xref: /openbmc/linux/drivers/auxdisplay/charlcd.c (revision d2c43ff1)
1 /*
2  * Character LCD driver for Linux
3  *
4  * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
5  * Copyright (C) 2016-2017 Glider bvba
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License
9  * as published by the Free Software Foundation; either version
10  * 2 of the License, or (at your option) any later version.
11  */
12 
13 #include <linux/atomic.h>
14 #include <linux/delay.h>
15 #include <linux/fs.h>
16 #include <linux/miscdevice.h>
17 #include <linux/module.h>
18 #include <linux/notifier.h>
19 #include <linux/reboot.h>
20 #include <linux/slab.h>
21 #include <linux/uaccess.h>
22 #include <linux/workqueue.h>
23 
24 #include <generated/utsrelease.h>
25 
26 #include <misc/charlcd.h>
27 
28 #define LCD_MINOR		156
29 
30 #define DEFAULT_LCD_BWIDTH      40
31 #define DEFAULT_LCD_HWIDTH      64
32 
33 /* Keep the backlight on this many seconds for each flash */
34 #define LCD_BL_TEMPO_PERIOD	4
35 
36 #define LCD_FLAG_B		0x0004	/* Blink on */
37 #define LCD_FLAG_C		0x0008	/* Cursor on */
38 #define LCD_FLAG_D		0x0010	/* Display on */
39 #define LCD_FLAG_F		0x0020	/* Large font mode */
40 #define LCD_FLAG_N		0x0040	/* 2-rows mode */
41 #define LCD_FLAG_L		0x0080	/* Backlight enabled */
42 
43 /* LCD commands */
44 #define LCD_CMD_DISPLAY_CLEAR	0x01	/* Clear entire display */
45 
46 #define LCD_CMD_ENTRY_MODE	0x04	/* Set entry mode */
47 #define LCD_CMD_CURSOR_INC	0x02	/* Increment cursor */
48 
49 #define LCD_CMD_DISPLAY_CTRL	0x08	/* Display control */
50 #define LCD_CMD_DISPLAY_ON	0x04	/* Set display on */
51 #define LCD_CMD_CURSOR_ON	0x02	/* Set cursor on */
52 #define LCD_CMD_BLINK_ON	0x01	/* Set blink on */
53 
54 #define LCD_CMD_SHIFT		0x10	/* Shift cursor/display */
55 #define LCD_CMD_DISPLAY_SHIFT	0x08	/* Shift display instead of cursor */
56 #define LCD_CMD_SHIFT_RIGHT	0x04	/* Shift display/cursor to the right */
57 
58 #define LCD_CMD_FUNCTION_SET	0x20	/* Set function */
59 #define LCD_CMD_DATA_LEN_8BITS	0x10	/* Set data length to 8 bits */
60 #define LCD_CMD_TWO_LINES	0x08	/* Set to two display lines */
61 #define LCD_CMD_FONT_5X10_DOTS	0x04	/* Set char font to 5x10 dots */
62 
63 #define LCD_CMD_SET_CGRAM_ADDR	0x40	/* Set char generator RAM address */
64 
65 #define LCD_CMD_SET_DDRAM_ADDR	0x80	/* Set display data RAM address */
66 
67 #define LCD_ESCAPE_LEN		24	/* Max chars for LCD escape command */
68 #define LCD_ESCAPE_CHAR		27	/* Use char 27 for escape command */
69 
70 struct charlcd_priv {
71 	struct charlcd lcd;
72 
73 	struct delayed_work bl_work;
74 	struct mutex bl_tempo_lock;	/* Protects access to bl_tempo */
75 	bool bl_tempo;
76 
77 	bool must_clear;
78 
79 	/* contains the LCD config state */
80 	unsigned long int flags;
81 
82 	/* Contains the LCD X and Y offset */
83 	struct {
84 		unsigned long int x;
85 		unsigned long int y;
86 	} addr;
87 
88 	/* Current escape sequence and it's length or -1 if outside */
89 	struct {
90 		char buf[LCD_ESCAPE_LEN + 1];
