drivers/acpi/acpi_dbg.c

   1 /*
   2  * ACPI AML interfacing support
   3  *
   4  * Copyright (C) 2015, Intel Corporation
   5  * Authors: Lv Zheng <lv.zheng@intel.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 /* #define DEBUG */
  13 #define pr_fmt(fmt) "ACPI: AML: " fmt
  14
  15 #include <linux/kernel.h>
  16 #include <linux/module.h>
  17 #include <linux/wait.h>
  18 #include <linux/poll.h>
  19 #include <linux/sched.h>
  20 #include <linux/kthread.h>
  21 #include <linux/proc_fs.h>
  22 #include <linux/debugfs.h>
  23 #include <linux/circ_buf.h>
  24 #include <linux/acpi.h>
  25 #include "internal.h"
  26
  27 #define ACPI_AML_BUF_ALIGN      (sizeof (acpi_size))
  28 #define ACPI_AML_BUF_SIZE       PAGE_SIZE
  29
  30 #define circ_count(circ) \
  31         (CIRC_CNT((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
  32 #define circ_count_to_end(circ) \
  33         (CIRC_CNT_TO_END((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
  34 #define circ_space(circ) \
  35         (CIRC_SPACE((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
  36 #define circ_space_to_end(circ) \
  37         (CIRC_SPACE_TO_END((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
  38
  39 #define ACPI_AML_OPENED         0x0001
  40 #define ACPI_AML_CLOSED         0x0002
  41 #define ACPI_AML_IN_USER        0x0004 /* user space is writing cmd */
  42 #define ACPI_AML_IN_KERN        0x0008 /* kernel space is reading cmd */
  43 #define ACPI_AML_OUT_USER       0x0010 /* user space is reading log */
  44 #define ACPI_AML_OUT_KERN       0x0020 /* kernel space is writing log */
  45 #define ACPI_AML_USER           (ACPI_AML_IN_USER | ACPI_AML_OUT_USER)
  46 #define ACPI_AML_KERN           (ACPI_AML_IN_KERN | ACPI_AML_OUT_KERN)
  47 #define ACPI_AML_BUSY           (ACPI_AML_USER | ACPI_AML_KERN)
  48 #define ACPI_AML_OPEN           (ACPI_AML_OPENED | ACPI_AML_CLOSED)
  49
  50 struct acpi_aml_io {
  51         wait_queue_head_t wait;
  52         unsigned long flags;
  53         unsigned long users;
  54         struct mutex lock;
  55         struct task_struct *thread;
  56         char out_buf[ACPI_AML_BUF_SIZE] __aligned(ACPI_AML_BUF_ALIGN);
  57         struct circ_buf out_crc;
  58         char in_buf[ACPI_AML_BUF_SIZE] __aligned(ACPI_AML_BUF_ALIGN);
  59         struct circ_buf in_crc;
  60         acpi_osd_exec_callback function;
  61         void *context;
  62         unsigned long usages;
  63 };
  64
  65 static struct acpi_aml_io acpi_aml_io;
  66 static bool acpi_aml_initialized;
  67 static struct file *acpi_aml_active_reader;
  68 static struct dentry *acpi_aml_dentry;
  69
  70 static inline bool __acpi_aml_running(void)
  71 {
  72         return acpi_aml_io.thread ? true : false;
  73 }
  74
  75 static inline bool __acpi_aml_access_ok(unsigned long flag)
  76 {
  77         /*
  78          * The debugger interface is in opened state (OPENED && !CLOSED),
  79          * then it is allowed to access the debugger buffers from either
  80          * user space or the kernel space.
  81          * In addition, for the kernel space, only the debugger thread
  82          * (thread ID matched) is allowed to access.
  83          */
  84         if (!(acpi_aml_io.flags & ACPI_AML_OPENED) ||
  85             (acpi_aml_io.flags & ACPI_AML_CLOSED) ||
  86             !__acpi_aml_running())
  87                 return false;
  88         if ((flag & ACPI_AML_KERN) &&
  89             current != acpi_aml_io.thread)
  90                 return false;
  91         return true;
  92 }
  93
  94 static inline bool __acpi_aml_readable(struct circ_buf *circ, unsigned long flag)
  95 {
  96         /*
  97          * Another read is not in progress and there is data in buffer
  98          * available for read.
