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/delay.h>
  12 #include <linux/fs.h>
  13 #include <linux/miscdevice.h>
  14 #include <linux/module.h>
  15 #include <linux/notifier.h>
  16 #include <linux/reboot.h>
  17 #include <linux/slab.h>
  18 #include <linux/uaccess.h>
  19 #include <linux/workqueue.h>
  20
  21 #include <generated/utsrelease.h>
  22
  23 #include <misc/charlcd.h>
  24
  25 #define LCD_MINOR               156
  26
  27 #define DEFAULT_LCD_BWIDTH      40
  28 #define DEFAULT_LCD_HWIDTH      64
  29
  30 /* Keep the backlight on this many seconds for each flash */
  31 #define LCD_BL_TEMPO_PERIOD     4
  32
  33 #define LCD_FLAG_B              0x0004  /* Blink on */
  34 #define LCD_FLAG_C              0x0008  /* Cursor on */
  35 #define LCD_FLAG_D              0x0010  /* Display on */
  36 #define LCD_FLAG_F              0x0020  /* Large font mode */
  37 #define LCD_FLAG_N              0x0040  /* 2-rows mode */
  38 #define LCD_FLAG_L              0x0080  /* Backlight enabled */
  39
  40 /* LCD commands */
  41 #define LCD_CMD_DISPLAY_CLEAR   0x01    /* Clear entire display */
  42
  43 #define LCD_CMD_ENTRY_MODE      0x04    /* Set entry mode */
  44 #define LCD_CMD_CURSOR_INC      0x02    /* Increment cursor */
  45
  46 #define LCD_CMD_DISPLAY_CTRL    0x08    /* Display control */
  47 #define LCD_CMD_DISPLAY_ON      0x04    /* Set display on */
  48 #define LCD_CMD_CURSOR_ON       0x02    /* Set cursor on */
  49 #define LCD_CMD_BLINK_ON        0x01    /* Set blink on */
  50
  51 #define LCD_CMD_SHIFT           0x10    /* Shift cursor/display */
  52 #define LCD_CMD_DISPLAY_SHIFT   0x08    /* Shift display instead of cursor */
  53 #define LCD_CMD_SHIFT_RIGHT     0x04    /* Shift display/cursor to the right */
  54
  55 #define LCD_CMD_FUNCTION_SET    0x20    /* Set function */
  56 #define LCD_CMD_DATA_LEN_8BITS  0x10    /* Set data length to 8 bits */
  57 #define LCD_CMD_TWO_LINES       0x08    /* Set to two display lines */
  58 #define LCD_CMD_FONT_5X10_DOTS  0x04    /* Set char font to 5x10 dots */
  59
  60 #define LCD_CMD_SET_CGRAM_ADDR  0x40    /* Set char generator RAM address */
  61
  62 #define LCD_CMD_SET_DDRAM_ADDR  0x80    /* Set display data RAM address */
  63
  64 #define LCD_ESCAPE_LEN          24      /* Max chars for LCD escape command */
  65 #define LCD_ESCAPE_CHAR         27      /* Use char 27 for escape command */
  66
  67 struct charlcd_priv {
  68         struct charlcd lcd;
  69
  70         struct delayed_work bl_work;
  71         struct mutex bl_tempo_lock;     /* Protects access to bl_tempo */
  72         bool bl_tempo;
  73
  74         bool must_clear;
  75
  76         /* contains the LCD config state */
  77         unsigned long int flags;
  78
  79         /* Contains the LCD X and Y offset */
  80         struct {
  81                 unsigned long int x;
  82                 unsigned long int y;
  83         } addr;
  84
  85         /* Current escape sequence and it's length or -1 if outside */
  86         struct {
  87                 char buf[LCD_ESCAPE_LEN + 1];
  88                 int len;
  89         } esc_seq;
  90
  91         unsigned long long drvdata[0];
  92 };
  93
  94 #define to_priv(p)      container_of(p, struct charlcd_priv, lcd)
  95
  96 /* Device single-open policy control */
  97 static atomic_t charlcd_available = ATOMIC_INIT(1);
  98
  99 /* sleeps that many milliseconds with a reschedule */
 100 static void long_sleep(int ms)
 101 {
 102         schedule_timeout_interruptible(msecs_to_jiffies(ms));
