drivers/auxdisplay/charlcd.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Character LCD driver for Linux
   4  *
   5  * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
   6  * Copyright (C) 2016-2017 Glider bvba
   7  */
   8
   9 #include <linux/atomic.h>
  10 #include <linux/ctype.h>
  11 #include <linux/fs.h>
  12 #include <linux/miscdevice.h>
  13 #include <linux/module.h>
  14 #include <linux/notifier.h>
  15 #include <linux/reboot.h>
  16 #include <linux/slab.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/workqueue.h>
  19
  20 #include <generated/utsrelease.h>
  21
  22 #include "charlcd.h"
  23
  24 /* Keep the backlight on this many seconds for each flash */
  25 #define LCD_BL_TEMPO_PERIOD     4
  26
  27 #define LCD_ESCAPE_LEN          24      /* Max chars for LCD escape command */
  28 #define LCD_ESCAPE_CHAR         27      /* Use char 27 for escape command */
  29
  30 struct charlcd_priv {
  31         struct charlcd lcd;
  32
  33         struct delayed_work bl_work;
  34         struct mutex bl_tempo_lock;     /* Protects access to bl_tempo */
  35         bool bl_tempo;
  36
  37         bool must_clear;
  38
  39         /* contains the LCD config state */
  40         unsigned long flags;
  41
  42         /* Current escape sequence and it's length or -1 if outside */
  43         struct {
  44                 char buf[LCD_ESCAPE_LEN + 1];
  45                 int len;
  46         } esc_seq;
  47
  48         unsigned long long drvdata[];
  49 };
  50
  51 #define charlcd_to_priv(p)      container_of(p, struct charlcd_priv, lcd)
  52
  53 /* Device single-open policy control */
  54 static atomic_t charlcd_available = ATOMIC_INIT(1);
  55
  56 /* turn the backlight on or off */
  57 void charlcd_backlight(struct charlcd *lcd, enum charlcd_onoff on)
  58 {
  59         struct charlcd_priv *priv = charlcd_to_priv(lcd);
  60
  61         if (!lcd->ops->backlight)
  62                 return;
  63
  64         mutex_lock(&priv->bl_tempo_lock);
  65         if (!priv->bl_tempo)
  66                 lcd->ops->backlight(lcd, on);
  67         mutex_unlock(&priv->bl_tempo_lock);
  68 }
  69 EXPORT_SYMBOL_GPL(charlcd_backlight);
  70
  71 static void charlcd_bl_off(struct work_struct *work)
  72 {
  73         struct delayed_work *dwork = to_delayed_work(work);
  74         struct charlcd_priv *priv =
  75                 container_of(dwork, struct charlcd_priv, bl_work);
  76
  77         mutex_lock(&priv->bl_tempo_lock);
  78         if (priv->bl_tempo) {
  79                 priv->bl_tempo = false;
  80                 if (!(priv->flags & LCD_FLAG_L))
  81                         priv->lcd.ops->backlight(&priv->lcd, CHARLCD_OFF);
  82         }
  83         mutex_unlock(&priv->bl_tempo_lock);
  84 }
  85
  86 /* turn the backlight on for a little while */
  87 void charlcd_poke(struct charlcd *lcd)
  88 {
  89         struct charlcd_priv *priv = charlcd_to_priv(lcd);
  90
  91         if (!lcd->ops->backlight)
  92                 return;
  93
  94         cancel_delayed_work_sync(&priv->bl_work);
  95
  96         mutex_lock(&priv->bl_tempo_lock);
  97         if (!priv->bl_tempo && !(priv->flags & LCD_FLAG_L))
  98                 lcd->ops->backlight(lcd, CHARLCD_ON);
  99         priv->bl_tempo = true;
 100         schedule_delayed_work(&priv->bl_work, LCD_BL_TEMPO_PERIOD * HZ);
 101         mutex_unlock(&priv->bl_tempo_lock);
 102 }
 103 EXPORT_SYMBOL_GPL(charlcd_poke);
 104
 105 static void charlcd_home(struct charlcd *lcd)
 106 {
 107         lcd->addr.x = 0;
 108         lcd->addr.y = 0;
 109         lcd->ops->home(lcd);
 110 }
 111
 112 static void charlcd_print(struct charlcd *lcd, char c)
 113 {
 114         if (lcd->addr.x >= lcd->width)
 115                 return;
 116
 117         if (lcd->char_conv)
 118                 c = lcd->char_conv[(unsigned char)c];
 119
 120         if (!lcd->ops->print(lcd, c))
 121                 lcd->addr.x++;
 122
 123         /* prevents the cursor from wrapping onto the next line */
 124         if (lcd->addr.x == lcd->width)
 125                 lcd->ops->gotoxy(lcd, lcd->addr.x - 1, lcd->addr.y);
 126 }
 127
 128 static void charlcd_clear_display(struct charlcd *lcd)
 129 {
 130         lcd->ops->clear_display(lcd);
 131         lcd->addr.x = 0;
 132         lcd->addr.y = 0;
 133 }
 134
 135 /*
 136  * Parses a movement command of the form "(.*);", where the group can be
 137  * any number of subcommands of the form "(x|y)[0-9]+".
