Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 884 insertions, 0 deletions

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
new file mode 100644
index 000000000..60e0b7726
--- /dev/null
+++ b/drivers/auxdisplay/charlcd.c
@@ -0,0 +1,884 @@
+// 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 (priv->esc_seq.buf[priv->esc_seq.len - 1] != ';')
+			break;
+
+		/* 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");