  99          */
 100         if (!(acpi_aml_io.flags & flag) && circ_count(circ))
 101                 return true;
 102         return false;
 103 }
 104
 105 static inline bool __acpi_aml_writable(struct circ_buf *circ, unsigned long flag)
 106 {
 107         /*
 108          * Another write is not in progress and there is buffer space
 109          * available for write.
 110          */
 111         if (!(acpi_aml_io.flags & flag) && circ_space(circ))
 112                 return true;
 113         return false;
 114 }
 115
 116 static inline bool __acpi_aml_busy(void)
 117 {
 118         if (acpi_aml_io.flags & ACPI_AML_BUSY)
 119                 return true;
 120         return false;
 121 }
 122
 123 static inline bool __acpi_aml_opened(void)
 124 {
 125         if (acpi_aml_io.flags & ACPI_AML_OPEN)
 126                 return true;
 127         return false;
 128 }
 129
 130 static inline bool __acpi_aml_used(void)
 131 {
 132         return acpi_aml_io.usages ? true : false;
 133 }
 134
 135 static inline bool acpi_aml_running(void)
 136 {
 137         bool ret;
 138
 139         mutex_lock(&acpi_aml_io.lock);
 140         ret = __acpi_aml_running();
 141         mutex_unlock(&acpi_aml_io.lock);
 142         return ret;
 143 }
 144
 145 static bool acpi_aml_busy(void)
 146 {
 147         bool ret;
 148
 149         mutex_lock(&acpi_aml_io.lock);
 150         ret = __acpi_aml_busy();
 151         mutex_unlock(&acpi_aml_io.lock);
 152         return ret;
 153 }
 154
 155 static bool acpi_aml_used(void)
 156 {
 157         bool ret;
 158
 159         /*
 160          * The usage count is prepared to avoid race conditions between the
 161          * starts and the stops of the debugger thread.
 162          */
 163         mutex_lock(&acpi_aml_io.lock);
 164         ret = __acpi_aml_used();
 165         mutex_unlock(&acpi_aml_io.lock);
 166         return ret;
 167 }
 168
 169 static bool acpi_aml_kern_readable(void)
 170 {
 171         bool ret;
 172
 173         mutex_lock(&acpi_aml_io.lock);
 174         ret = !__acpi_aml_access_ok(ACPI_AML_IN_KERN) ||
 175               __acpi_aml_readable(&acpi_aml_io.in_crc, ACPI_AML_IN_KERN);
 176         mutex_unlock(&acpi_aml_io.lock);
 177         return ret;
 178 }
 179
 180 static bool acpi_aml_kern_writable(void)
 181 {
 182         bool ret;
 183
 184         mutex_lock(&acpi_aml_io.lock);
 185         ret = !__acpi_aml_access_ok(ACPI_AML_OUT_KERN) ||
 186               __acpi_aml_writable(&acpi_aml_io.out_crc, ACPI_AML_OUT_KERN);
 187         mutex_unlock(&acpi_aml_io.lock);
 188         return ret;
 189 }
 190
 191 static bool acpi_aml_user_readable(void)
 192 {
 193         bool ret;
 194
 195         mutex_lock(&acpi_aml_io.lock);
 196         ret = !__acpi_aml_access_ok(ACPI_AML_OUT_USER) ||
 197               __acpi_aml_readable(&acpi_aml_io.out_crc, ACPI_AML_OUT_USER);
 198         mutex_unlock(&acpi_aml_io.lock);
 199         return ret;
 200 }
 201
 202 static bool acpi_aml_user_writable(void)
 203 {
 204         bool ret;
 205
 206         mutex_lock(&acpi_aml_io.lock);
 207         ret = !__acpi_aml_access_ok(ACPI_AML_IN_USER) ||
 208               __acpi_aml_writable(&acpi_aml_io.in_crc, ACPI_AML_IN_USER);
 209         mutex_unlock(&acpi_aml_io.lock);
 210         return ret;
 211 }
 212
 213 static int acpi_aml_lock_write(struct circ_buf *circ, unsigned long flag)
 214 {
 215         int ret = 0;
 216
 217         mutex_lock(&acpi_aml_io.lock);
 218         if (!__acpi_aml_access_ok(flag)) {
 219                 ret = -EFAULT;
 220                 goto out;