 138  *
 139  * Returns whether the command is valid. The position arguments are
 140  * only written if the parsing was successful.
 141  *
 142  * For instance:
 143  *   - ";"          returns (<original x>, <original y>).
 144  *   - "x1;"        returns (1, <original y>).
 145  *   - "y2x1;"      returns (1, 2).
 146  *   - "x12y34x56;" returns (56, 34).
 147  *   - ""           fails.
 148  *   - "x"          fails.
 149  *   - "x;"         fails.
 150  *   - "x1"         fails.
 151  *   - "xy12;"      fails.
 152  *   - "x12yy12;"   fails.
 153  *   - "xx"         fails.
 154  */
 155 static bool parse_xy(const char *s, unsigned long *x, unsigned long *y)
 156 {
 157         unsigned long new_x = *x;
 158         unsigned long new_y = *y;
 159         char *p;
 160
 161         for (;;) {
 162                 if (!*s)
 163                         return false;
 164
 165                 if (*s == ';')
 166                         break;
 167
 168                 if (*s == 'x') {
 169                         new_x = simple_strtoul(s + 1, &p, 10);
 170                         if (p == s + 1)
 171                                 return false;
 172                         s = p;
 173                 } else if (*s == 'y') {
 174                         new_y = simple_strtoul(s + 1, &p, 10);
 175                         if (p == s + 1)
 176                                 return false;
 177                         s = p;
 178                 } else {
 179                         return false;
 180                 }
 181         }
 182
 183         *x = new_x;
 184         *y = new_y;
 185         return true;
 186 }
 187
 188 /*
 189  * These are the file operation function for user access to /dev/lcd
 190  * This function can also be called from inside the kernel, by
 191  * setting file and ppos to NULL.
 192  *
 193  */
 194
 195 static inline int handle_lcd_special_code(struct charlcd *lcd)
 196 {
 197         struct charlcd_priv *priv = charlcd_to_priv(lcd);
 198
 199         /* LCD special codes */
 200
 201         int processed = 0;
 202
 203         char *esc = priv->esc_seq.buf + 2;
 204         int oldflags = priv->flags;
 205
 206         /* check for display mode flags */
 207         switch (*esc) {
 208         case 'D':       /* Display ON */
 209                 priv->flags |= LCD_FLAG_D;
 210                 if (priv->flags != oldflags)
 211                         lcd->ops->display(lcd, CHARLCD_ON);
 212
 213                 processed = 1;
 214                 break;
 215         case 'd':       /* Display OFF */
 216                 priv->flags &= ~LCD_FLAG_D;
 217                 if (priv->flags != oldflags)
 218                         lcd->ops->display(lcd, CHARLCD_OFF);
 219
 220                 processed = 1;
 221                 break;
 222         case 'C':       /* Cursor ON */
 223                 priv->flags |= LCD_FLAG_C;
 224                 if (priv->flags != oldflags)
 225                         lcd->ops->cursor(lcd, CHARLCD_ON);
 226
 227                 processed = 1;
 228                 break;
 229         case 'c':       /* Cursor OFF */
 230                 priv->flags &= ~LCD_FLAG_C;
 231                 if (priv->flags != oldflags)
 232                         lcd->ops->cursor(lcd, CHARLCD_OFF);
 233
 234                 processed = 1;
 235                 break;
 236         case 'B':       /* Blink ON */
 237                 priv->flags |= LCD_FLAG_B;
 238                 if (priv->flags != oldflags)
 239                         lcd->ops->blink(lcd, CHARLCD_ON);
 240
 241                 processed = 1;
 242                 break;
 243         case 'b':       /* Blink OFF */
 244                 priv->flags &= ~LCD_FLAG_B;
 245                 if (priv->flags != oldflags)
 246                         lcd->ops->blink(lcd, CHARLCD_OFF);
 247
 248                 processed = 1;
 249                 break;
 250         case '+':       /* Back light ON */