 103 }
 104
 105 /* turn the backlight on or off */
 106 static void charlcd_backlight(struct charlcd *lcd, int on)
 107 {
 108         struct charlcd_priv *priv = to_priv(lcd);
 109
 110         if (!lcd->ops->backlight)
 111                 return;
 112
 113         mutex_lock(&priv->bl_tempo_lock);
 114         if (!priv->bl_tempo)
 115                 lcd->ops->backlight(lcd, on);
 116         mutex_unlock(&priv->bl_tempo_lock);
 117 }
 118
 119 static void charlcd_bl_off(struct work_struct *work)
 120 {
 121         struct delayed_work *dwork = to_delayed_work(work);
 122         struct charlcd_priv *priv =
 123                 container_of(dwork, struct charlcd_priv, bl_work);
 124
 125         mutex_lock(&priv->bl_tempo_lock);
 126         if (priv->bl_tempo) {
 127                 priv->bl_tempo = false;
 128                 if (!(priv->flags & LCD_FLAG_L))
 129                         priv->lcd.ops->backlight(&priv->lcd, 0);
 130         }
 131         mutex_unlock(&priv->bl_tempo_lock);
 132 }
 133
 134 /* turn the backlight on for a little while */
 135 void charlcd_poke(struct charlcd *lcd)
 136 {
 137         struct charlcd_priv *priv = to_priv(lcd);
 138
 139         if (!lcd->ops->backlight)
 140                 return;
 141
 142         cancel_delayed_work_sync(&priv->bl_work);
 143
 144         mutex_lock(&priv->bl_tempo_lock);
 145         if (!priv->bl_tempo && !(priv->flags & LCD_FLAG_L))
 146                 lcd->ops->backlight(lcd, 1);
 147         priv->bl_tempo = true;
 148         schedule_delayed_work(&priv->bl_work, LCD_BL_TEMPO_PERIOD * HZ);
 149         mutex_unlock(&priv->bl_tempo_lock);
 150 }
 151 EXPORT_SYMBOL_GPL(charlcd_poke);
 152
 153 static void charlcd_gotoxy(struct charlcd *lcd)
 154 {
 155         struct charlcd_priv *priv = to_priv(lcd);
 156         unsigned int addr;
 157
 158         /*
 159          * we force the cursor to stay at the end of the
 160          * line if it wants to go farther
 161          */
 162         addr = priv->addr.x < lcd->bwidth ? priv->addr.x & (lcd->hwidth - 1)
 163                                           : lcd->bwidth - 1;
 164         if (priv->addr.y & 1)
 165                 addr += lcd->hwidth;
 166         if (priv->addr.y & 2)
 167                 addr += lcd->bwidth;
 168         lcd->ops->write_cmd(lcd, LCD_CMD_SET_DDRAM_ADDR | addr);
 169 }
 170
 171 static void charlcd_home(struct charlcd *lcd)
 172 {
 173         struct charlcd_priv *priv = to_priv(lcd);
 174
 175         priv->addr.x = 0;
 176         priv->addr.y = 0;
 177         charlcd_gotoxy(lcd);
 178 }
 179
 180 static void charlcd_print(struct charlcd *lcd, char c)
 181 {
 182         struct charlcd_priv *priv = to_priv(lcd);
 183
 184         if (priv->addr.x < lcd->bwidth) {
 185                 if (lcd->char_conv)
 186                         c = lcd->char_conv[(unsigned char)c];
 187                 lcd->ops->write_data(lcd, c);
 188                 priv->addr.x++;
 189
 190                 /* prevents the cursor from wrapping onto the next line */
 191                 if (priv->addr.x == lcd->bwidth)
 192                         charlcd_gotoxy(lcd);
 193         }
 194 }
 195
 196 static void charlcd_clear_fast(struct charlcd *lcd)
 197 {
 198         int pos;
 199
 200         charlcd_home(lcd);
 201
 202         if (lcd->ops->clear_fast)
 203                 lcd->ops->clear_fast(lcd);
 204         else
 205                 for (pos = 0; pos < min(2, lcd->height) * lcd->hwidth; pos++)
 206                         lcd->ops->write_data(lcd, ' ');
