summaryrefslogtreecommitdiffstats
path: root/drivers/auxdisplay/charlcd.c
blob: 81c22d20d9d9c568ffc2f6c191a407baee330719 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
// SPDX-License-Identifier: GPL-2.0+
/*
 * Character LCD driver for Linux
 *
 * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
 * Copyright (C) 2016-2017 Glider bvba
 */

#include <linux/atomic.h>
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/workqueue.h>

#include <generated/utsrelease.h>

#include <misc/charlcd.h>

#define LCD_MINOR		156

#define DEFAULT_LCD_BWIDTH      40
#define DEFAULT_LCD_HWIDTH      64

/* Keep the backlight on this many seconds for each flash */
#define LCD_BL_TEMPO_PERIOD	4

#define LCD_FLAG_B		0x0004	/* Blink on */
#define LCD_FLAG_C		0x0008	/* Cursor on */
#define LCD_FLAG_D		0x0010	/* Display on */
#define LCD_FLAG_F		0x0020	/* Large font mode */
#define LCD_FLAG_N		0x0040	/* 2-rows mode */
#define LCD_FLAG_L		0x0080	/* Backlight enabled */

/* LCD commands */
#define LCD_CMD_DISPLAY_CLEAR	0x01	/* Clear entire display */

#define LCD_CMD_ENTRY_MODE	0x04	/* Set entry mode */
#define LCD_CMD_CURSOR_INC	0x02	/* Increment cursor */

#define LCD_CMD_DISPLAY_CTRL	0x08	/* Display control */
#define LCD_CMD_DISPLAY_ON	0x04	/* Set display on */
#define LCD_CMD_CURSOR_ON	0x02	/* Set cursor on */
#define LCD_CMD_BLINK_ON	0x01	/* Set blink on */

#define LCD_CMD_SHIFT		0x10	/* Shift cursor/display */
#define LCD_CMD_DISPLAY_SHIFT	0x08	/* Shift display instead of cursor */
#define LCD_CMD_SHIFT_RIGHT	0x04	/* Shift display/cursor to the right */

#define LCD_CMD_FUNCTION_SET	0x20	/* Set function */
#define LCD_CMD_DATA_LEN_8BITS	0x10	/* Set data length to 8 bits */
#define LCD_CMD_TWO_LINES	0x08	/* Set to two display lines */
#define LCD_CMD_FONT_5X10_DOTS	0x04	/* Set char font to 5x10 dots */

#define LCD_CMD_SET_CGRAM_ADDR	0x40	/* Set char generator RAM address */

#define LCD_CMD_SET_DDRAM_ADDR	0x80	/* Set display data RAM address */

#define LCD_ESCAPE_LEN		24	/* Max chars for LCD escape command */
#define LCD_ESCAPE_CHAR		27	/* Use char 27 for escape command */

struct charlcd_priv {
	struct charlcd lcd;

	struct delayed_work bl_work;
	struct mutex bl_tempo_lock;	/* Protects access to bl_tempo */
	bool bl_tempo;

	bool must_clear;

	/* contains the LCD config state */
	unsigned long int flags;

	/* Contains the LCD X and Y offset */
	struct {
		unsigned long int x;
		unsigned long int y;
	} addr;

	/* Current escape sequence and it's length or -1 if outside */
	struct {
		char buf[LCD_ESCAPE_LEN + 1];
		int len;
	} esc_seq;

	unsigned long long drvdata[0];
};

#define to_priv(p)	container_of(p, struct charlcd_priv, lcd)

/* Device single-open policy control */
static atomic_t charlcd_available = ATOMIC_INIT(1);

/* sleeps that many milliseconds with a reschedule */
static void long_sleep(int ms)
{
	schedule_timeout_interruptible(msecs_to_jiffies(ms));
}