 251                 priv->flags |= LCD_FLAG_L;
 252                 if (priv->flags != oldflags)
 253                         charlcd_backlight(lcd, CHARLCD_ON);
 254
 255                 processed = 1;
 256                 break;
 257         case '-':       /* Back light OFF */
 258                 priv->flags &= ~LCD_FLAG_L;
 259                 if (priv->flags != oldflags)
 260                         charlcd_backlight(lcd, CHARLCD_OFF);
 261
 262                 processed = 1;
 263                 break;
 264         case '*':       /* Flash back light */
 265                 charlcd_poke(lcd);
 266                 processed = 1;
 267                 break;
 268         case 'f':       /* Small Font */
 269                 priv->flags &= ~LCD_FLAG_F;
 270                 if (priv->flags != oldflags)
 271                         lcd->ops->fontsize(lcd, CHARLCD_FONTSIZE_SMALL);
 272
 273                 processed = 1;
 274                 break;
 275         case 'F':       /* Large Font */
 276                 priv->flags |= LCD_FLAG_F;
 277                 if (priv->flags != oldflags)
 278                         lcd->ops->fontsize(lcd, CHARLCD_FONTSIZE_LARGE);
 279
 280                 processed = 1;
 281                 break;
 282         case 'n':       /* One Line */
 283                 priv->flags &= ~LCD_FLAG_N;
 284                 if (priv->flags != oldflags)
 285                         lcd->ops->lines(lcd, CHARLCD_LINES_1);
 286
 287                 processed = 1;
 288                 break;
 289         case 'N':       /* Two Lines */
 290                 priv->flags |= LCD_FLAG_N;
 291                 if (priv->flags != oldflags)
 292                         lcd->ops->lines(lcd, CHARLCD_LINES_2);
 293
 294                 processed = 1;
 295                 break;
 296         case 'l':       /* Shift Cursor Left */
 297                 if (lcd->addr.x > 0) {
 298                         if (!lcd->ops->shift_cursor(lcd, CHARLCD_SHIFT_LEFT))
 299                                 lcd->addr.x--;
 300                 }
 301
 302                 processed = 1;
 303                 break;
 304         case 'r':       /* shift cursor right */
 305                 if (lcd->addr.x < lcd->width) {
 306                         if (!lcd->ops->shift_cursor(lcd, CHARLCD_SHIFT_RIGHT))
 307                                 lcd->addr.x++;
 308                 }
 309
 310                 processed = 1;
 311                 break;
 312         case 'L':       /* shift display left */
 313                 lcd->ops->shift_display(lcd, CHARLCD_SHIFT_LEFT);
 314                 processed = 1;
 315                 break;
 316         case 'R':       /* shift display right */
 317                 lcd->ops->shift_display(lcd, CHARLCD_SHIFT_RIGHT);
 318                 processed = 1;
 319                 break;
 320         case 'k': {     /* kill end of line */
 321                 int x, xs, ys;
 322
 323                 xs = lcd->addr.x;
 324                 ys = lcd->addr.y;
 325                 for (x = lcd->addr.x; x < lcd->width; x++)
 326                         lcd->ops->print(lcd, ' ');
 327
 328                 /* restore cursor position */
 329                 lcd->addr.x = xs;
 330                 lcd->addr.y = ys;
 331                 lcd->ops->gotoxy(lcd, lcd->addr.x, lcd->addr.y);
 332                 processed = 1;
 333                 break;
 334         }
 335         case 'I':       /* reinitialize display */
 336                 lcd->ops->init_display(lcd);
 337                 priv->flags = ((lcd->height > 1) ? LCD_FLAG_N : 0) | LCD_FLAG_D |
 338                         LCD_FLAG_C | LCD_FLAG_B;
 339                 processed = 1;
 340                 break;
 341         case 'G':
 342                 if (lcd->ops->redefine_char)
 343                         processed = lcd->ops->redefine_char(lcd, esc);
 344                 else
 345                         processed = 1;
 346                 break;