 207
 208         charlcd_home(lcd);
 209 }
 210
 211 /* clears the display and resets X/Y */
 212 static void charlcd_clear_display(struct charlcd *lcd)
 213 {
 214         struct charlcd_priv *priv = to_priv(lcd);
 215
 216         lcd->ops->write_cmd(lcd, LCD_CMD_DISPLAY_CLEAR);
 217         priv->addr.x = 0;
 218         priv->addr.y = 0;
 219         /* we must wait a few milliseconds (15) */
 220         long_sleep(15);
 221 }
 222
 223 static int charlcd_init_display(struct charlcd *lcd)
 224 {
 225         void (*write_cmd_raw)(struct charlcd *lcd, int cmd);
 226         struct charlcd_priv *priv = to_priv(lcd);
 227         u8 init;
 228
 229         if (lcd->ifwidth != 4 && lcd->ifwidth != 8)
 230                 return -EINVAL;
 231
 232         priv->flags = ((lcd->height > 1) ? LCD_FLAG_N : 0) | LCD_FLAG_D |
 233                       LCD_FLAG_C | LCD_FLAG_B;
 234
 235         long_sleep(20);         /* wait 20 ms after power-up for the paranoid */
 236
 237         /*
 238          * 8-bit mode, 1 line, small fonts; let's do it 3 times, to make sure
 239          * the LCD is in 8-bit mode afterwards
 240          */
 241         init = LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS;
 242         if (lcd->ifwidth == 4) {
 243                 init >>= 4;
 244                 write_cmd_raw = lcd->ops->write_cmd_raw4;
 245         } else {
 246                 write_cmd_raw = lcd->ops->write_cmd;
 247         }
 248         write_cmd_raw(lcd, init);
 249         long_sleep(10);
 250         write_cmd_raw(lcd, init);
 251         long_sleep(10);
 252         write_cmd_raw(lcd, init);
 253         long_sleep(10);
 254
 255         if (lcd->ifwidth == 4) {
 256                 /* Switch to 4-bit mode, 1 line, small fonts */
 257                 lcd->ops->write_cmd_raw4(lcd, LCD_CMD_FUNCTION_SET >> 4);
 258                 long_sleep(10);
 259         }
 260
 261         /* set font height and lines number */
 262         lcd->ops->write_cmd(lcd,
 263                 LCD_CMD_FUNCTION_SET |
 264                 ((lcd->ifwidth == 8) ? LCD_CMD_DATA_LEN_8BITS : 0) |
 265                 ((priv->flags & LCD_FLAG_F) ? LCD_CMD_FONT_5X10_DOTS : 0) |
 266                 ((priv->flags & LCD_FLAG_N) ? LCD_CMD_TWO_LINES : 0));
 267         long_sleep(10);
 268
 269         /* display off, cursor off, blink off */
 270         lcd->ops->write_cmd(lcd, LCD_CMD_DISPLAY_CTRL);
 271         long_sleep(10);
 272
 273         lcd->ops->write_cmd(lcd,
 274                 LCD_CMD_DISPLAY_CTRL |  /* set display mode */
 275                 ((priv->flags & LCD_FLAG_D) ? LCD_CMD_DISPLAY_ON : 0) |
 276                 ((priv->flags & LCD_FLAG_C) ? LCD_CMD_CURSOR_ON : 0) |
 277                 ((priv->flags & LCD_FLAG_B) ? LCD_CMD_BLINK_ON : 0));
 278
 279         charlcd_backlight(lcd, (priv->flags & LCD_FLAG_L) ? 1 : 0);
 280
 281         long_sleep(10);
 282
 283         /* entry mode set : increment, cursor shifting */
 284         lcd->ops->write_cmd(lcd, LCD_CMD_ENTRY_MODE | LCD_CMD_CURSOR_INC);
 285
 286         charlcd_clear_display(lcd);
 287         return 0;
 288 }
 289
 290 /*
 291  * Parses an unsigned integer from a string, until a non-digit character
 292  * is found. The empty string is not accepted. No overflow checks are done.
 293  *
 294  * Returns whether the parsing was successful. Only in that case
 295  * the output parameters are written to.
 296  *
 297  * TODO: If the kernel adds an inplace version of kstrtoul(), this function
 298  * could be easily replaced by that.
