating debugger thread.\n");
 564                 acpi_terminate_debugger();
 565                 wait_event(acpi_aml_io.wait, !acpi_aml_used());
 566                 pr_debug("Debugger thread terminated.\n");
 567
 568                 mutex_lock(&acpi_aml_io.lock);
 569                 acpi_aml_io.flags &= ~ACPI_AML_OPENED;
 570         }
 571         if (acpi_aml_io.users == 0) {
 572                 pr_debug("Debugger interface closed.\n");
 573                 acpi_aml_io.flags &= ~ACPI_AML_CLOSED;
 574         }
 575         mutex_unlock(&acpi_aml_io.lock);
 576         return 0;
 577 }
 578
 579 static int acpi_aml_read_user(char __user *buf, int len)
 580 {
 581         int ret;
 582         struct circ_buf *crc = &acpi_aml_io.out_crc;
 583         int n;
 584         char *p;
 585
 586         ret = acpi_aml_lock_read(crc, ACPI_AML_OUT_USER);
 587         if (ret < 0)
 588                 return ret;
 589         /* sync head before removing logs */
 590         smp_rmb();
 591         p = &crc->buf[crc->tail];
 592         n = min(len, circ_count_to_end(crc));
 593         if (copy_to_user(buf, p, n)) {
 594                 ret = -EFAULT;
 595                 goto out;
 596         }
 597         /* sync tail after removing logs */
 598         smp_mb();
 599         crc->tail = (crc->tail + n) & (ACPI_AML_BUF_SIZE - 1);
 600         ret = n;
 601 out:
 602         acpi_aml_unlock_fifo(ACPI_AML_OUT_USER, ret >= 0);
 603         return ret;
 604 }
 605
 606 static ssize_t acpi_aml_read(struct file *file, char __user *buf,
 607                              size_t count, loff_t *ppos)
 608 {
 609         int ret = 0;
 610         int size = 0;
 611
 612         if (!count)
 613                 return 0;
 614         if (!access_ok(buf, count))
 615                 return -EFAULT;
 616
 617         while (count > 0) {
 618 again:
 619                 ret = acpi_aml_read_user(buf + size, count);
 620                 if (ret == -EAGAIN) {
 621                         if (file->f_flags & O_NONBLOCK)
 622                                 break;
 623                         else {
 624                                 ret = wait_event_interruptible(acpi_aml_io.wait,
 625                                         acpi_aml_user_readable());
 626                                 /*
 627                                  * We need to retry when the condition
 628                                  * becomes true.
 629                                  */
 630                                 if (ret == 0)
 631                                         goto again;
 632                         }
 633                 }
 634                 if (ret < 0) {
 635                         if (!acpi_aml_running())
 636                                 ret = 0;
 637                         break;
 638                 }
 639                 if (ret) {
 640                         size += ret;
 641                         count -= ret;
 642                         *ppos += ret;
 643                         break;
 644                 }
 645         }
 646         return size > 0 ? size : ret;
 647 }
 648
 649 static int acpi_aml_write_user(const char __user *buf, int len)
 650 {
 651         int ret;
 652         struct circ_buf *crc = &acpi_aml_io.in_crc;
 653         int n;
 654         char *p;
 655
 656         ret = acpi_aml_lock_write(crc, ACPI_AML_IN_USER);
 657         if (ret < 0)
 658                 return ret;
 659         /* sync tail before inserting cmds */
 660         smp_mb();
 661         p = &crc->buf[crc->head];
 662         n = min(len, circ_space_to_end(crc));
 663         if (copy_from_user(p, buf, n)) {
 664                 ret = -EFAULT;
 665                 goto out;
 666         }
 667         /* sync head after inserting cmds */
 668         smp_wmb();
 669         crc->head = (crc->head + n) & (ACPI_AML_BUF_SIZE - 1);
 670         ret = n;
 671 out:
 672         acpi_aml_unlock_fifo(ACPI_AML_IN_USER, ret >= 0);
 673         return n;
 674 }
 675
 676 static ssize_t acpi_aml_write(struct file *file, const char __user *buf,
 677                               size_t count, loff_t *ppos)
 678 {
 679         int ret = 0;
 680         int size = 0;
 681
 682         if (!count)
 683                 return 0;
 684         if (!access_ok(buf, count))
 685                 return -EFAULT;
 686
 687         while (count > 0) {
 688 again:
 689                 ret = acpi_aml_write_user(buf + size, count);
 690                 if (ret == -EAGAIN) {
 691                         if (file->f_flags & O_NONBLOCK)
 692                                 break;
 693                         else {
 694                                 ret = wait_event_interruptible(acpi_aml_io.wait,
 695                                         acpi_aml_user_writable());
 696                                 /*
 697                                  * We need to retry when the condition
 698                                  * becomes true.