/* turn the backlight on or off */
static void charlcd_backlight(struct charlcd *lcd, int on)
{
	struct charlcd_priv *priv = to_priv(lcd);

	if (!lcd->ops->backlight)
		return;

	mutex_lock(&priv->bl_tempo_lock);
	if (!priv->bl_tempo)
		lcd->ops->backlight(lcd, on);
	mutex_unlock(&priv->bl_tempo_lock);
}

static void charlcd_bl_off(struct work_struct *work)
{
	struct delayed_work *dwork = to_delayed_work(work);
	struct charlcd_priv *priv =
		container_of(dwork, struct charlcd_priv, bl_work);

	mutex_lock(&priv->bl_tempo_lock);
	if (priv->bl_tempo) {
		priv->bl_tempo = false;
		if (!(priv->flags & LCD_FLAG_L))
			priv->lcd.ops->backlight(&priv->lcd, 0);
	}
	mutex_unlock(&priv->bl_tempo_lock);
}

/* turn the backlight on for a little while */
void charlcd_poke(struct charlcd *lcd)
{
	struct charlcd_priv *priv = to_priv(lcd);

	if (!lcd->ops->backlight)
		return;

	cancel_delayed_work_sync(&priv->bl_work);

	mutex_lock(&priv->bl_tempo_lock);
	if (!priv->bl_tempo && !(priv->flags & LCD_FLAG_L))
		lcd->ops->backlight(lcd, 1);
	priv->bl_tempo = true;
	schedule_delayed_work(&priv->bl_work, LCD_BL_TEMPO_PERIOD * HZ);
	mutex_unlock(&priv->bl_tempo_lock);
}
EXPORT_SYMBOL_GPL(charlcd_poke);

static void charlcd_gotoxy(struct charlcd *lcd)
{
	struct charlcd_priv *priv = to_priv(lcd);
	unsigned int addr;

	/*
	 * we force the cursor to stay at the end of the
	 * line if it wants to go farther
	 */
	addr = priv->addr.x < lcd->bwidth ? priv->addr.x & (lcd->hwidth - 1)
					  : lcd->bwidth - 1;
	if (priv->addr.y & 1)
		addr += lcd->hwidth;
	if (priv->addr.y & 2)
		addr += lcd->bwidth;
	lcd->ops->write_cmd(lcd, LCD_CMD_SET_DDRAM_ADDR | addr);
}

static void charlcd_home(struct charlcd *lcd)
{
	struct charlcd_priv *priv = to_priv(lcd);

	priv->addr.x = 0;
	priv->addr.y = 0;
	charlcd_gotoxy(lcd);
}

static void charlcd_print(struct charlcd *lcd, char c)
{
	struct charlcd_priv *priv = to_priv(lcd);

	if (priv->addr.x < lcd->bwidth) {
		if (lcd->char_conv)
			c = lcd->char_conv[(unsigned char)c];
		lcd->ops->write_data(lcd, c);
		priv->addr.x++;

		/* prevents the cursor from wrapping onto the next line */
		if (priv->addr.x == lcd->bwidth)
			charlcd_gotoxy(lcd);
	}
}

static void charlcd_clear_fast(struct charlcd *lcd)
{
	int pos;

	charlcd_home(lcd);

	if (lcd->ops->clear_fast)
		lcd->ops->clear_fast(lcd);
	else
		for (pos = 0; pos < min(2, lcd->height) * lcd->hwidth; pos++)
			lcd->ops->write_data(lcd, ' ');

	charlcd_home(lcd);
}

/* clears the display and resets X/Y */
static void charlcd_clear_display(struct charlcd *lcd)
{
	struct charlcd_priv *priv = to_priv(lcd);

	lcd->ops->write_cmd(lcd, LCD_CMD_DISPLAY_CLEAR);
	priv->addr.x = 0;
	priv->addr.y = 0;
	/* we must wait a few milliseconds (15) */
	long_sleep(15);
}

static int charlcd_init_display(struct charlcd *lcd)
{
	void (*write_cmd_raw)(struct charlcd *lcd, int cmd);
	struct charlcd_priv *priv = to_priv(lcd);
	u8 init;

	if (lcd->ifwidth != 4 && lcd->ifwidth != 8)
		return -EINVAL;

	priv->flags = ((lcd->height > 1) ? LCD_FLAG_N : 0) | LCD_FLAG_D |
		      LCD_FLAG_C | LCD_FLAG_B;

