drivers: auxdisplay: hd44780: rework auxdisplay_hd44780_command()

Make this function more concise in order to introduce busy-flag polling
mechanism later on.

Signed-off-by: Jan Kuliga <[email protected]>

Author: kuliga

drivers/auxdisplay/auxdisplay_hd44780.c

@@ -77,41 +77,33 @@ struct auxdisplay_hd44780_config {
 static void auxdisplay_hd44780_set_entry_mode(const struct device *dev);
 static void auxdisplay_hd44780_set_display_mode(const struct device *dev, bool enabled);
 
+static void hd44780_pulse_enable_line(const struct device *dev)
+{
+	const struct auxdisplay_hd44780_config *const config = dev->config;
+
+	gpio_pin_set_dt(&config->e_gpio, 1);
+	k_sleep(K_USEC(config->enable_line_rise_delay));
+	gpio_pin_set_dt(&config->e_gpio, 0);
+	k_sleep(K_USEC(config->enable_line_fall_delay));
+}
+
 static void auxdisplay_hd44780_command(const struct device *dev, bool rs, uint8_t cmd,
 				       uint8_t mode)
 {
 	const struct auxdisplay_hd44780_config *config = dev->config;
 	int8_t i = 7;
-
-	if (mode == AUXDISPLAY_HD44780_MODE_8_BIT) {
-		while (i >= 0) {
-			gpio_pin_set_dt(&config->db_gpios[i], ((cmd & BIT(i)) ? 1 : 0));
-			--i;
-		}
-	} else {
-		while (i >= 4) {
-			gpio_pin_set_dt(&config->db_gpios[i], ((cmd & BIT(i)) ? 1 : 0));
-			--i;
-		}
-	}
+	const int8_t lsb_line = (mode == AUXDISPLAY_HD44780_MODE_8_BIT) ? 0 : 4;
+	int8_t ncommands = (mode == AUXDISPLAY_HD44780_MODE_4_BIT) ? 2 : 1;
 
 	gpio_pin_set_dt(&config->rs_gpio, rs);
 
-	gpio_pin_set_dt(&config->e_gpio, 1);
-	k_sleep(K_USEC(config->enable_line_rise_delay));
-	gpio_pin_set_dt(&config->e_gpio, 0);
-	k_sleep(K_USEC(config->enable_line_fall_delay));
-
-	if (mode == AUXDISPLAY_HD44780_MODE_4_BIT) {
-		while (i >= 0) {
-			gpio_pin_set_dt(&config->db_gpios[(i + 4)], ((cmd & BIT(i)) ? 1 : 0));
+	while (ncommands--) {
+		for (int8_t line = 7; line >= lsb_line; --line) {
+			gpio_pin_set_dt(&config->db_gpios[line], ((cmd & BIT(i)) ? 1 : 0));
 			--i;
 		}
 
-		gpio_pin_set_dt(&config->e_gpio, 1);
-		k_sleep(K_USEC(config->enable_line_rise_delay));
-		gpio_pin_set_dt(&config->e_gpio, 0);
-		k_sleep(K_USEC(config->enable_line_fall_delay));
+		hd44780_pulse_enable_line(dev);
 	}
 }