91 		int len;
92 	} esc_seq;
93 
94 	unsigned long long drvdata[0];
95 };
96 
97 #define to_priv(p)	container_of(p, struct charlcd_priv, lcd)
98 
99 /* Device single-open policy control */
100 static atomic_t charlcd_available = ATOMIC_INIT(1);
101 
102 /* sleeps that many milliseconds with a reschedule */
103 static void long_sleep(int ms)
104 {
105 	if (in_interrupt())
106 		mdelay(ms);
107 	else
108 		schedule_timeout_interruptible(msecs_to_jiffies(ms));
109 }
110 
111 /* turn the backlight on or off */
112 static void charlcd_backlight(struct charlcd *lcd, int on)
113 {
114 	struct charlcd_priv *priv = to_priv(lcd);
115 
116 	if (!lcd->ops->backlight)
117 		return;
118 
119 	mutex_lock(&priv->bl_tempo_lock);
120 	if (!priv->bl_tempo)
121 		lcd->ops->backlight(lcd, on);
122 	mutex_unlock(&priv->bl_tempo_lock);
123 }
124 
125 static void charlcd_bl_off(struct work_struct *work)
126 {
127 	struct delayed_work *dwork = to_delayed_work(work);
128 	struct charlcd_priv *priv =
129 		container_of(dwork, struct charlcd_priv, bl_work);
130 
131 	mutex_lock(&priv->bl_tempo_lock);
132 	if (priv->bl_tempo) {
133 		priv->bl_tempo = false;
134 		if (!(priv->flags & LCD_FLAG_L))
135 			priv->lcd.ops->backlight(&priv->lcd, 0);
136 	}
137 	mutex_unlock(&priv->bl_tempo_lock);
138 }
139 
140 /* turn the backlight on for a little while */
141 void charlcd_poke(struct charlcd *lcd)
142 {
143 	struct charlcd_priv *priv = to_priv(lcd);
144 
145 	if (!lcd->ops->backlight)
146 		return;
147 
148 	cancel_delayed_work_sync(&priv->bl_work);
149 
150 	mutex_lock(&priv->bl_tempo_lock);
151 	if (!priv->bl_tempo && !(priv->flags & LCD_FLAG_L))
152 		lcd->ops->backlight(lcd, 1);
153 	priv->bl_tempo = true;
154 	schedule_delayed_work(&priv->bl_work, LCD_BL_TEMPO_PERIOD * HZ);
155 	mutex_unlock(&priv->bl_tempo_lock);
156 }
157 EXPORT_SYMBOL_GPL(charlcd_poke);
158 
159 static void charlcd_gotoxy(struct charlcd *lcd)
160 {
161 	struct charlcd_priv *priv = to_priv(lcd);
162 	unsigned int addr;
163 
164 	/*
165 	 * we force the cursor to stay at the end of the
166 	 * line if it wants to go farther
167 	 */
168 	addr = priv->addr.x < lcd->bwidth ? priv->addr.x & (lcd->hwidth - 1)
169 					  : lcd->bwidth - 1;
170 	if (priv->addr.y & 1)
171 		addr += lcd->hwidth;
172 	if (priv->addr.y & 2)
173 		addr += lcd->bwidth;
174 	lcd->ops->write_cmd(lcd, LCD_CMD_SET_DDRAM_ADDR | addr);
175 }
176 
177 static void charlcd_home(struct charlcd *lcd)
178 {
179 	struct charlcd_priv *priv = to_priv(lcd);
180 
181 	priv->addr.x = 0;
182 	priv->addr.y = 0;
183 	charlcd_gotoxy(lcd);
184 }
185 
186 static void charlcd_print(struct charlcd *lcd, char c)
187 {
188 	struct charlcd_priv *priv = to_priv(lcd);
189 
190 	if (priv->addr.x < lcd->bwidth) {
191 		if (lcd->char_conv)
192 			c = lcd->char_conv[(unsigned char)c];
193 		lcd->ops->write_data(lcd, c);
194 		priv->addr.x++;
195 	}
196 	/* prevents the cursor from wrapping onto the next line */
197 	if (priv->addr.x == lcd->bwidth)
198 		charlcd_gotoxy(lcd);
199 }
