First commit

Makefile

@@ -0,0 +1,11 @@
+ifneq ($(KERNELRELEASE),)
+   obj-m := hitachi-lcd.o
+else
+   KERNELDIR ?= /lib/modules/$(shell uname -r)/build
+   PWD := $(shell pwd)
+
+default:
+	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
+clean:
+	$(MAKE) -C $(KERNELDIR) M=$(PWD) clean
+endif

hitachi-lcd.c

@@ -0,0 +1,274 @@
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/gpio/consumer.h>
+#include <linux/miscdevice.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+
+/* Simple device driver
+ * for the Hitachi HD44780U LDC */
+
+#define MODULE_NAME "hitachi-lcd"
+
+#define CMD_TIME_START (40) /* 40 usec */
+#define CMD_TIME_END (50)
+
+#define DISPLAY_ON 1
+#define DISPLAY_OFF 0
+#define CURSOR 1
+#define NO_CURSOR 0
+#define BLINK 1
+#define NO_BLINK 0
+#define LINES_2 1
+#define LINES_1 0
+#define LCD_MAX_CHARS 40
+
+#define BUF_SIZE 32
+
+static DEFINE_MUTEX(hitachi_lcd_lock);
+struct hitachi_lcd {
+    struct gpio_desc *data[4];
+    struct gpio_desc *rs;
+    struct gpio_desc *rw;
+    struct gpio_desc *e;
+    char *buf;
+    unsigned short index;
+};
+
+static struct hitachi_lcd lcd;
+
+/* module params */
+static int modeset = 1;
+static int max_chars = LCD_MAX_CHARS;
+/* Pins use BCM Numbering */
+static int pin_d4 = 5;
+static int pin_d5 = 6;
+static int pin_d6 = 12;
+static int pin_d7 = 13;
+static int pin_rs = 16;
+static int pin_rw = 26;
+static int pin_e = 25;
+module_param(modeset, int, 0444);
+module_param(pin_d4, int, 0444);
+module_param(pin_d5, int, 0444);
+module_param(pin_d6, int, 0444);
+module_param(pin_d7, int, 0444);
+module_param(pin_rs, int, 0444);
+module_param(pin_rw, int, 0444);
+module_param(pin_e, int, 0444);
+
+static struct gpio_desc *init_gpio_out(unsigned int n)
+{
+    struct gpio_desc *gpio;
+    gpio = gpio_to_desc(n);
+    if (IS_ERR(gpio)) {
+	pr_err("hitachi-lcd: failed gpio %d allocation\n", n);
+	return NULL;
+    }
+    if (gpiod_direction_output(gpio, GPIOD_OUT_LOW)) {
+	pr_err("hitachi-lcd: failed set gpio direction\n");
+	gpiod_put(gpio);
+	return NULL;
+    }
+    return gpio;
+}
+
+static void put_gpios(struct hitachi_lcd *lcd)
+{
+    int i;
+    for (i = 0; i < 4; i++) {
+	if (lcd->data[i])
+	    gpiod_put(lcd->data[i]);
+    }
+    if (lcd->rs)
+	gpiod_put(lcd->rs);
+    if (lcd->rw)
+	gpiod_put(lcd->rw);
+    if (lcd->e)
+	gpiod_put(lcd->e);
+}
+
+static void clear_data_gpios(struct hitachi_lcd *lcd)
+{
+    gpiod_set_value(lcd->data[0], 0);
+    gpiod_set_value(lcd->data[1], 0);
+    gpiod_set_value(lcd->data[2], 0);
+    gpiod_set_value(lcd->data[3], 0);
+}
+
+static void clear_all_gpios(struct hitachi_lcd *lcd)
+{
+    clear_data_gpios(lcd);
+    gpiod_set_value(lcd->rs, 0);
+    gpiod_set_value(lcd->rw, 0);
+    gpiod_set_value(lcd->e, 0);
+}
+
+static void send_command(struct hitachi_lcd *lcd)
+{
+    gpiod_set_value(lcd->e, 1);
+    usleep_range(CMD_TIME_START, CMD_TIME_END);
+    gpiod_set_value(lcd->e, 0);
+}
+
+static void set_display(struct hitachi_lcd *lcd, unsigned display,
+	unsigned cursor, unsigned blink)
+{
+    clear_all_gpios(lcd);
+    send_command(lcd);
+    gpiod_set_value(lcd->data[3], 1);
+    gpiod_set_value(lcd->data[2], display);
+    gpiod_set_value(lcd->data[1], cursor);
+    gpiod_set_value(lcd->data[0], blink);
+    send_command(lcd);
+}
+
+static void setmode_4bit(struct hitachi_lcd *lcd,
+	unsigned line_no)
+{
+    clear_all_gpios(lcd);
