charlcd.c
// 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/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 "charlcd.h"
/* Keep the backlight on this many seconds for each flash */
#define LCD_BL_TEMPO_PERIOD 4
#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;
/* 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[];
};
#define charlcd_to_priv(p) container_of(p, struct charlcd_priv, lcd)
/* Device single-open policy control */
static atomic_t charlcd_available = ATOMIC_INIT(1);
/* turn the backlight on or off */
void charlcd_backlight(struct charlcd *lcd, enum charlcd_onoff on)
{
struct charlcd_priv *priv = charlcd_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);
}
EXPORT_SYMBOL_GPL(charlcd_backlight);
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, CHARLCD_OFF);
}
mutex_unlock(&priv->bl_tempo_lock);
}
/* turn the backlight on for a little while */
void charlcd_poke(struct charlcd *lcd)
{
struct charlcd_priv *priv = charlcd_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, CHARLCD_ON);
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_home(struct charlcd *lcd)
{
lcd->addr.x = 0;
lcd->addr.y = 0;
lcd->ops->home(lcd);
}
static void charlcd_print(struct charlcd *lcd, char c)
{
if (lcd->addr.x >= lcd->width)
return;
if (lcd->char_conv)
c = lcd->char_conv[(unsigned char)c];
if (!lcd->ops->print(lcd, c))
lcd->addr.x++;
/* prevents the cursor from wrapping onto the next line */
if (lcd->addr.x == lcd->width)
lcd->ops->gotoxy(lcd, lcd->addr.x - 1, lcd->addr.y);
}
static void charlcd_clear_display(struct charlcd *lcd)
{
lcd->ops->clear_display(lcd);
lcd->addr.x = 0;
lcd->addr.y = 0;
}
/*
* 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;
char *p;
for (;;) {
if (!*s)
return false;
if (*s == ';')
break;
if (*s == 'x') {
new_x = simple_strtoul(s + 1, &p, 10);
if (p == s + 1)
return false;
s = p;
} else if (*s == 'y') {
new_y = simple_strtoul(s + 1, &p, 10);
if (p == s + 1)
return false;
s = p;
} 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 = charlcd_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;
if (priv->flags != oldflags)
lcd->ops->display(lcd, CHARLCD_ON);
processed = 1;
break;
case 'd': /* Display OFF */
priv->flags &= ~LCD_FLAG_D;
if (priv->flags != oldflags)
lcd->ops->display(lcd, CHARLCD_OFF);
processed = 1;
break;
case 'C': /* Cursor ON */
priv->flags |= LCD_FLAG_C;
if (priv->flags != oldflags)
lcd->ops->cursor(lcd, CHARLCD_ON);
processed = 1;
break;
case 'c': /* Cursor OFF */
priv->flags &= ~LCD_FLAG_C;
if (priv->flags != oldflags)
lcd->ops->cursor(lcd, CHARLCD_OFF);
processed = 1;
break;
case 'B': /* Blink ON */
priv->flags |= LCD_FLAG_B;
if (priv->flags != oldflags)
lcd->ops->blink(lcd, CHARLCD_ON);
processed = 1;
break;
case 'b': /* Blink OFF */
priv->flags &= ~LCD_FLAG_B;
if (priv->flags != oldflags)
lcd->ops->blink(lcd, CHARLCD_OFF);
processed = 1;
break;
case '+': /* Back light ON */
priv->flags |= LCD_FLAG_L;
if (priv->flags != oldflags)
charlcd_backlight(lcd, CHARLCD_ON);
processed = 1;
break;
case '-': /* Back light OFF */
priv->flags &= ~LCD_FLAG_L;
if (priv->flags != oldflags)
charlcd_backlight(lcd, CHARLCD_OFF);
processed = 1;
break;
case '*': /* Flash back light */
charlcd_poke(lcd);
processed = 1;
break;
case 'f': /* Small Font */
priv->flags &= ~LCD_FLAG_F;
if (priv->flags != oldflags)
lcd->ops->fontsize(lcd, CHARLCD_FONTSIZE_SMALL);
processed = 1;
break;
case 'F': /* Large Font */
priv->flags |= LCD_FLAG_F;
if (priv->flags != oldflags)
lcd->ops->fontsize(lcd, CHARLCD_FONTSIZE_LARGE);
processed = 1;
break;
case 'n': /* One Line */
priv->flags &= ~LCD_FLAG_N;
if (priv->flags != oldflags)
lcd->ops->lines(lcd, CHARLCD_LINES_1);
processed = 1;
break;
case 'N': /* Two Lines */
priv->flags |= LCD_FLAG_N;
if (priv->flags != oldflags)
lcd->ops->lines(lcd, CHARLCD_LINES_2);
processed = 1;
break;
case 'l': /* Shift Cursor Left */
if (lcd->addr.x > 0) {
if (!lcd->ops->shift_cursor(lcd, CHARLCD_SHIFT_LEFT))
lcd->addr.x--;
}
processed = 1;
break;
case 'r': /* shift cursor right */
if (lcd->addr.x < lcd->width) {
if (!lcd->ops->shift_cursor(lcd, CHARLCD_SHIFT_RIGHT))
lcd->addr.x++;