 299  */
 300 static bool parse_n(const char *s, unsigned long *res, const char **next_s)
 301 {
 302         if (!isdigit(*s))
 303                 return false;
 304
 305         *res = 0;
 306         while (isdigit(*s)) {
 307                 *res = *res * 10 + (*s - '0');
 308                 ++s;
 309         }
 310
 311         *next_s = s;
 312         return true;
 313 }
 314
 315 /*
 316  * Parses a movement command of the form "(.*);", where the group can be
 317  * any number of subcommands of the form "(x|y)[0-9]+".
 318  *
 319  * Returns whether the command is valid. The position arguments are
 320  * only written if the parsing was successful.
 321  *
 322  * For instance:
 323  *   - ";"          returns (<original x>, <original y>).
 324  *   - "x1;"        returns (1, <original y>).
 325  *   - "y2x1;"      returns (1, 2).
 326  *   - "x12y34x56;" returns (56, 34).
 327  *   - ""           fails.
 328  *   - "x"          fails.
 329  *   - "x;"         fails.
 330  *   - "x1"         fails.
 331  *   - "xy12;"      fails.
 332  *   - "x12yy12;"   fails.
 333  *   - "xx"         fails.
 334  */
 335 static bool parse_xy(const char *s, unsigned long *x, unsigned long *y)
 336 {
 337         unsigned long new_x = *x;
 338         unsigned long new_y = *y;
 339
 340         for (;;) {
 341                 if (!*s)
 342                         return false;
 343
 344                 if (*s == ';')
 345                         break;
 346
 347                 if (*s == 'x') {
 348                         if (!parse_n(s + 1, &new_x, &s))
 349                                 return false;
 350                 } else if (*s == 'y') {
 351                         if (!parse_n(s + 1, &new_y, &s))
 352                                 return false;
 353                 } else {
 354                         return false;
 355                 }
 356         }
 357
 358         *x = new_x;
 359         *y = new_y;
 360         return true;
 361 }
 362
 363 /*
 364  * These are the file operation function for user access to /dev/lcd
 365  * This function can also be called from inside the kernel, by
 366  * setting file and ppos to NULL.
 367  *
 368  */
 369
 370 static inline int handle_lcd_special_code(struct charlcd *lcd)
 371 {
 372         struct charlcd_priv *priv = to_priv(lcd);
 373
 374         /* LCD special codes */
 375
 376         int processed = 0;
 377
 378         char *esc = priv->esc_seq.buf + 2;
 379         int oldflags = priv->flags;
 380
 381         /* check for display mode flags */
 382         switch (*esc) {
 383         case 'D':       /* Display ON */
 384                 priv->flags |= LCD_FLAG_D;
 385                 processed = 1;
 386                 break;
 387         case 'd':       /* Display OFF */
 388                 priv->flags &= ~LCD_FLAG_D;
 389                 processed = 1;
 390                 break;
 391         case 'C':       /* Cursor ON */
 392                 priv->flags |= LCD_FLAG_C;
 393                 processed = 1;
 394                 break;
 395         case 'c':       /* Cursor OFF */
 396                 priv->flags &= ~LCD_FLAG_C;
 397                 processed = 1;
 398                 break;
 399         case 'B':       /* Blink ON */
 400                 priv->flags |= LCD_FLAG_B;
 401                 processed = 1;
 402                 break;
 403         case 'b':       /* Blink OFF */
 404                 priv->flags &= ~LCD_FLAG_B;
 405                 processed = 1;
 406                 break;
 407         case '+':       /* Back light ON */
 408                 priv->flags |= LCD_FLAG_L;
 409                 processed = 1;
 410                 break;
 411         case '-':       /* Back light OFF */
 412                 priv->flags &= ~LCD_FLAG_L;
 413                 processed = 1;
 414                 break;
 415         case '*':       /* Flash back light */
 416                 charlcd_poke(lcd);
 417                 processed = 1;
 418                 break;
 419         case 'f':       /* Small Font */
 420                 priv->flags &= ~LCD_FLAG_F;
 421                 processed = 1;
 422                 break;
 423         case 'F':       /* Large Font */
 424                 priv->flags |= LCD_FLAG_F;
 425                 processed = 1;
 426                 break;
 427         case 'n':       /* One Line */
 428                 priv->flags &= ~LCD_FLAG_N;
 429                 processed = 1;
 430                 break;
 431         case 'N':       /* Two Lines */
 432                 priv->flags |= LCD_FLAG_N;
 433                 processed = 1;
 434                 break;
 435         case 'l':       /* Shift Cursor Left */
 436                 if (priv->addr.x > 0) {
 437                         /* back one char if not at end of line */
 438                         if (priv->addr.x < lcd->bwidth)