+    gpiod_set_value(lcd->data[1], 1);
+    send_command(lcd);
+    send_command(lcd);
+    gpiod_set_value(lcd->data[3], line_no);
+    send_command(lcd);
+}
+
+static void clear_display(struct hitachi_lcd *lcd)
+{
+    clear_all_gpios(lcd);
+    send_command(lcd);
+    gpiod_set_value(lcd->data[0], 1);
+    send_command(lcd);
+}
+
+static void entry_mode_set(struct hitachi_lcd *lcd)
+{
+    clear_all_gpios(lcd);
+    send_command(lcd);
+    gpiod_set_value(lcd->data[1], 1);
+    gpiod_set_value(lcd->data[2], 1);
+    send_command(lcd);
+}
+
+static void lcd_putchar(struct hitachi_lcd *lcd, char c)
+{
+    int i;
+
+    clear_all_gpios(lcd);
+    /* 1st nibble */
+    gpiod_set_value(lcd->rs, 1);
+    for (i = 4; i < 8; i++) {
+	gpiod_set_value(lcd->data[i-4], (c & (1<<i)) >> i );
+    }
+    send_command(lcd);
+
+    /* 2nd nibble */
+    for (i = 0; i < 4; i++) {
+	gpiod_set_value(lcd->data[i], (c & (1<<i)) >> i );
+    }
+    send_command(lcd);
+}
+
+static void lcd_puts(struct hitachi_lcd *lcd, char *s, size_t size)
+{
+    int i;
+    for (i = 0; i < size; i++) {
+	if (lcd->index > max_chars) {
+	    lcd->index = 0;
+	    clear_display(lcd);
+	    msleep(100);
+	}
+	if (s[i] == '\n')
+	    continue;
+	lcd_putchar(lcd, s[i]);
+	lcd->index++;
+    }
+}
+
+ssize_t lcd_write(struct file *file, const char __user *from,
+	size_t size, loff_t *off)
+{
+    size_t read_size;
+
+    if (size < 1)
+	return size;
+    mutex_lock(&hitachi_lcd_lock);
+    read_size = simple_write_to_buffer(lcd.buf, size,
+	    off, from, BUF_SIZE);
+    if (read_size > 0) {
+	lcd_puts(&lcd, lcd.buf, read_size);
+    }
+    mutex_unlock(&hitachi_lcd_lock);
+    return read_size;
+}
+
+static struct file_operations lcd_ops = {
+    .write = lcd_write,
+    .read = NULL,
+};
+
+static struct miscdevice lcd_device = {
+    .minor = MISC_DYNAMIC_MINOR,
+    .name = MODULE_NAME,
+    .fops = &lcd_ops,
+    .mode = 0222,
+};
+
+static int __init hitachi_lcd_load(void)
+{
+    int i;
+
+    /* lcd char buffer */
+    lcd.buf = kmalloc(BUF_SIZE, GFP_KERNEL);
+    if (!lcd.buf)
+	return -ENOMEM;
+
+    lcd.data[0] = init_gpio_out(pin_d4); /* D4 */
+    lcd.data[1] = init_gpio_out(pin_d5); /* D5 */
+    lcd.data[2] = init_gpio_out(pin_d6); /* D6 */
+    lcd.data[3] = init_gpio_out(pin_d7); /* D7 */
+    lcd.rs = init_gpio_out(pin_rs); /* RS */
+    lcd.rw = init_gpio_out(pin_rw); /* RW */
+    lcd.e = init_gpio_out(pin_e); /* E */
+    lcd.index = 0; /* next position in the lcd */
+
+    /* check correct init of gpios */
+    if (!lcd.rs || !lcd.rw || !lcd.e)
+	goto cleanup;
+    for (i = 0; i < 4; i++) {
+	if (!lcd.data[i])
+	    goto cleanup;
+    }
+    /* init display */
+    /* set modeset to 0 if the display
+     * has not been HW reinit */
+    if (modeset)
+	setmode_4bit(&lcd, LINES_1);
+    set_display(&lcd, DISPLAY_ON, CURSOR, BLINK);
+    entry_mode_set(&lcd);
+    clear_display(&lcd);
+    misc_register(&lcd_device);
+    return 0;
+
+cleanup:
+    kfree(lcd.buf);
+    put_gpios(&lcd);
+    misc_deregister(&lcd_device);
+    return -EIO;
+}
+
+static void __exit hitachi_lcd_unload(void)
+{
+    kfree(lcd.buf);
+    set_display(&lcd, DISPLAY_OFF, NO_CURSOR, NO_BLINK);
+    clear_display(&lcd);
+    put_gpios(&lcd);
+    misc_deregister(&lcd_device);
+}
+
+module_init(hitachi_lcd_load);
+module_exit(hitachi_lcd_unload);
+
+MODULE_AUTHOR("Antonio Cardace <[email protected]>");
+MODULE_LICENSE("GPL v2");