 221         }
 222         if (!__acpi_aml_writable(circ, flag)) {
 223                 ret = -EAGAIN;
 224                 goto out;
 225         }
 226         acpi_aml_io.flags |= flag;
 227 out:
 228         mutex_unlock(&acpi_aml_io.lock);
 229         return ret;
 230 }
 231
 232 static int acpi_aml_lock_read(struct circ_buf *circ, unsigned long flag)
 233 {
 234         int ret = 0;
 235
 236         mutex_lock(&acpi_aml_io.lock);
 237         if (!__acpi_aml_access_ok(flag)) {
 238                 ret = -EFAULT;
 239                 goto out;
 240         }
 241         if (!__acpi_aml_readable(circ, flag)) {
 242                 ret = -EAGAIN;
 243                 goto out;
 244         }
 245         acpi_aml_io.flags |= flag;
 246 out:
 247         mutex_unlock(&acpi_aml_io.lock);
 248         return ret;
 249 }
 250
 251 static void acpi_aml_unlock_fifo(unsigned long flag, bool wakeup)
 252 {
 253         mutex_lock(&acpi_aml_io.lock);
 254         acpi_aml_io.flags &= ~flag;
 255         if (wakeup)
 256                 wake_up_interruptible(&acpi_aml_io.wait);
 257         mutex_unlock(&acpi_aml_io.lock);
 258 }
 259
 260 static int acpi_aml_write_kern(const char *buf, int len)
 261 {
 262         int ret;
 263         struct circ_buf *crc = &acpi_aml_io.out_crc;
 264         int n;
 265         char *p;
 266
 267         ret = acpi_aml_lock_write(crc, ACPI_AML_OUT_KERN);
 268         if (ret < 0)
 269                 return ret;
 270         /* sync tail before inserting logs */
 271         smp_mb();
 272         p = &crc->buf[crc->head];
 273         n = min(len, circ_space_to_end(crc));
 274         memcpy(p, buf, n);
 275         /* sync head after inserting logs */
 276         smp_wmb();
 277         crc->head = (crc->head + n) & (ACPI_AML_BUF_SIZE - 1);
 278         acpi_aml_unlock_fifo(ACPI_AML_OUT_KERN, true);
 279         return n;
 280 }
 281
 282 static int acpi_aml_readb_kern(void)
 283 {
 284         int ret;
 285         struct circ_buf *crc = &acpi_aml_io.in_crc;
 286         char *p;
 287
 288         ret = acpi_aml_lock_read(crc, ACPI_AML_IN_KERN);
 289         if (ret < 0)
 290                 return ret;
 291         /* sync head before removing cmds */
 292         smp_rmb();
 293         p = &crc->buf[crc->tail];
 294         ret = (int)*p;
 295         /* sync tail before inserting cmds */
 296         smp_mb();
 297         crc->tail = (crc->tail + 1) & (ACPI_AML_BUF_SIZE - 1);
 298         acpi_aml_unlock_fifo(ACPI_AML_IN_KERN, true);
 299         return ret;
 300 }
 301
 302 /*
 303  * acpi_aml_write_log() - Capture debugger output
 304  * @msg: the debugger output
 305  *
 306  * This function should be used to implement acpi_os_printf() to filter out
 307  * the debugger output and store the output into the debugger interface
 308  * buffer. Return the size of stored logs or errno.
 309  */
 310 static ssize_t acpi_aml_write_log(const char *msg)
 311 {
 312         int ret = 0;
 313         int count = 0, size = 0;
 314
 315         if (!acpi_aml_initialized)
 316                 return -ENODEV;
 317         if (msg)
 318                 count = strlen(msg);
 319         while (count > 0) {
 320 again:
 321                 ret = acpi_aml_write_kern(msg + size, count);
 322                 if (ret == -EAGAIN) {
 323                         ret = wait_event_interruptible(acpi_aml_io.wait,
 324                                 acpi_aml_kern_writable());
 325                         /*
 326                          * We need to retry when the condition
 327                          * becomes true.