 439                                 lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT);
 440                         priv->addr.x--;
 441                 }
 442                 processed = 1;
 443                 break;
 444         case 'r':       /* shift cursor right */
 445                 if (priv->addr.x < lcd->width) {
 446                         /* allow the cursor to pass the end of the line */
 447                         if (priv->addr.x < (lcd->bwidth - 1))
 448                                 lcd->ops->write_cmd(lcd,
 449                                         LCD_CMD_SHIFT | LCD_CMD_SHIFT_RIGHT);
 450                         priv->addr.x++;
 451                 }
 452                 processed = 1;
 453                 break;
 454         case 'L':       /* shift display left */
 455                 lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT | LCD_CMD_DISPLAY_SHIFT);
 456                 processed = 1;
 457                 break;
 458         case 'R':       /* shift display right */
 459                 lcd->ops->write_cmd(lcd,
 460                                     LCD_CMD_SHIFT | LCD_CMD_DISPLAY_SHIFT |
 461                                     LCD_CMD_SHIFT_RIGHT);
 462                 processed = 1;
 463                 break;
 464         case 'k': {     /* kill end of line */
 465                 int x;
 466
 467                 for (x = priv->addr.x; x < lcd->bwidth; x++)
 468                         lcd->ops->write_data(lcd, ' ');
 469
 470                 /* restore cursor position */
 471                 charlcd_gotoxy(lcd);
 472                 processed = 1;
 473                 break;
 474         }
 475         case 'I':       /* reinitialize display */
 476                 charlcd_init_display(lcd);
 477                 processed = 1;
 478                 break;
 479         case 'G': {
 480                 /* Generator : LGcxxxxx...xx; must have <c> between '0'
 481                  * and '7', representing the numerical ASCII code of the
 482                  * redefined character, and <xx...xx> a sequence of 16
 483                  * hex digits representing 8 bytes for each character.
 484                  * Most LCDs will only use 5 lower bits of the 7 first
 485                  * bytes.
 486                  */
 487
 488                 unsigned char cgbytes[8];
 489                 unsigned char cgaddr;
 490                 int cgoffset;
 491                 int shift;
 492                 char value;
 493                 int addr;
 494
 495                 if (!strchr(esc, ';'))
 496                         break;
 497
 498                 esc++;
 499
 500                 cgaddr = *(esc++) - '0';
 501                 if (cgaddr > 7) {
 502                         processed = 1;
 503                         break;
 504                 }
 505
 506                 cgoffset = 0;
 507                 shift = 0;
 508                 value = 0;
 509                 while (*esc && cgoffset < 8) {
 510                         shift ^= 4;
 511                         if (*esc >= '0' && *esc <= '9') {
 512                                 value |= (*esc - '0') << shift;
 513                         } else if (*esc >= 'A' && *esc <= 'F') {
 514                                 value |= (*esc - 'A' + 10) << shift;
 515                         } else if (*esc >= 'a' && *esc <= 'f') {
 516                                 value |= (*esc - 'a' + 10) << shift;
 517                         } else {
 518                                 esc++;
 519                                 continue;
 520                         }
 521
 522                         if (shift == 0) {
 523                                 cgbytes[cgoffset++] = value;
 524                                 value = 0;
 525                         }
 526
 527                         esc++;
 528                 }
 529
 530                 lcd->ops->write_cmd(lcd, LCD_CMD_SET_CGRAM_ADDR | (cgaddr * 8));
 531                 for (addr = 0; addr < cgoffset; addr++)
 532                         lcd->ops->write_data(lcd, cgbytes[addr]);
 533
 534                 /* ensures that we stop writing to CGRAM */
 535                 charlcd_gotoxy(lcd);
 536                 processed = 1;
 537                 break;
 538         }
 539         case 'x':       /* gotoxy : LxXXX[yYYY]; */
 540         case 'y':       /* gotoxy : LyYYY[xXXX]; */
 541                 if (priv->esc_seq.buf[priv->esc_seq.len - 1] != ';')
 542                         break;
 543
 544                 /* If the command is valid, move to the new address */
 545                 if (parse_xy(esc, &priv->addr.x, &priv->addr.y))
 546                         charlcd_gotoxy(lcd);
 547
 548                 /* Regardless of its validity, mark as processed */
 549                 processed = 1;
 550                 break;
 551         }
 552