}
processed = 1;
break;
case 'L': /* shift display left */
lcd->ops->shift_display(lcd, CHARLCD_SHIFT_LEFT);
processed = 1;
break;
case 'R': /* shift display right */
lcd->ops->shift_display(lcd, CHARLCD_SHIFT_RIGHT);
processed = 1;
break;
case 'k': { /* kill end of line */
int x, xs, ys;
xs = lcd->addr.x;
ys = lcd->addr.y;
for (x = lcd->addr.x; x < lcd->width; x++)
lcd->ops->print(lcd, ' ');
/* restore cursor position */
lcd->addr.x = xs;
lcd->addr.y = ys;
lcd->ops->gotoxy(lcd, lcd->addr.x, lcd->addr.y);
processed = 1;
break;
}
case 'I': /* reinitialize display */
lcd->ops->init_display(lcd);
priv->flags = ((lcd->height > 1) ? LCD_FLAG_N : 0) | LCD_FLAG_D |
LCD_FLAG_C | LCD_FLAG_B;
processed = 1;
break;
case 'G':
if (lcd->ops->redefine_char)
processed = lcd->ops->redefine_char(lcd, esc);
else
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, &lcd->addr.x, &lcd->addr.y))
lcd->ops->gotoxy(lcd, lcd->addr.x, lcd->addr.y);
/* Regardless of its validity, mark as processed */
processed = 1;
break;
}
return processed;
}
static void charlcd_write_char(struct charlcd *lcd, char c)
{
struct charlcd_priv *priv = charlcd_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 (lcd->addr.x > 0) {
/* back one char */
if (!lcd->ops->shift_cursor(lcd,
CHARLCD_SHIFT_LEFT))
lcd->addr.x--;
}
/* replace with a space */
charlcd_print(lcd, ' ');
/* back one char again */
if (!lcd->ops->shift_cursor(lcd, CHARLCD_SHIFT_LEFT))
lcd->addr.x--;
break;
case '\f':
/* quickly clear the display */
charlcd_clear_display(lcd);
break;
case '\n':
/*
* flush the remainder of the current line and
* go to the beginning of the next line
*/
for (; lcd->addr.x < lcd->width; lcd->addr.x++)
lcd->ops->print(lcd, ' ');
lcd->addr.x = 0;
lcd->addr.y = (lcd->addr.y + 1) % lcd->height;
lcd->ops->gotoxy(lcd, lcd->addr.x, lcd->addr.y);
break;
case '\r':
/* go to the beginning of the same line */
lcd->addr.x = 0;
lcd->ops->gotoxy(lcd, lcd->addr.x, lcd->addr.y);
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_display(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 (((count + 1) & 0x1f) == 0) {
/*
* charlcd_write() is invoked as a VFS->write() callback
* and as such it is always invoked from preemptible
* context and may sleep.
*/
cond_resched();
}
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 = charlcd_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) {
priv->lcd.ops->clear_display(&priv->lcd);
priv->must_clear = false;
priv->lcd.addr.x = 0;
priv->lcd.addr.y = 0;
}
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 (((count + 1) & 0x1f) == 0)
cond_resched();
charlcd_write_char(lcd, *tmp);
}
}
#ifdef CONFIG_PANEL_BOOT_MESSAGE
#define LCD_INIT_TEXT CONFIG_PANEL_BOOT_MESSAGE
#else
#define LCD_INIT_TEXT "Linux-" UTS_RELEASE "\n"
#endif
#ifdef CONFIG_CHARLCD_BL_ON
#define LCD_INIT_BL "\x1b[L+"
#elif defined(CONFIG_CHARLCD_BL_FLASH)
#define LCD_INIT_BL "\x1b[L*"
#else
#define LCD_INIT_BL "\x1b[L-"
#endif
/* initialize the LCD driver */
static int charlcd_init(struct charlcd *lcd)
{
struct charlcd_priv *priv = charlcd_to_priv(lcd);
int ret;
priv->flags = ((lcd->height > 1) ? LCD_FLAG_N : 0) | LCD_FLAG_D |
LCD_FLAG_C | LCD_FLAG_B;
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 = lcd->ops->init_display(lcd);
if (ret)
return ret;
/* display a short message */
charlcd_puts(lcd, "\x1b[Lc\x1b[Lb" LCD_INIT_BL LCD_INIT_TEXT);
/* clear the display on the next device opening */
priv->must_clear = true;
charlcd_home(lcd);
return 0;
}
struct charlcd *charlcd_alloc(void)
{
struct charlcd_priv *priv;
struct charlcd *lcd;
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (!priv)
return NULL;
priv->esc_seq.len = -1;
lcd = &priv->lcd;
return lcd;
}
EXPORT_SYMBOL_GPL(charlcd_alloc);
void charlcd_free(struct charlcd *lcd)
{
kfree(charlcd_to_priv(lcd));
}
EXPORT_SYMBOL_GPL(charlcd_free);
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 = {
.notifier_call = panel_notify_sys,
};
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 = charlcd_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, CHARLCD_OFF);
}
return 0;
}
EXPORT_SYMBOL_GPL(charlcd_unregister);
MODULE_LICENSE("GPL");