200 
201 static void charlcd_clear_fast(struct charlcd *lcd)
202 {
203 	int pos;
204 
205 	charlcd_home(lcd);
206 
207 	if (lcd->ops->clear_fast)
208 		lcd->ops->clear_fast(lcd);
209 	else
210 		for (pos = 0; pos < min(2, lcd->height) * lcd->hwidth; pos++)
211 			lcd->ops->write_data(lcd, ' ');
212 
213 	charlcd_home(lcd);
214 }
215 
216 /* clears the display and resets X/Y */
217 static void charlcd_clear_display(struct charlcd *lcd)
218 {
219 	struct charlcd_priv *priv = to_priv(lcd);
220 
221 	lcd->ops->write_cmd(lcd, LCD_CMD_DISPLAY_CLEAR);
222 	priv->addr.x = 0;
223 	priv->addr.y = 0;
224 	/* we must wait a few milliseconds (15) */
225 	long_sleep(15);
226 }
227 
228 static int charlcd_init_display(struct charlcd *lcd)
229 {
230 	void (*write_cmd_raw)(struct charlcd *lcd, int cmd);
231 	struct charlcd_priv *priv = to_priv(lcd);
232 	u8 init;
233 
234 	if (lcd->ifwidth != 4 && lcd->ifwidth != 8)
235 		return -EINVAL;
236 
237 	priv->flags = ((lcd->height > 1) ? LCD_FLAG_N : 0) | LCD_FLAG_D |
238 		      LCD_FLAG_C | LCD_FLAG_B;
239 
240 	long_sleep(20);		/* wait 20 ms after power-up for the paranoid */
241 
242 	/*
243 	 * 8-bit mode, 1 line, small fonts; let's do it 3 times, to make sure
244 	 * the LCD is in 8-bit mode afterwards
245 	 */
246 	init = LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS;
247 	if (lcd->ifwidth == 4) {
248 		init >>= 4;
249 		write_cmd_raw = lcd->ops->write_cmd_raw4;
250 	} else {
251 		write_cmd_raw = lcd->ops->write_cmd;
252 	}
253 	write_cmd_raw(lcd, init);
254 	long_sleep(10);
255 	write_cmd_raw(lcd, init);
256 	long_sleep(10);
257 	write_cmd_raw(lcd, init);
258 	long_sleep(10);
259 
260 	if (lcd->ifwidth == 4) {
261 		/* Switch to 4-bit mode, 1 line, small fonts */
262 		lcd->ops->write_cmd_raw4(lcd, LCD_CMD_FUNCTION_SET >> 4);
263 		long_sleep(10);
264 	}
265 
266 	/* set font height and lines number */
267 	lcd->ops->write_cmd(lcd,
268 		LCD_CMD_FUNCTION_SET |
269 		((lcd->ifwidth == 8) ? LCD_CMD_DATA_LEN_8BITS : 0) |
270 		((priv->flags & LCD_FLAG_F) ? LCD_CMD_FONT_5X10_DOTS : 0) |
271 		((priv->flags & LCD_FLAG_N) ? LCD_CMD_TWO_LINES : 0));
272 	long_sleep(10);
273 
274 	/* display off, cursor off, blink off */
275 	lcd->ops->write_cmd(lcd, LCD_CMD_DISPLAY_CTRL);
276 	long_sleep(10);
277 
278 	lcd->ops->write_cmd(lcd,
279 		LCD_CMD_DISPLAY_CTRL |	/* set display mode */
280 		((priv->flags & LCD_FLAG_D) ? LCD_CMD_DISPLAY_ON : 0) |
281 		((priv->flags & LCD_FLAG_C) ? LCD_CMD_CURSOR_ON : 0) |
282 		((priv->flags & LCD_FLAG_B) ? LCD_CMD_BLINK_ON : 0));
283 
284 	charlcd_backlight(lcd, (priv->flags & LCD_FLAG_L) ? 1 : 0);
285 
286 	long_sleep(10);
287 
288 	/* entry mode set : increment, cursor shifting */
289 	lcd->ops->write_cmd(lcd, LCD_CMD_ENTRY_MODE | LCD_CMD_CURSOR_INC);
290 
291 	charlcd_clear_display(lcd);
292 	return 0;
293 }
294 
295 /*
296  * These are the file operation function for user access to /dev/lcd
297  * This function can also be called from inside the kernel, by
298  * setting file and ppos to NULL.
