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