 328                          */
 329                         if (ret == 0)
 330                                 goto again;
 331                         break;
 332                 }
 333                 if (ret < 0)
 334                         break;
 335                 size += ret;
 336                 count -= ret;
 337         }
 338         return size > 0 ? size : ret;
 339 }
 340
 341 /*
 342  * acpi_aml_read_cmd() - Capture debugger input
 343  * @msg: the debugger input
 344  * @size: the size of the debugger input
 345  *
 346  * This function should be used to implement acpi_os_get_line() to capture
 347  * the debugger input commands and store the input commands into the
 348  * debugger interface buffer. Return the size of stored commands or errno.
 349  */
 350 static ssize_t acpi_aml_read_cmd(char *msg, size_t count)
 351 {
 352         int ret = 0;
 353         int size = 0;
 354
 355         /*
 356          * This is ensured by the running fact of the debugger thread
 357          * unless a bug is introduced.
 358          */
 359         BUG_ON(!acpi_aml_initialized);
 360         while (count > 0) {
 361 again:
 362                 /*
 363                  * Check each input byte to find the end of the command.
 364                  */
 365                 ret = acpi_aml_readb_kern();
 366                 if (ret == -EAGAIN) {
 367                         ret = wait_event_interruptible(acpi_aml_io.wait,
 368                                 acpi_aml_kern_readable());
 369                         /*
 370                          * We need to retry when the condition becomes
 371                          * true.
 372                          */
 373                         if (ret == 0)
 374                                 goto again;
 375                 }
 376                 if (ret < 0)
 377                         break;
 378                 *(msg + size) = (char)ret;
 379                 size++;
 380                 count--;
 381                 if (ret == '\n') {
 382                         /*
 383                          * acpi_os_get_line() requires a zero terminated command
 384                          * string.
 385                          */
 386                         *(msg + size - 1) = '\0';
 387                         break;
 388                 }
 389         }
 390         return size > 0 ? size : ret;
 391 }
 392
 393 static int acpi_aml_thread(void *unsed)
 394 {
 395         acpi_osd_exec_callback function = NULL;
 396         void *context;
 397
 398         mutex_lock(&acpi_aml_io.lock);
 399         if (acpi_aml_io.function) {
 400                 acpi_aml_io.usages++;
 401                 function = acpi_aml_io.function;
 402                 context = acpi_aml_io.context;
 403         }
 404         mutex_unlock(&acpi_aml_io.lock);
 405
 406         if (function)
 407                 function(context);
 408
 409         mutex_lock(&acpi_aml_io.lock);
 410         acpi_aml_io.usages--;
 411         if (!__acpi_aml_used()) {
 412                 acpi_aml_io.thread = NULL;
 413                 wake_up(&acpi_aml_io.wait);
 414         }
 415         mutex_unlock(&acpi_aml_io.lock);
 416
 417         return 0;
 418 }
 419
 420 /*
 421  * acpi_aml_create_thread() - Create AML debugger thread
 422  * @function: the debugger thread callback
 423  * @context: the context to be passed to the debugger thread
 424  *
 425  * This function should be used to implement acpi_os_execute() which is
 426  * used by the ACPICA debugger to create the debugger thread.
 427  */
 428 static int acpi_aml_create_thread(acpi_osd_exec_callback function, void *context)
 429 {
 430         struct task_struct *t;
 431
 432         mutex_lock(&acpi_aml_io.lock);
 433         acpi_aml_io.function = function;
 434         acpi_aml_io.context = context;
 435         mutex_unlock(&acpi_aml_io.lock);
 436
 437         t = kthread_create(acpi_aml_thread, NULL, "aml");
 438         if (IS_ERR(t)) {
 439                 pr_err("Failed to create AML debugger thread.\n");
 440                 return PTR_ERR(t);
 441         }
 442
 443         mutex_lock(&acpi_aml_io.lock);
 444         acpi_aml_io.thread = t;
 445         acpi_set_debugger_thread_id((acpi_thread_id)(unsigned long)t);
 446         wake_up_process(t);
 447         mutex_unlock(&acpi_aml_io.lock);
 448         return 0;
 449 }
 450
 451 static int acpi_aml_wait_command_ready(bool single_step,
 452                                        char *buffer, size_t length)
 453 {
 454         acpi_status status;
 455
 456         if (single_step)
 457                 acpi_os_printf("\n%1c ", ACPI_DEBUGGER_EXECUTE_PROMPT);
 458         else
 459                 acpi_os_printf("\n%1c ", ACPI_DEBUGGER_COMMAND_PROMPT);
 460
 461         status = acpi_os_get_line(buffer, length, NULL);
 462         if (ACPI_FAILURE(status))
 463                 return -EINVAL;
 464         return 0;
 465 }
 466
 467 static int acpi_aml_notify_command_complete(void)
 468 {
 469         return 0;
 470 }
 471
 472 static int acpi_aml_open(struct inode *inode, struct file *file)
 473 {
 474         int ret = 0;
 475         acpi_status status;
 476
 477         mutex_lock(&acpi_aml_io.lock);
 478         /*
 479          * The debugger interface is being closed, no new user is allowed
 480          * during this period.