299  *
300  */
301 
302 static inline int handle_lcd_special_code(struct charlcd *lcd)
303 {
304 	struct charlcd_priv *priv = to_priv(lcd);
305 
306 	/* LCD special codes */
307 
308 	int processed = 0;
309 
310 	char *esc = priv->esc_seq.buf + 2;
311 	int oldflags = priv->flags;
312 
313 	/* check for display mode flags */
314 	switch (*esc) {
315 	case 'D':	/* Display ON */
316 		priv->flags |= LCD_FLAG_D;
317 		processed = 1;
318 		break;
319 	case 'd':	/* Display OFF */
320 		priv->flags &= ~LCD_FLAG_D;
321 		processed = 1;
322 		break;
323 	case 'C':	/* Cursor ON */
324 		priv->flags |= LCD_FLAG_C;
325 		processed = 1;
326 		break;
327 	case 'c':	/* Cursor OFF */
328 		priv->flags &= ~LCD_FLAG_C;
329 		processed = 1;
330 		break;
331 	case 'B':	/* Blink ON */
332 		priv->flags |= LCD_FLAG_B;
333 		processed = 1;
334 		break;
335 	case 'b':	/* Blink OFF */
336 		priv->flags &= ~LCD_FLAG_B;
337 		processed = 1;
338 		break;
339 	case '+':	/* Back light ON */
340 		priv->flags |= LCD_FLAG_L;
341 		processed = 1;
342 		break;
343 	case '-':	/* Back light OFF */
344 		priv->flags &= ~LCD_FLAG_L;
345 		processed = 1;
346 		break;
347 	case '*':	/* Flash back light */
348 		charlcd_poke(lcd);
349 		processed = 1;
350 		break;
351 	case 'f':	/* Small Font */
352 		priv->flags &= ~LCD_FLAG_F;
353 		processed = 1;
354 		break;
355 	case 'F':	/* Large Font */
356 		priv->flags |= LCD_FLAG_F;
357 		processed = 1;
358 		break;
359 	case 'n':	/* One Line */
360 		priv->flags &= ~LCD_FLAG_N;
361 		processed = 1;
362 		break;
363 	case 'N':	/* Two Lines */
364 		priv->flags |= LCD_FLAG_N;
365 		break;
366 	case 'l':	/* Shift Cursor Left */
367 		if (priv->addr.x > 0) {
368 			/* back one char if not at end of line */
369 			if (priv->addr.x < lcd->bwidth)
370 				lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT);
371 			priv->addr.x--;
372 		}
373 		processed = 1;
374 		break;
375 	case 'r':	/* shift cursor right */
376 		if (priv->addr.x < lcd->width) {
377 			/* allow the cursor to pass the end of the line */
378 			if (priv->addr.x < (lcd->bwidth - 1))
379 				lcd->ops->write_cmd(lcd,
380 					LCD_CMD_SHIFT | LCD_CMD_SHIFT_RIGHT);
381 			priv->addr.x++;
382 		}
383 		processed = 1;
384 		break;
385 	case 'L':	/* shift display left */
386 		lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT | LCD_CMD_DISPLAY_SHIFT);
387 		processed = 1;
388 		break;
389 	case 'R':	/* shift display right */
390 		lcd->ops->write_cmd(lcd,
391 				    LCD_CMD_SHIFT | LCD_CMD_DISPLAY_SHIFT |
392 				    LCD_CMD_SHIFT_RIGHT);
393 		processed = 1;
394 		break;
395 	case 'k': {	/* kill end of line */
396 		int x;
397 
398 		for (x = priv->addr.x; x < lcd->bwidth; x++)
399 			lcd->ops->write_data(lcd, ' ');
400 
401 		/* restore cursor position */
402 		charlcd_gotoxy(lcd);
403 		processed = 1;
404 		break;
405 	}
406 	case 'I':	/* reinitialize display */
407 		charlcd_init_display(lcd);
408 		processed = 1;
409 		break;
410 	case 'G': {
411 		/* Generator : LGcxxxxx...xx; must have <c> between '0'
412 		 * and '7', representing the numerical ASCII code of the
413 		 * redefined character, and <xx...xx> a sequence of 16
414 		 * hex digits representing 8 bytes for each character.
