auxdisplay: charlcd: Extract character LCD core from misc/panel

Extract the character LCD core from the Parallel port LCD/Keypad Panel
driver in the misc subsystem, and convert it into a subdriver in the
auxdisplay subsystem.  This allows the character LCD core to be used by
other drivers later.

Compilation is controlled by its own Kconfig symbol CHARLCD, which is to
be selected by its users, but can be enabled manually for
compile-testing.

All functions changed their prefix from "lcd_" to "charlcd_", and gained
a "struct charlcd *" parameter to operate on a specific instance.
While the driver API thus is ready to support multiple instances, the
current limitation of a single display (/dev/lcd has a single misc minor
assigned) is retained.

No functional changes intended.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 794 insertions, 0 deletions

diff --git a/drivers/auxdisplay/Kconfig b/drivers/auxdisplay/Kconfig
index 8a8e403..b468638 100644
--- a/drivers/auxdisplay/Kconfig
+++ b/drivers/auxdisplay/Kconfig
@@ -13,6 +13,9 @@ menuconfig AUXDISPLAY
 
 	  If you say N, all options in this submenu will be skipped and disabled.
 
+config CHARLCD
+	tristate "Character LCD core support" if COMPILE_TEST
+
 if AUXDISPLAY
 
 config KS0108
diff --git a/drivers/auxdisplay/Makefile b/drivers/auxdisplay/Makefile
index cb3dd84..f56f45d 100644
--- a/drivers/auxdisplay/Makefile
+++ b/drivers/auxdisplay/Makefile
@@ -2,6 +2,7 @@
 # Makefile for the kernel auxiliary displays device drivers.
 #
 
+obj-$(CONFIG_CHARLCD)		+= charlcd.o
 obj-$(CONFIG_KS0108)		+= ks0108.o
 obj-$(CONFIG_CFAG12864B)	+= cfag12864b.o cfag12864bfb.o
 obj-$(CONFIG_IMG_ASCII_LCD)	+= img-ascii-lcd.o
diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
new file mode 100644
index 0000000..930ffb2
--- /dev/null
+++ b/drivers/auxdisplay/charlcd.c
@@ -0,0 +1,790 @@
+/*
+ * Character LCD driver for Linux
+ *
+ * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
+ * Copyright (C) 2016-2017 Glider bvba
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/atomic.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)
+{
+	if (in_interrupt())
+		mdelay(ms);
+	else
+		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);
+
+	lcd->ops->write_cmd(lcd,
+		LCD_CMD_SET_DDRAM_ADDR | (priv->addr.y ? lcd->hwidth : 0) |
+		/*
+		 * we force the cursor to stay at the end of the
+		 * line if it wants to go farther
+		 */
+		((priv->addr.x < lcd->bwidth) ? priv->addr.x & (lcd->hwidth - 1)
+					      : lcd->bwidth - 1));
+}
+
+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 < 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)
+{
+	struct charlcd_priv *priv = to_priv(lcd);
+
+	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 */
+
+	/* 8bits, 1 line, small fonts; let's do it 3 times */
+	lcd->ops->write_cmd(lcd, LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS);
+	long_sleep(10);
+	lcd->ops->write_cmd(lcd, LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS);
+	long_sleep(10);
+	lcd->ops->write_cmd(lcd, LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS);
+	long_sleep(10);
+
+	/* set font height and lines number */
+	lcd->ops->write_cmd(lcd,
+		LCD_CMD_FUNCTION_SET | LCD_CMD_DATA_LEN_8BITS |
+		((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;
+}
+
+/*
+ * 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;
+		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 <= 'Z') {
+				value |= (*esc - 'A' + 10) << shift;
+			} else if (*esc >= 'a' && *esc <= 'z') {
+				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 (!strchr(esc, ';'))
+			break;
+
+		while (*esc) {
+			if (*esc == 'x') {
+				esc++;
+				if (kstrtoul(esc, 10, &priv->addr.x) < 0)
+					break;
+			} else if (*esc == 'y') {
+				esc++;
+				if (kstrtoul(esc, 10, &priv->addr.y) < 0)
+					break;
+			} else {
+				break;
+			}
+		}
+
+		charlcd_gotoxy(lcd);
+		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_CMD_DATA_LEN_8BITS |
+			((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 '\014':
+			/* 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);
+
+	if (!atomic_dec_and_test(&charlcd_available))
+		return -EBUSY;	/* open only once at a time */
+
+	if (file->f_mode & FMODE_READ)	/* device is write-only */
+		return -EPERM;
+
+	if (priv->must_clear) {
+		charlcd_clear_display(&priv->lcd);
+		priv->must_clear = false;
+	}
+	return nonseekable_open(inode, file);
+}
+
+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->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");