	long_sleep(20);		/* wait 20 ms after power-up for the paranoid */

	/*
	 * 8-bit mode, 1 line, small fonts; let's do it 3 times, to make sure
	 * the LCD is in 8-bit mode afterwards
	 */
	init = LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS;
	if (lcd->ifwidth == 4) {
		init >>= 4;
		write_cmd_raw = lcd->ops->write_cmd_raw4;
	} else {
		write_cmd_raw = lcd->ops->write_cmd;
	}
	write_cmd_raw(lcd, init);
	long_sleep(10);
	write_cmd_raw(lcd, init);
	long_sleep(10);
	write_cmd_raw(lcd, init);
	long_sleep(10);

	if (lcd->ifwidth == 4) {
		/* Switch to 4-bit mode, 1 line, small fonts */
		lcd->ops->write_cmd_raw4(lcd, LCD_CMD_FUNCTION_SET >> 4);
		long_sleep(10);
	}

	/* set font height and lines number */
	lcd->ops->write_cmd(lcd,
		LCD_CMD_FUNCTION_SET |
		((lcd->ifwidth == 8) ? LCD_CMD_DATA_LEN_8BITS : 0) |
		((priv->flags & LCD_FLAG_F) ? LCD_CMD_FONT_5X10_DOTS : 0) |
		((priv->flags & LCD_FLAG_N) ? LCD_CMD_TWO_LINES : 0));
	long_sleep(10);

	/* display off, cursor off, blink off */
	lcd->ops->write_cmd(lcd, LCD_CMD_DISPLAY_CTRL);
	long_sleep(10);

	lcd->ops->write_cmd(lcd,
		LCD_CMD_DISPLAY_CTRL |	/* set display mode */
		((priv->flags & LCD_FLAG_D) ? LCD_CMD_DISPLAY_ON : 0) |
		((priv->flags & LCD_FLAG_C) ? LCD_CMD_CURSOR_ON : 0) |
		((priv->flags & LCD_FLAG_B) ? LCD_CMD_BLINK_ON : 0));

	charlcd_backlight(lcd, (priv->flags & LCD_FLAG_L) ? 1 : 0);

	long_sleep(10);

	/* entry mode set : increment, cursor shifting */
	lcd->ops->write_cmd(lcd, LCD_CMD_ENTRY_MODE | LCD_CMD_CURSOR_INC);

	charlcd_clear_display(lcd);
	return 0;
}

/*
 * Parses an unsigned integer from a string, until a non-digit character
 * is found. The empty string is not accepted. No overflow checks are done.
 *
 * Returns whether the parsing was successful. Only in that case
 * the output parameters are written to.
 *
 * TODO: If the kernel adds an inplace version of kstrtoul(), this function
 * could be easily replaced by that.
 */
static bool parse_n(const char *s, unsigned long *res, const char **next_s)
{
	if (!isdigit(*s))
		return false;

	*res = 0;
	while (isdigit(*s)) {
		*res = *res * 10 + (*s - '0');
		++s;
	}

	*next_s = s;
	return true;
}

/*
 * Parses a movement command of the form "(.*);", where the group can be
 * any number of subcommands of the form "(x|y)[0-9]+".
 *
 * Returns whether the command is valid. The position arguments are
 * only written if the parsing was successful.
 *
 * For instance:
 *   - ";"          returns (<original x>, <original y>).
 *   - "x1;"        returns (1, <original y>).
 *   - "y2x1;"      returns (1, 2).
 *   - "x12y34x56;" returns (56, 34).
 *   - ""           fails.
 *   - "x"          fails.
 *   - "x;"         fails.
 *   - "x1"         fails.
 *   - "xy12;"      fails.
 *   - "x12yy12;"   fails.
 *   - "xx"         fails.
 */
static bool parse_xy(const char *s, unsigned long *x, unsigned long *y)
{
	unsigned long new_x = *x;
	unsigned long new_y = *y;

	for (;;) {
		if (!*s)
			return false;

		if (*s == ';')
			break;

		if (*s == 'x') {
			if (!parse_n(s + 1, &new_x, &s))
				return false;
		} else if (*s == 'y') {
			if (!parse_n(s + 1, &new_y, &s))
				return false;
		} else {
			return false;
		}
	}