415 		 * Most LCDs will only use 5 lower bits of the 7 first
416 		 * bytes.
417 		 */
418 
419 		unsigned char cgbytes[8];
420 		unsigned char cgaddr;
421 		int cgoffset;
422 		int shift;
423 		char value;
424 		int addr;
425 
426 		if (!strchr(esc, ';'))
427 			break;
428 
429 		esc++;
430 
431 		cgaddr = *(esc++) - '0';
432 		if (cgaddr > 7) {
433 			processed = 1;
434 			break;
435 		}
436 
437 		cgoffset = 0;
438 		shift = 0;
439 		value = 0;
440 		while (*esc && cgoffset < 8) {
441 			shift ^= 4;
442 			if (*esc >= '0' && *esc <= '9') {
443 				value |= (*esc - '0') << shift;
444 			} else if (*esc >= 'A' && *esc <= 'Z') {
445 				value |= (*esc - 'A' + 10) << shift;
446 			} else if (*esc >= 'a' && *esc <= 'z') {
447 				value |= (*esc - 'a' + 10) << shift;
448 			} else {
449 				esc++;
450 				continue;
451 			}
452 
453 			if (shift == 0) {
454 				cgbytes[cgoffset++] = value;
455 				value = 0;
456 			}
457 
458 			esc++;
459 		}
460 
461 		lcd->ops->write_cmd(lcd, LCD_CMD_SET_CGRAM_ADDR | (cgaddr * 8));
462 		for (addr = 0; addr < cgoffset; addr++)
463 			lcd->ops->write_data(lcd, cgbytes[addr]);
464 
465 		/* ensures that we stop writing to CGRAM */
466 		charlcd_gotoxy(lcd);
467 		processed = 1;
468 		break;
469 	}
470 	case 'x':	/* gotoxy : LxXXX[yYYY]; */
471 	case 'y':	/* gotoxy : LyYYY[xXXX]; */
472 		if (!strchr(esc, ';'))
473 			break;
474 
475 		while (*esc) {
476 			if (*esc == 'x') {
477 				esc++;
478 				if (kstrtoul(esc, 10, &priv->addr.x) < 0)
479 					break;
480 			} else if (*esc == 'y') {
481 				esc++;
482 				if (kstrtoul(esc, 10, &priv->addr.y) < 0)
483 					break;
484 			} else {
485 				break;
486 			}
487 		}
488 
489 		charlcd_gotoxy(lcd);
490 		processed = 1;
491 		break;
492 	}
493 
494 	/* TODO: This indent party here got ugly, clean it! */
495 	/* Check whether one flag was changed */
496 	if (oldflags == priv->flags)
497 		return processed;
498 
499 	/* check whether one of B,C,D flags were changed */
500 	if ((oldflags ^ priv->flags) &
501 	    (LCD_FLAG_B | LCD_FLAG_C | LCD_FLAG_D))
502 		/* set display mode */
503 		lcd->ops->write_cmd(lcd,
504 			LCD_CMD_DISPLAY_CTRL |
505 			((priv->flags & LCD_FLAG_D) ? LCD_CMD_DISPLAY_ON : 0) |
506 			((priv->flags & LCD_FLAG_C) ? LCD_CMD_CURSOR_ON : 0) |
507 			((priv->flags & LCD_FLAG_B) ? LCD_CMD_BLINK_ON : 0));
508 	/* check whether one of F,N flags was changed */
509 	else if ((oldflags ^ priv->flags) & (LCD_FLAG_F | LCD_FLAG_N))
510 		lcd->ops->write_cmd(lcd,
511 			LCD_CMD_FUNCTION_SET |