 553         /* TODO: This indent party here got ugly, clean it! */
 554         /* Check whether one flag was changed */
 555         if (oldflags == priv->flags)
 556                 return processed;
 557
 558         /* check whether one of B,C,D flags were changed */
 559         if ((oldflags ^ priv->flags) &
 560             (LCD_FLAG_B | LCD_FLAG_C | LCD_FLAG_D))
 561                 /* set display mode */
 562                 lcd->ops->write_cmd(lcd,
 563                         LCD_CMD_DISPLAY_CTRL |
 564                         ((priv->flags & LCD_FLAG_D) ? LCD_CMD_DISPLAY_ON : 0) |
 565                         ((priv->flags & LCD_FLAG_C) ? LCD_CMD_CURSOR_ON : 0) |
 566                         ((priv->flags & LCD_FLAG_B) ? LCD_CMD_BLINK_ON : 0));
 567         /* check whether one of F,N flags was changed */
 568         else if ((oldflags ^ priv->flags) & (LCD_FLAG_F | LCD_FLAG_N))
 569                 lcd->ops->write_cmd(lcd,
 570                         LCD_CMD_FUNCTION_SET |
 571                         ((lcd->ifwidth == 8) ? LCD_CMD_DATA_LEN_8BITS : 0) |
 572                         ((priv->flags & LCD_FLAG_F) ? LCD_CMD_FONT_5X10_DOTS : 0) |
 573                         ((priv->flags & LCD_FLAG_N) ? LCD_CMD_TWO_LINES : 0));
 574         /* check whether L flag was changed */
 575         else if ((oldflags ^ priv->flags) & LCD_FLAG_L)
 576                 charlcd_backlight(lcd, !!(priv->flags & LCD_FLAG_L));
 577
 578         return processed;
 579 }
 580
 581 static void charlcd_write_char(struct charlcd *lcd, char c)
 582 {
 583         struct charlcd_priv *priv = to_priv(lcd);
 584
 585         /* first, we'll test if we're in escape mode */
 586         if ((c != '\n') && priv->esc_seq.len >= 0) {
 587                 /* yes, let's add this char to the buffer */
 588                 priv->esc_seq.buf[priv->esc_seq.len++] = c;
 589                 priv->esc_seq.buf[priv->esc_seq.len] = '\0';
 590         } else {
 591                 /* aborts any previous escape sequence */
 592                 priv->esc_seq.len = -1;
 593
 594                 switch (c) {
 595                 case LCD_ESCAPE_CHAR:
 596                         /* start of an escape sequence */
 597                         priv->esc_seq.len = 0;
 598                         priv->esc_seq.buf[priv->esc_seq.len] = '\0';
 599                         break;
 600                 case '\b':
 601                         /* go back one char and clear it */
 602                         if (priv->addr.x > 0) {
 603                                 /*
 604                                  * check if we're not at the
 605                                  * end of the line
 606                                  */
 607                                 if (priv->addr.x < lcd->bwidth)
 608                                         /* back one char */
 609                                         lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT);
 610                                 priv->addr.x--;
 611                         }
 612                         /* replace with a space */
 613                         lcd->ops->write_data(lcd, ' ');
 614                         /* back one char again */
 615                         lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT);
 616                         break;
 617                 case '\f':
 618                         /* quickly clear the display */
 619                         charlcd_clear_fast(lcd);
 620                         break;
 621                 case '\n':
 622                         /*
 623                          * flush the remainder of the current line and
 624                          * go to the beginning of the next line
 625                          */
 626                         for (; priv->addr.x < lcd->bwidth; priv->addr.x++)
 627                                 lcd->ops->write_data(lcd, ' ');
 628                         priv->addr.x = 0;
 629                         priv->addr.y = (priv->addr.y + 1) % lcd->height;
 630                         charlcd_gotoxy(lcd);
 631                         break;
 632                 case '\r':
 633                         /* go to the beginning of the same line */
 634                         priv->addr.x = 0;
 635                         charlcd_gotoxy(lcd);
 636                         break;
 637                 case '\t':
 638                         /* print a space instead of the tab */
 639                         charlcd_print(lcd, ' ');
 640                         break;
 641                 default:
 642                         /* simply print this char */
 643                         charlcd_print(lcd, c);
 644                         break;
 645                 }
 646         }
 647
 648         /*
 649          * now we'll see if we're in an escape mode and if the current
 650          * escape sequence can be understood.