 481          */
 482         if (acpi_aml_io.flags & ACPI_AML_CLOSED) {
 483                 ret = -EBUSY;
 484                 goto err_lock;
 485         }
 486         if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
 487                 /*
 488                  * Only one reader is allowed to initiate the debugger
 489                  * thread.
 490                  */
 491                 if (acpi_aml_active_reader) {
 492                         ret = -EBUSY;
 493                         goto err_lock;
 494                 } else {
 495                         pr_debug("Opening debugger reader.\n");
 496                         acpi_aml_active_reader = file;
 497                 }
 498         } else {
 499                 /*
 500                  * No writer is allowed unless the debugger thread is
 501                  * ready.
 502                  */
 503                 if (!(acpi_aml_io.flags & ACPI_AML_OPENED)) {
 504                         ret = -ENODEV;
 505                         goto err_lock;
 506                 }
 507         }
 508         if (acpi_aml_active_reader == file) {
 509                 pr_debug("Opening debugger interface.\n");
 510                 mutex_unlock(&acpi_aml_io.lock);
 511
 512                 pr_debug("Initializing debugger thread.\n");
 513                 status = acpi_initialize_debugger();
 514                 if (ACPI_FAILURE(status)) {
 515                         pr_err("Failed to initialize debugger.\n");
 516                         ret = -EINVAL;
 517                         goto err_exit;
 518                 }
 519                 pr_debug("Debugger thread initialized.\n");
 520
 521                 mutex_lock(&acpi_aml_io.lock);
 522                 acpi_aml_io.flags |= ACPI_AML_OPENED;
 523                 acpi_aml_io.out_crc.head = acpi_aml_io.out_crc.tail = 0;
 524                 acpi_aml_io.in_crc.head = acpi_aml_io.in_crc.tail = 0;
 525                 pr_debug("Debugger interface opened.\n");
 526         }
 527         acpi_aml_io.users++;
 528 err_lock:
 529         if (ret < 0) {
 530                 if (acpi_aml_active_reader == file)
 531                         acpi_aml_active_reader = NULL;
 532         }
 533         mutex_unlock(&acpi_aml_io.lock);
 534 err_exit:
 535         return ret;
 536 }
 537
 538 static int acpi_aml_release(struct inode *inode, struct file *file)
 539 {
 540         mutex_lock(&acpi_aml_io.lock);
 541         acpi_aml_io.users--;
 542         if (file == acpi_aml_active_reader) {
 543                 pr_debug("Closing debugger reader.\n");
 544                 acpi_aml_active_reader = NULL;
 545
 546                 pr_debug("Closing debugger interface.\n");
 547                 acpi_aml_io.flags |= ACPI_AML_CLOSED;
 548
 549                 /*
 550                  * Wake up all user space/kernel space blocked
 551                  * readers/writers.
 552                  */
 553                 wake_up_interruptible(&acpi_aml_io.wait);
 554                 mutex_unlock(&acpi_aml_io.lock);
 555                 /*
 556                  * Wait all user space/kernel space readers/writers to
 557                  * stop so that ACPICA command loop of the debugger thread
 558                  * should fail all its command line reads after this point.
 559                  */
 560                 wait_event(acpi_aml_io.wait, !acpi_aml_busy());
 561
 562                 /*
 563                  * Then we try to terminate the debugger thread if it is
 564                  * not terminated.