 347
 348         case 'x':       /* gotoxy : LxXXX[yYYY]; */
 349         case 'y':       /* gotoxy : LyYYY[xXXX]; */
 350                 if (priv->esc_seq.buf[priv->esc_seq.len - 1] != ';')
 351                         break;
 352
 353                 /* If the command is valid, move to the new address */
 354                 if (parse_xy(esc, &lcd->addr.x, &lcd->addr.y))
 355                         lcd->ops->gotoxy(lcd, lcd->addr.x, lcd->addr.y);
 356
 357                 /* Regardless of its validity, mark as processed */
 358                 processed = 1;
 359                 break;
 360         }
 361
 362         return processed;
 363 }
 364
 365 static void charlcd_write_char(struct charlcd *lcd, char c)
 366 {
 367         struct charlcd_priv *priv = charlcd_to_priv(lcd);
 368
 369         /* first, we'll test if we're in escape mode */
 370         if ((c != '\n') && priv->esc_seq.len >= 0) {
 371                 /* yes, let's add this char to the buffer */
 372                 priv->esc_seq.buf[priv->esc_seq.len++] = c;
 373                 priv->esc_seq.buf[priv->esc_seq.len] = '\0';
 374         } else {
 375                 /* aborts any previous escape sequence */
 376                 priv->esc_seq.len = -1;
 377
 378                 switch (c) {
 379                 case LCD_ESCAPE_CHAR:
 380                         /* start of an escape sequence */
 381                         priv->esc_seq.len = 0;
 382                         priv->esc_seq.buf[priv->esc_seq.len] = '\0';
 383                         break;
 384                 case '\b':
 385                         /* go back one char and clear it */
 386                         if (lcd->addr.x > 0) {
 387                                 /* back one char */
 388                                 if (!lcd->ops->shift_cursor(lcd,
 389                                                         CHARLCD_SHIFT_LEFT))
 390                                         lcd->addr.x--;
 391                         }
 392                         /* replace with a space */
 393                         charlcd_print(lcd, ' ');
 394                         /* back one char again */
 395                         if (!lcd->ops->shift_cursor(lcd, CHARLCD_SHIFT_LEFT))
 396                                 lcd->addr.x--;
 397
 398                         break;
 399                 case '\f':
 400                         /* quickly clear the display */
 401                         charlcd_clear_display(lcd);
 402                         break;
 403                 case '\n':
 404                         /*
 405                          * flush the remainder of the current line and
 406                          * go to the beginning of the next line
 407                          */
 408                         for (; lcd->addr.x < lcd->width; lcd->addr.x++)
 409                                 lcd->ops->print(lcd, ' ');
 410
 411                         lcd->addr.x = 0;
 412                         lcd->addr.y = (lcd->addr.y + 1) % lcd->height;
 413                         lcd->ops->gotoxy(lcd, lcd->addr.x, lcd->addr.y);
 414                         break;
 415                 case '\r':
 416                         /* go to the beginning of the same line */
 417                         lcd->addr.x = 0;
 418                         lcd->ops->gotoxy(lcd, lcd->addr.x, lcd->addr.y);
 419                         break;
 420                 case '\t':
 421                         /* print a space instead of the tab */
 422                         charlcd_print(lcd, ' ');
 423                         break;
 424                 default:
 425                         /* simply print this char */
 426                         charlcd_print(lcd, c);
 427                         break;
 428                 }
 429         }
 430
 431         /*
 432          * now we'll see if we're in an escape mode and if the current
 433          * escape sequence can be understood.