 651          */
 652         if (priv->esc_seq.len >= 2) {
 653                 int processed = 0;
 654
 655                 if (!strcmp(priv->esc_seq.buf, "[2J")) {
 656                         /* clear the display */
 657                         charlcd_clear_fast(lcd);
 658                         processed = 1;
 659                 } else if (!strcmp(priv->esc_seq.buf, "[H")) {
 660                         /* cursor to home */
 661                         charlcd_home(lcd);
 662                         processed = 1;
 663                 }
 664                 /* codes starting with ^[[L */
 665                 else if ((priv->esc_seq.len >= 3) &&
 666                          (priv->esc_seq.buf[0] == '[') &&
 667                          (priv->esc_seq.buf[1] == 'L')) {
 668                         processed = handle_lcd_special_code(lcd);
 669                 }
 670
 671                 /* LCD special escape codes */
 672                 /*
 673                  * flush the escape sequence if it's been processed
 674                  * or if it is getting too long.
 675                  */
 676                 if (processed || (priv->esc_seq.len >= LCD_ESCAPE_LEN))
 677                         priv->esc_seq.len = -1;
 678         } /* escape codes */
 679 }
 680
 681 static struct charlcd *the_charlcd;
 682
 683 static ssize_t charlcd_write(struct file *file, const char __user *buf,
 684                              size_t count, loff_t *ppos)
 685 {
 686         const char __user *tmp = buf;
 687         char c;
 688
 689         for (; count-- > 0; (*ppos)++, tmp++) {
 690                 if (!in_interrupt() && (((count + 1) & 0x1f) == 0))
 691                         /*
 692                          * let's be a little nice with other processes
 693                          * that need some CPU
 694                          */
 695                         schedule();
 696
 697                 if (get_user(c, tmp))
 698                         return -EFAULT;
 699
 700                 charlcd_write_char(the_charlcd, c);
 701         }
 702
 703         return tmp - buf;
 704 }
 705
 706 static int charlcd_open(struct inode *inode, struct file *file)
 707 {
 708         struct charlcd_priv *priv = to_priv(the_charlcd);
 709         int ret;
 710
 711         ret = -EBUSY;
 712         if (!atomic_dec_and_test(&charlcd_available))
 713                 goto fail;      /* open only once at a time */
 714
 715         ret = -EPERM;
 716         if (file->f_mode & FMODE_READ)  /* device is write-only */
 717                 goto fail;
 718
 719         if (priv->must_clear) {
 720                 charlcd_clear_display(&priv->lcd);
 721                 priv->must_clear = false;
 722         }
 723         return nonseekable_open(inode, file);
 724
 725  fail:
 726         atomic_inc(&charlcd_available);
 727         return ret;
 728 }
 729
 730 static int charlcd_release(struct inode *inode, struct file *file)
 731 {
 732         atomic_inc(&charlcd_available);
 733         return 0;
 734 }
 735
 736 static const struct file_operations charlcd_fops = {
 737         .write   = charlcd_write,
 738         .open    = charlcd_open,
 739         .release = charlcd_release,
 740         .llseek  = no_llseek,
 741 };
 742
 743 static struct miscdevice charlcd_dev = {
 744         .minor  = LCD_MINOR,
 745         .name   = "lcd",
 746         .fops   = &charlcd_fops,
 747 };
 748
 749 static void charlcd_puts(struct charlcd *lcd, const char *s)
 750 {
 751         const char *tmp = s;
 752         int count = strlen(s);
 753
 754         for (; count-- > 0; tmp++) {
 755                 if (!in_interrupt() && (((count + 1) & 0x1f) == 0))
 756                         /*
 757                          * let's be a little nice with other processes
 758                          * that need some CPU
 759                          */
 760                         schedule();
 761
 762                 charlcd_write_char(lcd, *tmp);
 763         }
 764 }
 765
 766 /* initialize the LCD driver */
 767 static int charlcd_init(struct charlcd *lcd)
 768 {
 769         struct charlcd_priv *priv = to_priv(lcd);
 770         int ret;
 771
 772         if (lcd->ops->backlight) {
 773                 mutex_init(&priv->bl_tempo_lock);
 774                 INIT_DELAYED_WORK(&priv->bl_work, charlcd_bl_off);
 775         }
 776
 777         /*
 778          * before this line, we must NOT send anything to the display.