	*x = new_x;
	*y = new_y;
	return true;
}

/*
 * These are the file operation function for user access to /dev/lcd
 * This function can also be called from inside the kernel, by
 * setting file and ppos to NULL.
 *
 */

static inline int handle_lcd_special_code(struct charlcd *lcd)
{
	struct charlcd_priv *priv = to_priv(lcd);

	/* LCD special codes */

	int processed = 0;

	char *esc = priv->esc_seq.buf + 2;
	int oldflags = priv->flags;

	/* check for display mode flags */
	switch (*esc) {
	case 'D':	/* Display ON */
		priv->flags |= LCD_FLAG_D;
		processed = 1;
		break;
	case 'd':	/* Display OFF */
		priv->flags &= ~LCD_FLAG_D;
		processed = 1;
		break;
	case 'C':	/* Cursor ON */
		priv->flags |= LCD_FLAG_C;
		processed = 1;
		break;
	case 'c':	/* Cursor OFF */
		priv->flags &= ~LCD_FLAG_C;
		processed = 1;
		break;
	case 'B':	/* Blink ON */
		priv->flags |= LCD_FLAG_B;
		processed = 1;
		break;
	case 'b':	/* Blink OFF */
		priv->flags &= ~LCD_FLAG_B;
		processed = 1;
		break;
	case '+':	/* Back light ON */
		priv->flags |= LCD_FLAG_L;
		processed = 1;
		break;
	case '-':	/* Back light OFF */
		priv->flags &= ~LCD_FLAG_L;
		processed = 1;
		break;
	case '*':	/* Flash back light */
		charlcd_poke(lcd);
		processed = 1;
		break;
	case 'f':	/* Small Font */
		priv->flags &= ~LCD_FLAG_F;
		processed = 1;
		break;
	case 'F':	/* Large Font */
		priv->flags |= LCD_FLAG_F;
		processed = 1;
		break;
	case 'n':	/* One Line */
		priv->flags &= ~LCD_FLAG_N;
		processed = 1;
		break;
	case 'N':	/* Two Lines */
		priv->flags |= LCD_FLAG_N;
		processed = 1;
		break;
	case 'l':	/* Shift Cursor Left */
		if (priv->addr.x > 0) {
			/* back one char if not at end of line */
			if (priv->addr.x < lcd->bwidth)
				lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT);
			priv->addr.x--;
		}
		processed = 1;
		break;
	case 'r':	/* shift cursor right */
		if (priv->addr.x < lcd->width) {
			/* allow the cursor to pass the end of the line */
			if (priv->addr.x < (lcd->bwidth - 1))
				lcd->ops->write_cmd(lcd,
					LCD_CMD_SHIFT | LCD_CMD_SHIFT_RIGHT);
			priv->addr.x++;
		}
		processed = 1;
		break;
	case 'L':	/* shift display left */
		lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT | LCD_CMD_DISPLAY_SHIFT);
		processed = 1;
		break;
	case 'R':	/* shift display right */
		lcd->ops->write_cmd(lcd,
				    LCD_CMD_SHIFT | LCD_CMD_DISPLAY_SHIFT |
				    LCD_CMD_SHIFT_RIGHT);
		processed = 1;
		break;
	case 'k': {	/* kill end of line */
		int x;

		for (x = priv->addr.x; x < lcd->bwidth; x++)
			lcd->ops->write_data(lcd, ' ');