512 			((lcd->ifwidth == 8) ? LCD_CMD_DATA_LEN_8BITS : 0) |
513 			((priv->flags & LCD_FLAG_F) ? LCD_CMD_FONT_5X10_DOTS : 0) |
514 			((priv->flags & LCD_FLAG_N) ? LCD_CMD_TWO_LINES : 0));
515 	/* check whether L flag was changed */
516 	else if ((oldflags ^ priv->flags) & LCD_FLAG_L)
517 		charlcd_backlight(lcd, !!(priv->flags & LCD_FLAG_L));
518 
519 	return processed;
520 }
521 
522 static void charlcd_write_char(struct charlcd *lcd, char c)
523 {
524 	struct charlcd_priv *priv = to_priv(lcd);
525 
526 	/* first, we'll test if we're in escape mode */
527 	if ((c != '\n') && priv->esc_seq.len >= 0) {
528 		/* yes, let's add this char to the buffer */
529 		priv->esc_seq.buf[priv->esc_seq.len++] = c;
530 		priv->esc_seq.buf[priv->esc_seq.len] = 0;
531 	} else {
532 		/* aborts any previous escape sequence */
533 		priv->esc_seq.len = -1;
534 
535 		switch (c) {
536 		case LCD_ESCAPE_CHAR:
537 			/* start of an escape sequence */
538 			priv->esc_seq.len = 0;
539 			priv->esc_seq.buf[priv->esc_seq.len] = 0;
540 			break;
541 		case '\b':
542 			/* go back one char and clear it */
543 			if (priv->addr.x > 0) {
544 				/*
545 				 * check if we're not at the
546 				 * end of the line
547 				 */
548 				if (priv->addr.x < lcd->bwidth)
549 					/* back one char */
550 					lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT);
551 				priv->addr.x--;
552 			}
553 			/* replace with a space */
554 			lcd->ops->write_data(lcd, ' ');
555 			/* back one char again */
556 			lcd->ops->write_cmd(lcd, LCD_CMD_SHIFT);
557 			break;
558 		case '\014':
559 			/* quickly clear the display */
560 			charlcd_clear_fast(lcd);
561 			break;
562 		case '\n':
563 			/*
564 			 * flush the remainder of the current line and
565 			 * go to the beginning of the next line
566 			 */
567 			for (; priv->addr.x < lcd->bwidth; priv->addr.x++)
568 				lcd->ops->write_data(lcd, ' ');
569 			priv->addr.x = 0;
570 			priv->addr.y = (priv->addr.y + 1) % lcd->height;
571 			charlcd_gotoxy(lcd);
572 			break;
573 		case '\r':
574 			/* go to the beginning of the same line */
575 			priv->addr.x = 0;
576 			charlcd_gotoxy(lcd);
577 			break;
578 		case '\t':
579 			/* print a space instead of the tab */
580 			charlcd_print(lcd, ' ');
581 			break;
582 		default:
583 			/* simply print this char */
584 			charlcd_print(lcd, c);
585 			break;
586 		}
587 	}
588 
589 	/*
590 	 * now we'll see if we're in an escape mode and if the current
591 	 * escape sequence can be understood.