 434          */
 435         if (priv->esc_seq.len >= 2) {
 436                 int processed = 0;
 437
 438                 if (!strcmp(priv->esc_seq.buf, "[2J")) {
 439                         /* clear the display */
 440                         charlcd_clear_display(lcd);
 441                         processed = 1;
 442                 } else if (!strcmp(priv->esc_seq.buf, "[H")) {
 443                         /* cursor to home */
 444                         charlcd_home(lcd);
 445                         processed = 1;
 446                 }
 447                 /* codes starting with ^[[L */
 448                 else if ((priv->esc_seq.len >= 3) &&
 449                          (priv->esc_seq.buf[0] == '[') &&
 450                          (priv->esc_seq.buf[1] == 'L')) {
 451                         processed = handle_lcd_special_code(lcd);
 452                 }
 453
 454                 /* LCD special escape codes */
 455                 /*
 456                  * flush the escape sequence if it's been processed
 457                  * or if it is getting too long.
 458                  */
 459                 if (processed || (priv->esc_seq.len >= LCD_ESCAPE_LEN))
 460                         priv->esc_seq.len = -1;
 461         } /* escape codes */
 462 }
 463
 464 static struct charlcd *the_charlcd;
 465
 466 static ssize_t charlcd_write(struct file *file, const char __user *buf,
 467                              size_t count, loff_t *ppos)
 468 {
 469         const char __user *tmp = buf;
 470         char c;
 471
 472         for (; count-- > 0; (*ppos)++, tmp++) {
 473                 if (((count + 1) & 0x1f) == 0) {
 474                         /*
 475                          * charlcd_write() is invoked as a VFS->write() callback
 476                          * and as such it is always invoked from preemptible
 477                          * context and may sleep.
 478                          */
 479                         cond_resched();
 480                 }
 481
 482                 if (get_user(c, tmp))
 483                         return -EFAULT;
 484
 485                 charlcd_write_char(the_charlcd, c);
 486         }
 487
 488         return tmp - buf;
 489 }
 490
 491 static int charlcd_open(struct inode *inode, struct file *file)
 492 {
 493         struct charlcd_priv *priv = charlcd_to_priv(the_charlcd);
 494         int ret;
 495
 496         ret = -EBUSY;
 497         if (!atomic_dec_and_test(&charlcd_available))
 498                 goto fail;      /* open only once at a time */
 499
 500         ret = -EPERM;
 501         if (file->f_mode & FMODE_READ)  /* device is write-only */
 502                 goto fail;
 503
 504         if (priv->must_clear) {
 505                 priv->lcd.ops->clear_display(&priv->lcd);
 506                 priv->must_clear = false;
 507                 priv->lcd.addr.x = 0;
 508                 priv->lcd.addr.y = 0;
 509         }
 510         return nonseekable_open(inode, file);
 511
 512  fail:
 513         atomic_inc(&charlcd_available);
 514         return ret;
 515 }
 516
 517 static int charlcd_release(struct inode *inode, struct file *file)
 518 {
 519         atomic_inc(&charlcd_available);
 520         return 0;
 521 }
 522
 523 static const struct file_operations charlcd_fops = {
 524         .write   = charlcd_write,
 525         .open    = charlcd_open,
 526         .release = charlcd_release,
 527         .llseek  = no_llseek,
 528 };
 529
 530 static struct miscdevice charlcd_dev = {
 531         .minor  = LCD_MINOR,
 532         .name   = "lcd",
 533         .fops   = &charlcd_fops,
 534 };
 535
 536 static void charlcd_puts(struct charlcd *lcd, const char *s)
 537 {
 538         const char *tmp = s;
 539         int count = strlen(s);
 540
 541         for (; count-- > 0; tmp++) {
 542                 if (((count + 1) & 0x1f) == 0)
 543                         cond_resched();
 544
 545                 charlcd_write_char(lcd, *tmp);
 546         }
 547 }
 548
 549 #ifdef CONFIG_PANEL_BOOT_MESSAGE
 550 #define LCD_INIT_TEXT CONFIG_PANEL_BOOT_MESSAGE
 551 #else
 552 #define LCD_INIT_TEXT "Linux-" UTS_RELEASE "\n"
 553 #endif
 554
 555 #ifdef CONFIG_CHARLCD_BL_ON
 556 #define LCD_INIT_BL "\x1b[L+"
 557 #elif defined(CONFIG_CHARLCD_BL_FLASH)
 558 #define LCD_INIT_BL "\x1b[L*"
 559 #else
 560 #define LCD_INIT_BL "\x1b[L-"
 561 #endif
 562
 563 /* initialize the LCD driver */
 564 static int charlcd_init(struct charlcd *lcd)
 565 {
 566         struct charlcd_priv *priv = charlcd_to_priv(lcd);
 567         int ret;
 568
 569         priv->flags = ((lcd->height > 1) ? LCD_FLAG_N : 0) | LCD_FLAG_D |
 570                       LCD_FLAG_C | LCD_FLAG_B;
 571         if (lcd->ops->backlight) {
 572                 mutex_init(&priv->bl_tempo_lock);
 573                 INIT_DELAYED_WORK(&priv->bl_work, charlcd_bl_off);
 574         }
 575
 576         /*
 577          * before this line, we must NOT send anything to the display.