		/* restore cursor position */
		charlcd_gotoxy(lcd);
		processed = 1;
		break;
	}
	case 'I':	/* reinitialize display */
		charlcd_init_display(lcd);
		processed = 1;
		break;
	case 'G': {
		/* Generator : LGcxxxxx...xx; must have <c> between '0'
		 * and '7', representing the numerical ASCII code of the
		 * redefined character, and <xx...xx> a sequence of 16
		 * hex digits representing 8 bytes for each character.
		 * Most LCDs will only use 5 lower bits of the 7 first
		 * bytes.
		 */

		unsigned char cgbytes[8];
		unsigned char cgaddr;
		int cgoffset;
		int shift;
		char value;
		int addr;

		if (!strchr(esc, ';'))
			break;

		esc++;

		cgaddr = *(esc++) - '0';
		if (cgaddr > 7) {
			processed = 1;
			break;
		}

		cgoffset = 0;
		shift = 0;
		value = 0;
		while (*esc && cgoffset < 8) {
			shift ^= 4;
			if (*esc >= '0' && *esc <= '9') {
				value |= (*esc - '0') << shift;
			} else if (*esc >= 'A' && *esc <= 'F') {
				value |= (*esc - 'A' + 10) << shift;
			} else if (*esc >= 'a' && *esc <= 'f') {
				value |= (*esc - 'a' + 10) << shift;
			} else {
				esc++;
				continue;
			}

			if (shift == 0) {
				cgbytes[cgoffset++] = value;
				value = 0;
			}

			esc++;
		}

		lcd->ops->write_cmd(lcd, LCD_CMD_SET_CGRAM_ADDR | (cgaddr * 8));
		for (addr = 0; addr < cgoffset; addr++)
			lcd->ops->write_data(lcd, cgbytes[addr]);

		/* ensures that we stop writing to CGRAM */
		charlcd_gotoxy(lcd);
		processed = 1;
		break;
	}
	case 'x':	/* gotoxy : LxXXX[yYYY]; */
	case 'y':	/* gotoxy : LyYYY[xXXX]; */
		/* If the command is valid, move to the new address */
		if (parse_xy(esc, &priv->addr.x, &priv->addr.y))
			charlcd_gotoxy(lcd);

		/* Regardless of its validity, mark as processed */
		processed = 1;
		break;
	}

	/* TODO: This indent party here got ugly, clean it! */
	/* Check whether one flag was changed */
	if (oldflags == priv->flags)
		return processed;

	/* check whether one of B,C,D flags were changed */
	if ((oldflags ^ priv->flags) &
	    (LCD_FLAG_B | LCD_FLAG_C | LCD_FLAG_D))
		/* set display mode */
		lcd->ops->write_cmd(lcd,
			LCD_CMD_DISPLAY_CTRL |
			((priv->flags & LCD_FLAG_D) ? LCD_CMD_DISPLAY_ON : 0) |
			((priv->flags & LCD_FLAG_C) ? LCD_CMD_CURSOR_ON : 0) |
			((priv->flags & LCD_FLAG_B) ? LCD_CMD_BLINK_ON : 0));
	/* check whether one of F,N flags was changed */
	else if ((oldflags ^ priv->flags) & (LCD_FLAG_F | LCD_FLAG_N))
		lcd->ops->write_cmd(lcd,
			LCD_CMD_FUNCTION_SET |
			((lcd->ifwidth == 8) ? LCD_CMD_DATA_LEN_8BITS : 0) |
			((priv->flags & LCD_FLAG_F) ? LCD_CMD_FONT_5X10_DOTS : 0) |
			((priv->flags & LCD_FLAG_N) ? LCD_CMD_TWO_LINES : 0));
	/* check whether L flag was changed */
	else if ((oldflags ^ priv->flags) & LCD_FLAG_L)
		charlcd_backlight(lcd, !!(priv->flags & LCD_FLAG_L));

	return processed;
}

static void charlcd_write_char(struct charlcd *lcd, char c)
{
	struct charlcd_priv *priv = to_priv(lcd);

	/* first, we'll test if we're in escape mode */
	if ((c != '\n') && priv->esc_seq.len >= 0) {
		/* yes, let's add this char to the buffer */
		priv->esc_seq.buf[priv->esc_seq.len++] = c;
		priv->esc_seq.buf[priv->esc_seq.len] = '\0';
	} else {
		/* aborts any previous escape sequence */
		priv->esc_seq.len = -1;