592 	 */
593 	if (priv->esc_seq.len >= 2) {
594 		int processed = 0;
595 
596 		if (!strcmp(priv->esc_seq.buf, "[2J")) {
597 			/* clear the display */
598 			charlcd_clear_fast(lcd);
599 			processed = 1;
600 		} else if (!strcmp(priv->esc_seq.buf, "[H")) {
601 			/* cursor to home */
602 			charlcd_home(lcd);
603 			processed = 1;
604 		}
605 		/* codes starting with ^[[L */
606 		else if ((priv->esc_seq.len >= 3) &&
607 			 (priv->esc_seq.buf[0] == '[') &&
608 			 (priv->esc_seq.buf[1] == 'L')) {
609 			processed = handle_lcd_special_code(lcd);
610 		}
611 
612 		/* LCD special escape codes */
613 		/*
614 		 * flush the escape sequence if it's been processed
615 		 * or if it is getting too long.
616 		 */
617 		if (processed || (priv->esc_seq.len >= LCD_ESCAPE_LEN))
618 			priv->esc_seq.len = -1;
619 	} /* escape codes */
620 }
621 
622 static struct charlcd *the_charlcd;
623 
624 static ssize_t charlcd_write(struct file *file, const char __user *buf,
625 			     size_t count, loff_t *ppos)
626 {
627 	const char __user *tmp = buf;
628 	char c;
629 
630 	for (; count-- > 0; (*ppos)++, tmp++) {
631 		if (!in_interrupt() && (((count + 1) & 0x1f) == 0))
632 			/*
633 			 * let's be a little nice with other processes
634 			 * that need some CPU
635 			 */
636 			schedule();
637 
638 		if (get_user(c, tmp))
639 			return -EFAULT;
640 
641 		charlcd_write_char(the_charlcd, c);
642 	}
643 
644 	return tmp - buf;
645 }
646 
647 static int charlcd_open(struct inode *inode, struct file *file)
648 {
649 	struct charlcd_priv *priv = to_priv(the_charlcd);
650 
651 	if (!atomic_dec_and_test(&charlcd_available))
652 		return -EBUSY;	/* open only once at a time */
653 
654 	if (file->f_mode & FMODE_READ)	/* device is write-only */
655 		return -EPERM;
656 
657 	if (priv->must_clear) {
658 		charlcd_clear_display(&priv->lcd);
659 		priv->must_clear = false;
660 	}
661 	return nonseekable_open(inode, file);
662 }
663 
664 static int charlcd_release(struct inode *inode, struct file *file)
665 {
666 	atomic_inc(&charlcd_available);
667 	return 0;
668 }
669 
670 static const struct file_operations charlcd_fops = {
671 	.write   = charlcd_write,
672 	.open    = charlcd_open,
673 	.release = charlcd_release,
674 	.llseek  = no_llseek,
675 };
676 
677 static struct miscdevice charlcd_dev = {
678 	.minor	= LCD_MINOR,
679 	.name	= "lcd",
680 	.fops	= &charlcd_fops,
681 };
682 
683 static void charlcd_puts(struct charlcd *lcd, const char *s)
684 {
685 	const char *tmp = s;
686 	int count = strlen(s);
687 
688 	for (; count-- > 0; tmp++) {
689 		if (!in_interrupt() && (((count + 1) & 0x1f) == 0))
690 			/*
691 			 * let's be a little nice with other processes
692 			 * that need some CPU
693 			 */
694 			schedule();
695 
696 		charlcd_write_char(lcd, *tmp);
697 	}
698 }
699 
700 /* initialize the LCD driver */
701 static int charlcd_init(struct charlcd *lcd)
702 {
703 	struct charlcd_priv *priv = to_priv(lcd);
704 	int ret;
705 
706 	if (lcd->ops->backlight) {
707 		mutex_init(&priv->bl_tempo_lock);
708 		INIT_DELAYED_WORK(&priv->bl_work, charlcd_bl_off);
709 	}
710 
711 	/*
712 	 * before this line, we must NOT send anything to the display.