 699                                  */
 700                                 if (ret == 0)
 701                                         goto again;
 702                         }
 703                 }
 704                 if (ret < 0) {
 705                         if (!acpi_aml_running())
 706                                 ret = 0;
 707                         break;
 708                 }
 709                 if (ret) {
 710                         size += ret;
 711                         count -= ret;
 712                         *ppos += ret;
 713                 }
 714         }
 715         return size > 0 ? size : ret;
 716 }
 717
 718 static __poll_t acpi_aml_poll(struct file *file, poll_table *wait)
 719 {
 720         __poll_t masks = 0;
 721
 722         poll_wait(file, &acpi_aml_io.wait, wait);
 723         if (acpi_aml_user_readable())
 724                 masks |= EPOLLIN | EPOLLRDNORM;
 725         if (acpi_aml_user_writable())
 726                 masks |= EPOLLOUT | EPOLLWRNORM;
 727
 728         return masks;
 729 }
 730
 731 static const struct file_operations acpi_aml_operations = {
 732         .read           = acpi_aml_read,
 733         .write          = acpi_aml_write,
 734         .poll           = acpi_aml_poll,
 735         .open           = acpi_aml_open,
 736         .release        = acpi_aml_release,
 737         .llseek         = generic_file_llseek,
 738 };
 739
 740 static const struct acpi_debugger_ops acpi_aml_debugger = {
 741         .create_thread           = acpi_aml_create_thread,
 742         .read_cmd                = acpi_aml_read_cmd,
 743         .write_log               = acpi_aml_write_log,
 744         .wait_command_ready      = acpi_aml_wait_command_ready,
 745         .notify_command_complete = acpi_aml_notify_command_complete,
 746 };
 747
 748 static int __init acpi_aml_init(void)
 749 {
 750         int ret;
 751
 752         /* Initialize AML IO interface */
 753         mutex_init(&acpi_aml_io.lock);
 754         init_waitqueue_head(&acpi_aml_io.wait);
 755         acpi_aml_io.out_crc.buf = acpi_aml_io.out_buf;
 756         acpi_aml_io.in_crc.buf = acpi_aml_io.in_buf;
 757
 758         acpi_aml_dentry = debugfs_create_file("acpidbg",
 759                                               S_IFREG | S_IRUGO | S_IWUSR,
 760                                               acpi_debugfs_dir, NULL,
 761                                               &acpi_aml_operations);
 762
 763         ret = acpi_register_debugger(THIS_MODULE, &acpi_aml_debugger);
 764         if (ret) {
 765                 debugfs_remove(acpi_aml_dentry);
 766                 acpi_aml_dentry = NULL;
 767                 return ret;
 768         }
 769
 770         acpi_aml_initialized = true;
 771         return 0;
 772 }
 773
 774 static void __exit acpi_aml_exit(void)
 775 {
 776         if (acpi_aml_initialized) {
 777                 acpi_unregister_debugger(&acpi_aml_debugger);
 778                 debugfs_remove(acpi_aml_dentry);
 779                 acpi_aml_dentry = NULL;
 780                 acpi_aml_initialized = false;
 781         }
 782 }
 783
 784 module_init(acpi_aml_init);
 785 module_exit(acpi_aml_exit);
 786
 787 MODULE_AUTHOR("Lv Zheng");
 788 MODULE_DESCRIPTION("ACPI debugger userspace IO driver");
 789 MODULE_LICENSE("GPL");