		switch (c) {
		case LCD_ESCAPE_CHAR:
			/* start of an escape sequence */
			priv->esc_seq.len = 0;
			priv->esc_seq.buf[priv->esc_seq.len] = '\0';
			break;
		case '\b':
			/* go back one char and clear it */
			if (priv->addr.x > 0) {
				/*
				 * check if we're not at the
				 * end of the line
				 */
				if (priv->addr.x < lcd->bwidth)
					/* back one char */
					lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT);
				priv->addr.x--;
			}
			/* replace with a space */
			lcd->ops->write_data(lcd, ' ');
			/* back one char again */
			lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT);
			break;
		case '\f':
			/* quickly clear the display */
			charlcd_clear_fast(lcd);
			break;
		case '\n':
			/*
			 * flush the remainder of the current line and
			 * go to the beginning of the next line
			 */
			for (; priv->addr.x < lcd->bwidth; priv->addr.x++)
				lcd->ops->write_data(lcd, ' ');
			priv->addr.x = 0;
			priv->addr.y = (priv->addr.y + 1) % lcd->height;
			charlcd_gotoxy(lcd);
			break;
		case '\r':
			/* go to the beginning of the same line */
			priv->addr.x = 0;
			charlcd_gotoxy(lcd);
			break;
		case '\t':
			/* print a space instead of the tab */
			charlcd_print(lcd, ' ');
			break;
		default:
			/* simply print this char */
			charlcd_print(lcd, c);
			break;
		}
	}

	/*
	 * now we'll see if we're in an escape mode and if the current
	 * escape sequence can be understood.
	 */
	if (priv->esc_seq.len >= 2) {
		int processed = 0;

		if (!strcmp(priv->esc_seq.buf, "[2J")) {
			/* clear the display */
			charlcd_clear_fast(lcd);
			processed = 1;
		} else if (!strcmp(priv->esc_seq.buf, "[H")) {
			/* cursor to home */
			charlcd_home(lcd);
			processed = 1;
		}
		/* codes starting with ^[[L */
		else if ((priv->esc_seq.len >= 3) &&
			 (priv->esc_seq.buf[0] == '[') &&
			 (priv->esc_seq.buf[1] == 'L')) {
			processed = handle_lcd_special_code(lcd);
		}

		/* LCD special escape codes */
		/*
		 * flush the escape sequence if it's been processed
		 * or if it is getting too long.
		 */
		if (processed || (priv->esc_seq.len >= LCD_ESCAPE_LEN))
			priv->esc_seq.len = -1;
	} /* escape codes */
}

static struct charlcd *the_charlcd;

static ssize_t charlcd_write(struct file *file, const char __user *buf,
			     size_t count, loff_t *ppos)
{
	const char __user *tmp = buf;
	char c;

	for (; count-- > 0; (*ppos)++, tmp++) {
		if (!in_interrupt() && (((count + 1) & 0x1f) == 0))
			/*
			 * let's be a little nice with other processes
			 * that need some CPU
			 */
			schedule();

		if (get_user(c, tmp))
			return -EFAULT;

		charlcd_write_char(the_charlcd, c);
	}

	return tmp - buf;
}

static int charlcd_open(struct inode *inode, struct file *file)
{
	struct charlcd_priv *priv = to_priv(the_charlcd);
	int ret;

	ret = -EBUSY;
	if (!atomic_dec_and_test(&charlcd_available))
		goto fail;	/* open only once at a time */

	ret = -EPERM;
	if (file->f_mode & FMODE_READ)	/* device is write-only */
		goto fail;

	if (priv->must_clear) {
		charlcd_clear_display(&priv->lcd);
		priv->must_clear = false;
	}
	return nonseekable_open(inode, file);

 fail:
	atomic_inc(&charlcd_available);
	return ret;
}

static int charlcd_release(struct inode *inode, struct file *file)
{
	atomic_inc(&charlcd_available);
	return 0;
}

static const struct file_operations charlcd_fops = {
	.write   = charlcd_write,
	.open    = charlcd_open,
	.release = charlcd_release,
	.llseek  = no_llseek,
};

static struct miscdevice charlcd_dev = {
	.minor	= LCD_MINOR,
	.name	= "lcd",
	.fops	= &charlcd_fops,
};

static void charlcd_puts(struct charlcd *lcd, const char *s)
{
	const char *tmp = s;
	int count = strlen(s);