 779          * Since charlcd_init_display() needs to write data, we have to
 780          * enable mark the LCD initialized just before.
 781          */
 782         ret = charlcd_init_display(lcd);
 783         if (ret)
 784                 return ret;
 785
 786         /* display a short message */
 787 #ifdef CONFIG_PANEL_CHANGE_MESSAGE
 788 #ifdef CONFIG_PANEL_BOOT_MESSAGE
 789         charlcd_puts(lcd, "\x1b[Lc\x1b[Lb\x1b[L*" CONFIG_PANEL_BOOT_MESSAGE);
 790 #endif
 791 #else
 792         charlcd_puts(lcd, "\x1b[Lc\x1b[Lb\x1b[L*Linux-" UTS_RELEASE "\n");
 793 #endif
 794         /* clear the display on the next device opening */
 795         priv->must_clear = true;
 796         charlcd_home(lcd);
 797         return 0;
 798 }
 799
 800 struct charlcd *charlcd_alloc(unsigned int drvdata_size)
 801 {
 802         struct charlcd_priv *priv;
 803         struct charlcd *lcd;
 804
 805         priv = kzalloc(sizeof(*priv) + drvdata_size, GFP_KERNEL);
 806         if (!priv)
 807                 return NULL;
 808
 809         priv->esc_seq.len = -1;
 810
 811         lcd = &priv->lcd;
 812         lcd->ifwidth = 8;
 813         lcd->bwidth = DEFAULT_LCD_BWIDTH;
 814         lcd->hwidth = DEFAULT_LCD_HWIDTH;
 815         lcd->drvdata = priv->drvdata;
 816
 817         return lcd;
 818 }
 819 EXPORT_SYMBOL_GPL(charlcd_alloc);
 820
 821 static int panel_notify_sys(struct notifier_block *this, unsigned long code,
 822                             void *unused)
 823 {
 824         struct charlcd *lcd = the_charlcd;
 825
 826         switch (code) {
 827         case SYS_DOWN:
 828                 charlcd_puts(lcd,
 829                              "\x0cReloading\nSystem...\x1b[Lc\x1b[Lb\x1b[L+");
 830                 break;
 831         case SYS_HALT:
 832                 charlcd_puts(lcd, "\x0cSystem Halted.\x1b[Lc\x1b[Lb\x1b[L+");
 833                 break;
 834         case SYS_POWER_OFF:
 835                 charlcd_puts(lcd, "\x0cPower off.\x1b[Lc\x1b[Lb\x1b[L+");
 836                 break;
 837         default:
 838                 break;
 839         }
 840         return NOTIFY_DONE;
 841 }
 842
 843 static struct notifier_block panel_notifier = {
 844         panel_notify_sys,
 845         NULL,
 846         0
 847 };
 848
 849 int charlcd_register(struct charlcd *lcd)
 850 {
 851         int ret;
 852
 853         ret = charlcd_init(lcd);
 854         if (ret)
 855                 return ret;
 856
 857         ret = misc_register(&charlcd_dev);
 858         if (ret)
 859                 return ret;
 860
 861         the_charlcd = lcd;
 862         register_reboot_notifier(&panel_notifier);
 863         return 0;
 864 }
 865 EXPORT_SYMBOL_GPL(charlcd_register);
 866
 867 int charlcd_unregister(struct charlcd *lcd)
 868 {
 869         struct charlcd_priv *priv = to_priv(lcd);
 870
 871         unregister_reboot_notifier(&panel_notifier);
 872         charlcd_puts(lcd, "\x0cLCD driver unloaded.\x1b[Lc\x1b[Lb\x1b[L-");
 873         misc_deregister(&charlcd_dev);
 874         the_charlcd = NULL;
 875         if (lcd->ops->backlight) {
 876                 cancel_delayed_work_sync(&priv->bl_work);
 877                 priv->lcd.ops->backlight(&priv->lcd, 0);
 878         }
 879
 880         return 0;
 881 }
 882 EXPORT_SYMBOL_GPL(charlcd_unregister);
 883
 884 MODULE_LICENSE("GPL");