 565                  */
 566                 pr_debug("Terminating debugger thread.\n");
 567                 acpi_terminate_debugger();
 568                 wait_event(acpi_aml_io.wait, !acpi_aml_used());
 569                 pr_debug("Debugger thread terminated.\n");
 570
 571                 mutex_lock(&acpi_aml_io.lock);
 572                 acpi_aml_io.flags &= ~ACPI_AML_OPENED;
 573         }
 574         if (acpi_aml_io.users == 0) {
 575                 pr_debug("Debugger interface closed.\n");
 576                 acpi_aml_io.flags &= ~ACPI_AML_CLOSED;
 577         }
 578         mutex_unlock(&acpi_aml_io.lock);
 579         return 0;
 580 }
 581
 582 static int acpi_aml_read_user(char __user *buf, int len)
 583 {
 584         int ret;
 585         struct circ_buf *crc = &acpi_aml_io.out_crc;
 586         int n;
 587         char *p;
 588
 589         ret = acpi_aml_lock_read(crc, ACPI_AML_OUT_USER);
 590         if (ret < 0)
 591                 return ret;
 592         /* sync head before removing logs */
 593         smp_rmb();
 594         p = &crc->buf[crc->tail];
 595         n = min(len, circ_count_to_end(crc));
 596         if (copy_to_user(buf, p, n)) {
 597                 ret = -EFAULT;
 598                 goto out;
 599         }
 600         /* sync tail after removing logs */
 601         smp_mb();
 602         crc->tail = (crc->tail + n) & (ACPI_AML_BUF_SIZE - 1);
 603         ret = n;
 604 out:
 605         acpi_aml_unlock_fifo(ACPI_AML_OUT_USER, ret >= 0);
 606         return ret;
 607 }
 608
 609 static ssize_t acpi_aml_read(struct file *file, char __user *buf,
 610                              size_t count, loff_t *ppos)
 611 {
 612         int ret = 0;
 613         int size = 0;
 614
 615         if (!count)
 616                 return 0;
 617         if (!access_ok(VERIFY_WRITE, buf, count))
 618                 return -EFAULT;
 619
 620         while (count > 0) {
 621 again:
 622                 ret = acpi_aml_read_user(buf + size, count);
 623                 if (ret == -EAGAIN) {
 624                         if (file->f_flags & O_NONBLOCK)
 625                                 break;
 626                         else {
 627                                 ret = wait_event_interruptible(acpi_aml_io.wait,
 628                                         acpi_aml_user_readable());
 629                                 /*
 630                                  * We need to retry when the condition
 631                                  * becomes true.
 632                                  */
 633                                 if (ret == 0)
 634                                         goto again;
 635                         }
 636                 }
 637                 if (ret < 0) {
 638                         if (!acpi_aml_running())
 639                                 ret = 0;
 640                         break;
 641                 }
 642                 if (ret) {
 643                         size += ret;
 644                         count -= ret;
 645                         *ppos += ret;
 646                         break;
 647                 }
 648         }
 649         return size > 0 ? size : ret;
 650 }
 651
 652 static int acpi_aml_write_user(const char __user *buf, int len)
 653 {
 654         int ret;
 655         struct circ_buf *crc = &acpi_aml_io.in_crc;
 656         int n;
 657         char *p;
 658
 659         ret = acpi_aml_lock_write(crc, ACPI_AML_IN_USER);
 660         if (ret < 0)
 661                 return ret;
 662         /* sync tail before inserting cmds */
 663         smp_mb();
 664         p = &crc->buf[crc->head];
 665         n = min(len, circ_space_to_end(crc));
 666         if (copy_from_user(p, buf, n)) {
 667                 ret = -EFAULT;
 668                 goto out;
 669         }
 670         /* sync head after inserting cmds */
 671         smp_wmb();
 672         crc->head = (crc->head + n) & (ACPI_AML_BUF_SIZE - 1);
 673         ret = n;
 674 out:
 675         acpi_aml_unlock_fifo(ACPI_AML_IN_USER, ret >= 0);
 676         return n;
 677 }
 678
 679 static ssize_t acpi_aml_write(struct file *file, const char __user *buf,
 680                               size_t count, loff_t *ppos)
 681 {
 682         int ret = 0;
 683         int size = 0;
 684
 685         if (!count)
 686                 return 0;
 687         if (!access_ok(VERIFY_READ, buf, count))
 688                 return -EFAULT;
 689
 690         while (count > 0) {
 691 again:
 692                 ret = acpi_aml_write_user(buf + size, count);
 693                 if (ret == -EAGAIN) {
 694                         if (file->f_flags & O_NONBLOCK)
 695                                 break;
 696                         else {
 697                                 ret = wait_event_interruptible(acpi_aml_io.wait,
 698                                         acpi_aml_user_writable());
 699                                 /*
 700                                  * We need to retry when the condition
 701                                  * becomes true.