	for (; count-- > 0; tmp++) {
		if (!in_interrupt() && (((count + 1) & 0x1f) == 0))
			/*
			 * let's be a little nice with other processes
			 * that need some CPU
			 */
			schedule();

		charlcd_write_char(lcd, *tmp);
	}
}

/* initialize the LCD driver */
static int charlcd_init(struct charlcd *lcd)
{
	struct charlcd_priv *priv = to_priv(lcd);
	int ret;

	if (lcd->ops->backlight) {
		mutex_init(&priv->bl_tempo_lock);
		INIT_DELAYED_WORK(&priv->bl_work, charlcd_bl_off);
	}

	/*
	 * before this line, we must NOT send anything to the display.
	 * Since charlcd_init_display() needs to write data, we have to
	 * enable mark the LCD initialized just before.
	 */
	ret = charlcd_init_display(lcd);
	if (ret)
		return ret;

	/* display a short message */
#ifdef CONFIG_PANEL_CHANGE_MESSAGE
#ifdef CONFIG_PANEL_BOOT_MESSAGE
	charlcd_puts(lcd, "\x1b[Lc\x1b[Lb\x1b[L*" CONFIG_PANEL_BOOT_MESSAGE);
#endif
#else
	charlcd_puts(lcd, "\x1b[Lc\x1b[Lb\x1b[L*Linux-" UTS_RELEASE "\n");
#endif
	/* clear the display on the next device opening */
	priv->must_clear = true;
	charlcd_home(lcd);
	return 0;
}

struct charlcd *charlcd_alloc(unsigned int drvdata_size)
{
	struct charlcd_priv *priv;
	struct charlcd *lcd;

	priv = kzalloc(sizeof(*priv) + drvdata_size, GFP_KERNEL);
	if (!priv)
		return NULL;

	priv->esc_seq.len = -1;

	lcd = &priv->lcd;
	lcd->ifwidth = 8;
	lcd->bwidth = DEFAULT_LCD_BWIDTH;
	lcd->hwidth = DEFAULT_LCD_HWIDTH;
	lcd->drvdata = priv->drvdata;

	return lcd;
}
EXPORT_SYMBOL_GPL(charlcd_alloc);

static int panel_notify_sys(struct notifier_block *this, unsigned long code,
			    void *unused)
{
	struct charlcd *lcd = the_charlcd;

	switch (code) {
	case SYS_DOWN:
		charlcd_puts(lcd,
			     "\x0cReloading\nSystem...\x1b[Lc\x1b[Lb\x1b[L+");
		break;
	case SYS_HALT:
		charlcd_puts(lcd, "\x0cSystem Halted.\x1b[Lc\x1b[Lb\x1b[L+");
		break;
	case SYS_POWER_OFF:
		charlcd_puts(lcd, "\x0cPower off.\x1b[Lc\x1b[Lb\x1b[L+");
		break;
	default:
		break;
	}
	return NOTIFY_DONE;
}

static struct notifier_block panel_notifier = {
	panel_notify_sys,
	NULL,
	0
};

int charlcd_register(struct charlcd *lcd)
{
	int ret;

	ret = charlcd_init(lcd);
	if (ret)
		return ret;

	ret = misc_register(&charlcd_dev);
	if (ret)
		return ret;

	the_charlcd = lcd;
	register_reboot_notifier(&panel_notifier);
	return 0;
}
EXPORT_SYMBOL_GPL(charlcd_register);

int charlcd_unregister(struct charlcd *lcd)
{
	struct charlcd_priv *priv = to_priv(lcd);

	unregister_reboot_notifier(&panel_notifier);
	charlcd_puts(lcd, "\x0cLCD driver unloaded.\x1b[Lc\x1b[Lb\x1b[L-");
	misc_deregister(&charlcd_dev);
	the_charlcd = NULL;
	if (lcd->ops->backlight) {
		cancel_delayed_work_sync(&priv->bl_work);
		priv->lcd.ops->backlight(&priv->lcd, 0);
	}

	return 0;
}
EXPORT_SYMBOL_GPL(charlcd_unregister);

MODULE_LICENSE("GPL");