 578          * Since charlcd_init_display() needs to write data, we have to
 579          * enable mark the LCD initialized just before.
 580          */
 581         if (WARN_ON(!lcd->ops->init_display))
 582                 return -EINVAL;
 583
 584         ret = lcd->ops->init_display(lcd);
 585         if (ret)
 586                 return ret;
 587
 588         /* display a short message */
 589         charlcd_puts(lcd, "\x1b[Lc\x1b[Lb" LCD_INIT_BL LCD_INIT_TEXT);
 590
 591         /* clear the display on the next device opening */
 592         priv->must_clear = true;
 593         charlcd_home(lcd);
 594         return 0;
 595 }
 596
 597 struct charlcd *charlcd_alloc(void)
 598 {
 599         struct charlcd_priv *priv;
 600         struct charlcd *lcd;
 601
 602         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 603         if (!priv)
 604                 return NULL;
 605
 606         priv->esc_seq.len = -1;
 607
 608         lcd = &priv->lcd;
 609
 610         return lcd;
 611 }
 612 EXPORT_SYMBOL_GPL(charlcd_alloc);
 613
 614 void charlcd_free(struct charlcd *lcd)
 615 {
 616         kfree(charlcd_to_priv(lcd));
 617 }
 618 EXPORT_SYMBOL_GPL(charlcd_free);
 619
 620 static int panel_notify_sys(struct notifier_block *this, unsigned long code,
 621                             void *unused)
 622 {
 623         struct charlcd *lcd = the_charlcd;
 624
 625         switch (code) {
 626         case SYS_DOWN:
 627                 charlcd_puts(lcd,
 628                              "\x0cReloading\nSystem...\x1b[Lc\x1b[Lb\x1b[L+");
 629                 break;
 630         case SYS_HALT:
 631                 charlcd_puts(lcd, "\x0cSystem Halted.\x1b[Lc\x1b[Lb\x1b[L+");
 632                 break;
 633         case SYS_POWER_OFF:
 634                 charlcd_puts(lcd, "\x0cPower off.\x1b[Lc\x1b[Lb\x1b[L+");
 635                 break;
 636         default:
 637                 break;
 638         }
 639         return NOTIFY_DONE;
 640 }
 641
 642 static struct notifier_block panel_notifier = {
 643         .notifier_call = panel_notify_sys,
 644 };
 645
 646 int charlcd_register(struct charlcd *lcd)
 647 {
 648         int ret;
 649
 650         ret = charlcd_init(lcd);
 651         if (ret)
 652                 return ret;
 653
 654         ret = misc_register(&charlcd_dev);
 655         if (ret)
 656                 return ret;
 657
 658         the_charlcd = lcd;
 659         register_reboot_notifier(&panel_notifier);
 660         return 0;
 661 }
 662 EXPORT_SYMBOL_GPL(charlcd_register);
 663
 664 int charlcd_unregister(struct charlcd *lcd)
 665 {
 666         struct charlcd_priv *priv = charlcd_to_priv(lcd);
 667
 668         unregister_reboot_notifier(&panel_notifier);
 669         charlcd_puts(lcd, "\x0cLCD driver unloaded.\x1b[Lc\x1b[Lb\x1b[L-");
 670         misc_deregister(&charlcd_dev);
 671         the_charlcd = NULL;
 672         if (lcd->ops->backlight) {
 673                 cancel_delayed_work_sync(&priv->bl_work);
 674                 priv->lcd.ops->backlight(&priv->lcd, CHARLCD_OFF);
 675         }
 676
 677         return 0;
 678 }
 679 EXPORT_SYMBOL_GPL(charlcd_unregister);
 680
 681 MODULE_LICENSE("GPL");