713 	 * Since charlcd_init_display() needs to write data, we have to
714 	 * enable mark the LCD initialized just before.
715 	 */
716 	ret = charlcd_init_display(lcd);
717 	if (ret)
718 		return ret;
719 
720 	/* display a short message */
721 #ifdef CONFIG_PANEL_CHANGE_MESSAGE
722 #ifdef CONFIG_PANEL_BOOT_MESSAGE
723 	charlcd_puts(lcd, "\x1b[Lc\x1b[Lb\x1b[L*" CONFIG_PANEL_BOOT_MESSAGE);
724 #endif
725 #else
726 	charlcd_puts(lcd, "\x1b[Lc\x1b[Lb\x1b[L*Linux-" UTS_RELEASE "\n");
727 #endif
728 	/* clear the display on the next device opening */
729 	priv->must_clear = true;
730 	charlcd_home(lcd);
731 	return 0;
732 }
733 
734 struct charlcd *charlcd_alloc(unsigned int drvdata_size)
735 {
736 	struct charlcd_priv *priv;
737 	struct charlcd *lcd;
738 
739 	priv = kzalloc(sizeof(*priv) + drvdata_size, GFP_KERNEL);
740 	if (!priv)
741 		return NULL;
742 
743 	priv->esc_seq.len = -1;
744 
745 	lcd = &priv->lcd;
746 	lcd->ifwidth = 8;
747 	lcd->bwidth = DEFAULT_LCD_BWIDTH;
748 	lcd->hwidth = DEFAULT_LCD_HWIDTH;
749 	lcd->drvdata = priv->drvdata;
750 
751 	return lcd;
752 }
753 EXPORT_SYMBOL_GPL(charlcd_alloc);
754 
755 static int panel_notify_sys(struct notifier_block *this, unsigned long code,
756 			    void *unused)
757 {
758 	struct charlcd *lcd = the_charlcd;
759 
760 	switch (code) {
761 	case SYS_DOWN:
762 		charlcd_puts(lcd,
763 			     "\x0cReloading\nSystem...\x1b[Lc\x1b[Lb\x1b[L+");
764 		break;
765 	case SYS_HALT:
766 		charlcd_puts(lcd, "\x0cSystem Halted.\x1b[Lc\x1b[Lb\x1b[L+");
767 		break;
768 	case SYS_POWER_OFF:
769 		charlcd_puts(lcd, "\x0cPower off.\x1b[Lc\x1b[Lb\x1b[L+");
770 		break;
771 	default:
772 		break;
773 	}
774 	return NOTIFY_DONE;
775 }
776 
777 static struct notifier_block panel_notifier = {
778 	panel_notify_sys,
779 	NULL,
780 	0
781 };
782 
783 int charlcd_register(struct charlcd *lcd)
784 {
785 	int ret;
786 
787 	ret = charlcd_init(lcd);
788 	if (ret)
789 		return ret;
790 
791 	ret = misc_register(&charlcd_dev);
792 	if (ret)
793 		return ret;
794 
795 	the_charlcd = lcd;
796 	register_reboot_notifier(&panel_notifier);
797 	return 0;
798 }
799 EXPORT_SYMBOL_GPL(charlcd_register);
800 
801 int charlcd_unregister(struct charlcd *lcd)
802 {
803 	struct charlcd_priv *priv = to_priv(lcd);
804 
805 	unregister_reboot_notifier(&panel_notifier);
806 	charlcd_puts(lcd, "\x0cLCD driver unloaded.\x1b[Lc\x1b[Lb\x1b[L-");
807 	misc_deregister(&charlcd_dev);
808 	the_charlcd = NULL;
809 	if (lcd->ops->backlight) {
810 		cancel_delayed_work_sync(&priv->bl_work);
811 		priv->lcd.ops->backlight(&priv->lcd, 0);
812 	}
813 
814 	return 0;
815 }
816 EXPORT_SYMBOL_GPL(charlcd_unregister);
817 
818 MODULE_LICENSE("GPL");
819