/*
 * 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);
        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;
}

/*
 * 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->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 '\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->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");