 702                                  */
 703                                 if (ret == 0)
 704                                         goto again;
 705                         }
 706                 }
 707                 if (ret < 0) {
 708                         if (!acpi_aml_running())
 709                                 ret = 0;
 710                         break;
 711                 }
 712                 if (ret) {
 713                         size += ret;
 714                         count -= ret;
 715                         *ppos += ret;
 716                 }
 717         }
 718         return size > 0 ? size : ret;
 719 }
 720
 721 static unsigned int acpi_aml_poll(struct file *file, poll_table *wait)
 722 {
 723         int masks = 0;
 724
 725         poll_wait(file, &acpi_aml_io.wait, wait);
 726         if (acpi_aml_user_readable())
 727                 masks |= POLLIN | POLLRDNORM;
 728         if (acpi_aml_user_writable())
 729                 masks |= POLLOUT | POLLWRNORM;
 730
 731         return masks;
 732 }
 733
 734 static const struct file_operations acpi_aml_operations = {
 735         .read           = acpi_aml_read,
 736         .write          = acpi_aml_write,
 737         .poll           = acpi_aml_poll,
 738         .open           = acpi_aml_open,
 739         .release        = acpi_aml_release,
 740         .llseek         = generic_file_llseek,
 741 };
 742
 743 static const struct acpi_debugger_ops acpi_aml_debugger = {
 744         .create_thread           = acpi_aml_create_thread,
 745         .read_cmd                = acpi_aml_read_cmd,
 746         .write_log               = acpi_aml_write_log,
 747         .wait_command_ready      = acpi_aml_wait_command_ready,
 748         .notify_command_complete = acpi_aml_notify_command_complete,
 749 };
 750
 751 int __init acpi_aml_init(void)
 752 {
 753         int ret = 0;
 754
 755         if (!acpi_debugfs_dir) {
 756                 ret = -ENOENT;
 757                 goto err_exit;
 758         }
 759
 760         /* Initialize AML IO interface */
 761         mutex_init(&acpi_aml_io.lock);
 762         init_waitqueue_head(&acpi_aml_io.wait);
 763         acpi_aml_io.out_crc.buf = acpi_aml_io.out_buf;
 764         acpi_aml_io.in_crc.buf = acpi_aml_io.in_buf;
 765         acpi_aml_dentry = debugfs_create_file("acpidbg",
 766                                               S_IFREG | S_IRUGO | S_IWUSR,
 767                                               acpi_debugfs_dir, NULL,
 768                                               &acpi_aml_operations);
 769         if (acpi_aml_dentry == NULL) {
 770                 ret = -ENODEV;
 771                 goto err_exit;
 772         }
 773         ret = acpi_register_debugger(THIS_MODULE, &acpi_aml_debugger);
 774         if (ret)
 775                 goto err_fs;
 776         acpi_aml_initialized = true;
 777
 778 err_fs:
 779         if (ret) {
 780                 debugfs_remove(acpi_aml_dentry);
 781                 acpi_aml_dentry = NULL;
 782         }
 783 err_exit:
 784         return ret;
 785 }
 786
 787 void __exit acpi_aml_exit(void)
 788 {
 789         if (acpi_aml_initialized) {
 790                 acpi_unregister_debugger(&acpi_aml_debugger);
 791                 if (acpi_aml_dentry) {
 792                         debugfs_remove(acpi_aml_dentry);
 793                         acpi_aml_dentry = NULL;
 794                 }
 795                 acpi_aml_initialized = false;
 796         }
 797 }
 798
 799 module_init(acpi_aml_init);
 800 module_exit(acpi_aml_exit);
 801
 802 MODULE_AUTHOR("Lv Zheng");
 803 MODULE_DESCRIPTION("ACPI debugger userspace IO driver");
 804 MODULE_LICENSE("GPL");